A MODIFIED FORCE-RESTORE APPROACH TO MODELING SNOW-SURFACE HEAT FLUXES - Luce, C. H.; Tarboton, D.G. (69th Annual Western Snow Conference, 2001)
Accurate modeling of the energy balance of a snowpack requires good estimates of the snow surface temperature. The snow surface temperature allows a balance between atmospheric heat fluxes and the conductive flux into the snowpack. While the dependency of atmospheric fluxes on surface temperature is reasonably well understood and parameterized, conduction of heat from the snow surface into the snowpack depends on a complex history of previous heat exchanges and surface temperatures and can be somewhat more difficult to model. A variety of schemes ranging from multiplayer finite difference models to simple approximations based on air temperature exist to estimate snow surface temperatures and conductive fluxes. Previous research has suggested that single layer models are incapable of dealing with the complexity of the heat flow calculations within a snowpack. In this paper, we explore the idea of describing heat fluxes into the snowpack based on knowledge of the diurnal forcing. We examine observations of snow temperatures within a snowpack in detail and compare heat fluxes estimated from a linear equilibrium approach, a force restore approach, and a modification of the force- restore approach that estimates the effects of lower frequency temperature variations on the surface heat flux. The modified force restore model shows the best agreement with observations.
Keywords: Modeling, Energy balance, Snowpack, Diurnal forcing

THE EFFECT OF VARIABLE PATTERNS OF SNOW DEPOSITION AND DRIFTING ON SNOWMELT, RUNOFF, AND STREAM DISCHARGE IN A SEMI-ARID MOUNTAIN BASIN - Marks, D.; Winstral, A. (69th Annual Western Snow Conference, 2001)
In semi-arid mountainous regions, local topography and canopy cover strongly affect wind patterns during storms which alters snow distribution and causes the development of hydrologically significant drifts. While large drifts may cover only 5—15% of the basin area, they can hold 50% or more of the basin SWE at peak accumulation and 75—100% of the basin SWE in late spring. Snowmelt from the drifts provides essentially the only source of water to the basin in late spring and early summer, and therefore directly affects basin ecology, runoff response, and the basin hydrograph. To understand how snow distribution and drifting affect the timing and magnitude of snowmelt and the delivery of melt- water to the stream, we simulate both the patterns of snow deposition and melt over a small headwater basin in the Owyhee Mts. (the Reynolds Mountain East basin (0.36 kin2)) using the energy balance snowmelt model ISNOBAL. Simulations were run for several snow seasons in the 1980’s for which time-series aerial photos monitoring of the location and depletion of snow drifts during melt-out were available. Precipitation input was modeled as a function of topographic exposure relative to storm-event winds and the difference in storm-event catch between a sheltered site and an exposed site. Snowcover in the modeled drift zones lasted well into the spring and showed good agreement with drift assessments made from time-series late-season aerial photography. This experiment shows that disparate patterns of snow deposition and melt, including the effect of drifting, which is typical of semi-arid mountain basins, can be modeled as a function of terrain and vegetation.
Keywords: Reynolds Creek, Snow covered area, Snow distribution

SNOWPACK COMPARISONS BETWEEN AN OPENING AND A LODGEPOLE PINE STAND - McCaughey, W.W.; Farnes, P.E. (69th Annual Western Snow Conference, 2001)
In the fall of 1993, two snow pillows were installed at a permanent data site located at Onion Park Research Natural Area on the Tenderfoot Creek Experimental Forest in central Montana. One pillow is located in a small open meadow, and the second pillow is located 25 m away under a dense forest canopy of lodgepole pine. The two pillows were installed to standard specifications for a Natural Resources Conservation Service snow telemetry data site. Measurements of snow water equivalent (SWE) were monitored on both pillows with a continuous water level recorder from 1993 through 1995 and electronic data recorder from 1995 to present. Manual manometer levels were read during each site visit to verify data recorder values. The annual maximum SWE on the canopy pillow has averaged 77 percent of the open pillow over the winters from 1993 to 2000. Melt rates under the canopy have averaged 46 percent of that in the open. On average, final melt-out of the canopy pillow is 9 days after the open pillow. Results from this research will be used to model changes in streamfiow volume and timing of peak streamflow after forest modifications in 2001. This information should also be usefUl for hydrologic modeling or for modeling hydrologic changes after a forest has been harvested, burned or changed in structure due to age, disease, insect infestations or blowdown.
Keywords: Snow in forest, Snow in opening, Snow pillow

ANALYSIS OF THE SPATIAL VARIABILITY OF SNOW COVER DEPLETION IN AN ALPINE WATERSHED, TOKOPAH BASIN, SIERRA NEVADA, CALIFORNIA, U.S.A. - Molotch, N.P.; T H Painter; Colee, M.T.; Rosenthal, W.; Dozier, J.; Bales, R.C. (69th Annual Western Snow Conference, 2001)
In this study we quantified the spatial and temporal depletion of snow covered area (SCA) in order to obtain estimates of peak snow water equivalence (SWE) in the 19.1 km2 Tokopah Basin. We sought to answer the following questions: How do we improve the use of snow cover depletion curves by incorporating additional data and spatial analysis? How can we use snow cover depletion curves to estimate peak SWE earlier in the snowmelt season and continue to have leverage to update our estimates throughout the ablation season? What meteorological fields or combination of meteorological fields yield the most leverage in updating SWE estimates? In order to quantify snow cover depletion at different elevations and under different topographic environments, we analyzed snow cover depletion patterns in different elevation zones and in sub-basins of varying topographic heterogeneighty. We used 30m remotely sensed SCA data, hourly meteorological data, ground-based surveys of SWE and a 30m digital elevation model (DEM). We generated depletion curves of SCA using two methods of varying complexity: SCA versus modeled accumulated degree-days and SCA versus modeled net radiation. We found that SWE over the basin during the April, May and June snow surveys was 995mm, 701mm and 283mm respectively. Degree-day accumulation produced decreases in SCA at lower elevations (<2823m) before SCA decreased at higher elevations (>3222m). Degree-day depletion curves did not represent observed temporal variability in SWE during the ablation season. Depletion curves using net radiation as the response variable proved to better represent temporal SWE variability. We found that incremental decreases in SCA at higher elevations (>3222m) resulted in a greater decrease of SWE than the corresponding SWE decrease at lower elevations (<2 82 3m)
Keywords: Snow covered area, Spatial variability, Tokopah Basin

ANTHROPOGENIC CLIMATE CHANGE AND SNOW IN THE PACIFIC NORTHWEST - Mote, P.W.; Hamlet, A.F. (69th Annual Western Snow Conference, 2001)
The Pacific Northwest is unusually vulnerable to a warning climate owing to its heavy reliance on snowpack to store water for summer use. This paper outlines the state of global climate science and describes efforts by the Climate Impacts Group at the University of Washington to understand how a warming, of plausible magnitude could affect the Pacific Northwest, specifically with regard to streamflow and snowpack.
Keywords: climate change

USING GIS TO PREDICT THE SPATIAL DISTRIBUTION OF PERENNIAL SNOW UNDER MODERN AND LATE PLEISTOCENE CONDITIONS IN TIlE SNAKE RANGE, NEVADA - Orddorff, R.L.; Van Hoesen, J.G. (69th Annual Western Snow Conference, 2001)
ELApse is a climate-driven snow and ice model developed to estimate the spatial distribution of perennial snow and ice in alpine systems. The snow model computes monthly snowfall, snowmelt, and resulting snowpack at each grid cell, and it estimates the densification of perennial snowpack and its transformation into glacial ice when appropriate. The model proceeds year-by-year until monthly snow and ice totals equilibrate. ELApse is sensitive to latitudinal and elevational controls on climate, but it is insensitive to subtle variations in the land surface that create microclimates that tend to preserve snow and ice. We use ArcView GIS to identify terrain characteristics (such as shading, slope, and curvature) that enhance accumulation and preservation of snow and ice. ELApse estimates of modem perennial snow extent in the high peaks of the southern Snake Range, NV are greatly improved by GIS postprocessing. In addition to modern solutions, we estimate the spatial distribution of perennial snow for temperature perturbations of -2C, -4C, and -6C.
Keywords: GIS, Snow covered area, Spatial distribution

MAPPING SNOW ALGAE CONCENTRATIONS IN THE SIERRA NEVADA WITH IMAGING SPECTROSCOPY - T H Painter; Duval, B.; Thomas, W.H.; Mendez, M.; Heintzleman, S.; Dozier, J. (69th Annual Western Snow Conference, 2001)
We present spectral reflectance measurements of algal snow and a model to retrieve snow algal concentration from imaging spectrometer data collected in the Tioga Pass region of the Sierra Nevada, California. Spectral reflectance measurements of snow containing the algae Chlamydomonas Nivalas exhibit carotenoid absorption in the wavelength range 0.4 — 0.58 pm and chlorophyll—a,-b absorption in the wavelength range 0.6 — 0.7 pm. The integral of the scaled chlorophyll-a,-b absorption feature, 1680, varies with algal concentration, Ca. The relationship appears to be exponential but this model is not yet statistically significant due to limited data at high concentrations. Using the relationship, Ca = 922.61 exp(13.56 Isub680), we inverted Airborne Visible Imaging Spectrometer (AVIRIS) data for algae concentration. In the 5.5 km , imaged region, the mean algal concentration was 880 cells/mL with a standard deviation of 1445 cells/mL. We calculated the total imaged algal biomass, Ba = 11.1 kg. From the field spectral measurements, we fit a model relating snow albedo, AsubS, to Ca. We inverted algae concentration images for albedo using this model. Mean retrieved albedo was 0.595 with a standard deviation of 0.009, a minimum of 0.43, and a maximum of 0.62.
Keywords: Simulation modeling, Snow algae

TELEMETRY AND THE INTERNET - Schaefer, G.; Sytsma, D. (69th Annual Western Snow Conference, 2001)
This paper provides an overview of recent advances in wireless telemetry and Internet browser technology for the collection and distribution of water, weather and climate data. Comparisons between performance, data reliability and life cycle costs are presented for the various options that are available to the user for routing data from a remote site to a desktop browser.The choice between using satellite, cellular, meteor burst and various VHF/UHF technologies is not always clear cut and involves a trade-off between geographic coverage, latency of data and network service fees. This paper provides guidelines and figures of merit to assist the user in choosing an appropriate wireless technology.Web based access to remote sites is becoming a very cost effective means of collecting, archiving and displaying hydrometeorological data using a desktop PC. Remote station configuration, security, data basing and text messaging are topics that are discussed.Finally, cooperative arrangements between government and industry are becoming more common place to take advantage of the various telemetry and browser technologies that are being used by these various agencies. A cooperative venture between Natural Resources Conservation Service (NRCS) and Meteor Communications Corporation (MCC) in Stoneville, Mississippi is described as an example of this trend.
Keywords: Data collection, Data distribution, Data reliability

MANAGING SNOW TO IRRIGATE SHELTERBELTS AND ABATE SALINITY - Steppuhn, H. (69th Annual Western Snow Conference, 2001)
Two techniques for extracting near-surface ground water were evaluated on a one-hectare (2.5-acre) salinized parcel of agricultural land situated within a barley field located in Saskatchewan. A mound of ground water formed under the parcel each spring as subsurface waters encountered impediments to downslope flow. This resulted in a near-surface watertable which subjected the parcel to salinization. The remedial technique involved extracting the excess ground water and utilizing it to irrigate shelterbelt vegetation planted for wildlife and agro-forestry benefit. Lowering the watertable reduced salinization and encouraged snow management to enhance total water supply. Upon infiltration, the additional water from melting snow could leach more of the offending salts from the parcel’s root zones. Water supplies were enhanced by retaining wind-blown snow within tall wheatgrass windbreaks seeded adjacent to the parcel. Sites rich in ground water, such as the parcel studied, can be de-watered either by gravity drainage or by solar-powered pumping using one or more shallow wells and, if necessary, radial accumulation galleries. The concept of water harvesting features simple, low-cost systems that can readily be installed by land owners using a backhoe. Water harvested by these systems could be used for livestock, wildlife, waterfowl, salt-tolerant field crops, and shelterbelts.
Keywords: Leaching, Snow management

INCORPORATING SEASONAL STREAMFLOW FORECASTS INTO OPERATIONAL DECISIONMAKING - Waage, M.D.; Baldwin, C.K.; Steger, R.G.; Bray, T.J. (69th Annual Western Snow Conference, 2001)
Note: This paper is a companion to SEASONAL STREAMFLOW FORECASTING USING CLIMATE INFORMATION (Baldwin, this volume).Explosive population growth in the western U.S. and the resulting new demands on water systems require water system operators to squeeze more efficiency from their existing water systems. In mountainous areas of the west, most of the available water comes from snowmelt runoff. Improving snowmelt forecasting, including the lead-time of forecasts, can help meet the water challenges of population growth.One technique, developed by Utah State University for the city of Denver, shows promise. Based on climate indices from the Pacific and Atlantic oceans, probabilistic forecasts of the April through July runoff volume on the South Platte and Colorado rivers are made in the autumn. These forecasts have the potential to increase operating efficiency particularly to benefit secondary operating priorities such as hydropower generation, water- based recreation, and aquatic restoration programs. The forecasts are now being evaluated for use in operational decisionmaking. Forecasts made in the fall of 2000 along with the low water conditions prompted system operators to reduce winter hydropower generation and redistribute storage water. Spring runoff will show if these were good decisions. Research will continue this year into how to make the forecasts more understandable and useable by the water system operators.
Keywords: Operational forecasting, Probabilistic forecasting

2000 Title, Contents, and Minutes (68th Annual Western Snow Conference, 2000)

An enhanced technique for a more reliable daily snow measurements with an antifreeze-based tipping bucket gauge - Carcoana, R.; Enz, J.W. (68th Annual Western Snow Conference, 2000)
The record snowfall during the 1996-1997 winter season and subsequent spring flood stressed the need for a suitable method to measure daily snowfall at all 52 North Dakota Agricultural Weather Network (NDAWN) stations. Our goal was to obtain accurate daily winter precipitation values from a remote automatic weather station. In November 1997, a system comprised of a Texas Electronics TE5253 rain gauge with a Campbell Scientific CS705 antifreeze based snow adapter, suitable for obtaining a reasonable estimate of the total seasonal precipitation (McCaughey and Fames, 1996), was installed at Fargo, North Dakota NDAWN station. Laboratory testing identified an antifreeze overflow restriction and a system support problem. We redesigned the shape of the overflow tube and added surfactant to the antifreeze mixture to diminish surface tension. We installed a weight support (tripod) and a side post to increase gauge stability in windy conditions and maintain a plumb position. The new system was tested during the second half of the 1997-98 winter, and the 1998-99 and 1999-2000 v.inter seasons. Comparative data for each snow precipitation event were recorded, collected and analyzed from three different sources: NWS Coop observer located about two miles E, a standard NWS universal Belfort weighing gauge, and the adjacent TE525/CS705 tipping bucket gauge/snow adapter at the Fargo, NDAWN station. The combination of the new overflow tube design, added surfactant and a reliable support system, enhanced the flow timing and provided more reliable daily totals.
Keywords: Instrumentation, Precipitation gauge, Snow instrumentation, Snow measurement, Tipping bucket

Focus on the upper basins of the Dungeness river system - Clark, W.; Clark, V. (68th Annual Western Snow Conference, 2000)
A poster presented at the conference characterizes the upper watersheds of the Dungeness River and its Gray Wolf River tributary located on the northeastern Olympic Peninsula of Washington State. The short, steep river system traverses 30+ miles from its headwaters in 7,000 ft + ridges of the Olympic Mountains to sea level in the Strait of Juan de Fuca. Until recently upper elevation climate data hadbeen limited to monthly reporting from three snow courses in the proximity of the northwest comer of the watershed. Three Snotel sites are now operational in the northeast Olympics that provide telemetry reporting of temperature, precipitation, and snowpack data, summarized here.
Keywords: Olympic Peninsula, SNOTEL

A high-resolution distributed snowmelt model in an alpine catchment - Colee, M.T.; T H Painter; Rosenthal, W.; Dozier, J.C. (68th Annual Western Snow Conference, 2000)
We run a physically based snowmelt model (SNTHERM.89) for each 30 m pixel in the Tokopah Valley, an alpine catchment in the Sierra Nevada of California. We use extensive field surveys to initialize and validate the distributed model (MrSNTHERM). We initialize with an April 1997 survey, as close to maximum snow accumulation as possible, and then compare the model results to a second survey in May 1997. Spatially distributed depth and density measurements were collected along a grid during these field surveys, and we use them to interpolate the initial snow surface. We derive initial snow-covered area (SCA) from Thematic Mapper (TM) data and albedo and surface grain size from Airborne Visible Infrared Imaging Spectrometer (A VIRIS) data. Meteorological data at hourly time steps from three stations within the basin are distributed over the basin based on observed lapse rates. Hourly solar radiation inputs to the model are calculated with the topographically corrected clear-sky radiation model TOPORAD and adjusted for cloud cover based on measured solar radiation from twosites in the basin. Hourly incoming longwave radiation is calculated from distributed temperature and relative humidity surfaces and is validated with measurements at two of the three meteorological stations. We evaluate model performance by comparing its outputs with the May field measurements of depth and density, AVIRIS derived snow cover and grain size, and TM-derived snow cover. To assess the accuracy of the model's snowmelt calculation, we compare them to measured basin hydrographs in two sub-basins as well as the entire basin.
Keywords: Model, Snowmelt, Spatially distributed model

Life after ASOS (Automated Surface Observing System) -- Progress in National Weather Service snow measurement - Doesken, N.J.; McKee, T.B. (68th Annual Western Snow Conference, 2000)
The National Weather service is the primary source for snow measurements for areas of our country where most people live and work. Through its networks of first-order and cooperative stations, snowfall data are available for nearly every county of our country dating back many decades.Important changes have occurred in NWS weather observations that are affecting the continuityof snowfall data. The single greatest change was the deployment of the Automated Surface Observing System (ASOS) at hundreds of airport weather stations across the country during the 1990s. ASOS does not measure snowfall or snow depth. It utilizes a heated tipping bucket rain gauge for measuring both rain and the water content of snow. This type of gauge tends to under measure the water content of precipitation that falls as snow, especially at temperatures well below the freezing point.New snow measurement guidelines were implemented in 1996 to expand the use and consistency of snow data from cooperative observers. These guidelines allow snowfall measurements at intervals of no less than once daily to no more than once every six hours. Data were collected for two winters at volunteer locations in several states to assess the impact of measurement interval on measured snowfall. Results show that the time interval between measurements does affect the reported snowfall totals. Measurements taken every six hours produced snowfall totals 19% greater than measurements taken once each day. Similarly, measurements taken every hour produced snowfall totals 15' greater than if measured only once at the end of each 6-hour period. This suggests that data users must beware of this characteristic before analyzing time series or spatial snowfall patterns from different types of weather stations.
Keywords: Automated observation system, Snow measurement

USGS research on three mid-latitude glaciers - Green, J.R.; Cecil, L.D.; Naftz, D.L.; Schuster, P.F. (68th Annual Western Snow Conference, 2000)
Low- and mid-Iatitude regions of the earth are home to 80 to 90 percent of the world's population. Because of this, the U.S. Geological Survey (USGS) is conducting a research program to study the geochemistry of precipitation' snow, ice, and runoff samples from mid-latitude glaciers in Kyrghyzstan, Nepal, and the United States. Areas of research, such as ground-water studies, reconstructing paleoclimate records, describing anthropogenic input of chemicals to the environment, and modeling global climate change, are important to the well being of the worlds' population and can be supplemented by the collection and chemical analysis of snow and ice cores. Nearly all the constituents that compose snow and ice-core samples contribute vital information, whether it be the microbial communities that flourish in snow, radionuclides present in various amounts in all the samples, or location-specific deposits of mercury and nitrate. This work is hastened by the fact that mid-Iatitude glaciers, and the information preserved in them, are rapidly disappearing as a result of global warming. Research collabomtion for this project includes 12 national and 7 international universities, and 4 government agencies. Funding is provided by the National Science Foundation, the U.S. Department of Energy, and the USGS.
Keywords: Climate change, Geochemistry, Glaciers, Modeling, Paleoclimate

Effects of inter-annual and decadal-scale climate variability on Winter and Spring streamflow in western Oregon and Washington - Koch, R.W.; Fisher, A.R. (68th Annual Western Snow Conference, 2000)
River basins in western Oregon and Washington that have a seasonal snowpack exhibit a dual-peaked hydro graph. The early peak is due to the winter maximum rainfall occurring at lower elevations and the later one is due to snowmelt. Three such basins were examined to determine whether the distribution of streamflow within the year is related to indices of either inter-annual (as measured by the Southern Oscillation Index, SOl) or inter-decadal (as measured by the Pacific Decadal Oscillation, PDO) variability in the climate. The relationship of streatnflow to SOl is affected by the phase of the PDO. During below average phases of the PDO (generally warm SST's in the north Pacific Ocean, except along the North American coast). streamflow exhibits a significant relationship to SOl. where as during the above average phase. there is no statistically significant relationship between streamflow and SOl. Statistically significant differences in the distribution of flow within the year were also noted and were related to the phase of the PDO.
Keywords: Climate change, SOI

Long-lead precipitation outlook augmentation of multi-variate linear regression streamflow forecasts - Modini, G.C. (68th Annual Western Snow Conference, 2000)
Decisions based on monthly streamflow forecasts (multi-variate linear regression models) that utilize precipitation, antecedent streamflow, snow water equivalent and the Southern Oscillation Index, can have major implications particularly during extreme runoff years. In this study, long-Iead precipitation outlooks were used in an effort to augment the regression models for better decision making during extreme runoff years. Blue River Lake Inflow in the Willamette River Basin was used as a inflow forecast point. A precipitation station was selected for application of the long-Iead outlooks Regression analysis was performed and new regression equations were computed. A Gamma distribution was applied to quantify the outlooks. A range of hypothetical forecasts was generated and total standard errors were compared.15 of the 17 monthly regression models using the outlooks showed a reduction in total standard errors with the biggest reductions occurring for the more extreme forecasts. Therefore, results prove that using the outlooks can indeed result in greater accuracy for streamflow forecasts particularly during extreme runoff years. The new regression equations were then compared against the old equations for the 1999 water year which was a record snowpack year for the Willamette River Basin. It is concluded that the use oflong-lead climate outlooks could have provided better decision making early in the forecast season for the operation of Blue River reservoir.
Keywords: Forecasting, Multi-variate analysis, Regression mocels

Investigating periodicity in the long term precipitation record of Donner Summit, California - Osterhuber, R.J.; Clark, W.; Clark, V.; Colee, M.T. (68th Annual Western Snow Conference, 2000)
Donner Summit, California has the longest precipitation record from any high-elevation snow-dominated environment in the western United States. Water year 2000 will complete its 13Oth year of record. Ancedotal evidence suggests periodic trends in the long term snowfall record of Donner Summit. However, the measurement of snowfall is frequency dependent, making it a less-than-ideal gauge by which to compare one season to another. Correlation coefficients are derived between annual Donner Summit precipitation values X(t) and X(t+k), where k is delta t. These coefficients are combined with a periodic term to derive a spectral density which describes the amount of variance per interval of frequency within the historic record. Peak frequencies from the spectral analysis are applied to the historic data to test for periodicity. The relative strength (or weakness) of periodic cycles may improve perspective on long term trends in mountain weather, vital information for water managers.
Keywords: Periodicity, Precipitation variability, Snowfall measurement

Automated spectro-goniometer: A robitic arm for the measurement of snow bi-directional reflectance distribution function - T H Painter; Paden, B.E.; Dozier, J. (68th Annual Western Snow Conference, 2000)
We describe the UCSB Automated Spectro-Goniometer (ASG), a two-axis robotic arm paired with a field spectroradiometer for the rapid and accurate measurement of the optical bi-directional reflectance distribution function (BRDF) of snow. Improvements in radiative transfer models and remote sensing algorithms for snow properties require a more accurate characterization of the angular distribution of reflectance of snow. Previous measurements of snow BRDF have been incomplete with respect to one or more of spectral range, spectral resolution, angular resolution and sampling, solar zenith sampling, and snow characterization. The kinematics of the ASG may be described by Rodrigues ' fonnula for a 2 degree of freedom arm. We describe the forward kinematics for the ASG and then solve the inverse problem from given view angle to necessary rotation about each axis. Its two-dimensional hemispheric sampling space facilitates the measurement of spectral reflectance from snow into any direction. The ASG will usually sample a 10deg hemispheric grid at a 0.5 Hz sampling rate. We will also sample the solar principal plane at 1deg angular resolution at 0.5 Hz sampling rate. With a total weight of 41 kg, the ASG is easily portable by an individual via sled.
Keywords: Instrumentation, Snow measurements, Snow properties

Modeling crop water use in the Pacific Northwest: The USBR AgriMet program - Palmer, P.L. (68th Annual Western Snow Conference, 2000)
Water supplies are limited in the arid western United States, and demands on water resources continue to grow. Environmental concerns for fish and wildlife, endangered species, and recreation call for reductions in consumptive use, leaving more water in rivers, lakes and streams. In many states in the west, irrigated agriculture accounts for an overwhelming majority of total consumptive water use. Recognizing the opportunity for water conservation in irrigated agriculture, the U.S. Bureau of Reclamation, in partnership with Bonneville Power Administration, began installing a network of agricultural weather stations in the Pacific Northwest in 1983. From an initial 3 stations, the network has grown to over 50 stations in Idaho, Oregon, Washington, and Montana. The network, called AgriMet (for Agricultural Meteorology), measures the weather parametersrequired to model crop evapotranspiration, or 'ET'. These data are telemetered by satellite to a receiving station in Boise, Idaho, where they are incorporated into the Kimberly-Penman ET equation. Each day during the growing season, crop water use charts are developed and disseminated via the World Wide Web and a dial-up computer system to irrigators and agricultural consultants in the Northwest By knowing the water holding capacity of the soil and the root depth of the crops, irrigators can use ET information to apply the right amount of water to their crops at the right time. Benefits of scientific irrigation scheduling include water conservation, reduced energy and fertilizer cost, reduced soil erosion, and protection of water quality by reducing runoff and groundwater infiltration of pesticide and fertilizer laden water.
Keywords: AgriMet, Evapotranspiration, Modeling

World class snowfall in the Sierra Nevada, 1969 - Powell, D.R. (68th Annual Western Snow Conference, 2000)
On a State of California snow survey in the Upper Kern River Basin in the Sierra Nevada, 366 cm (144 in, 12 ft) of snow fell in 48 hours, February 22-24, 1969, at the Big Whitney Meadow cabin, 3,048 m (10,000 ft) elevation. This was the maximum intensity snowstorm in my over 30 years experience of field snow surveying in the Sierra Nevada, Afghanistan, and Chile, and ranks with 48-hour totals recorded anywhere in the world.Some major results -constant shoveling of doorway and roof with my being buried in a slide off the roof, the difficulty of measuring the adjacent Big Whitney Meadow snow course after this massive accumulation, the extreme difficulty of ski travel through this new snow, the encounters with the United States Air Force planes searching for two lost fliers, the arrival at the car at the road-head to find the rear wheels stolen.
Keywords: Kern River Watershed, Record snowfall

The top ten Northern California floods of the 20th century - Roos, M. (68th Annual Western Snow Conference, 2000)
The purpose of this paper is to summarize the big northern California floods of the 20th century. These were all winter season general floods covering a large area. They are caused by a strong flow of moist subtropical air from the southwesterly direction. When the moist winds hit the mountain ranges, air is lifted, with copious amounts of rain extending to high elevations. The primary cause of high river runoff is simply too much rain, but melting of a prestorm snowpack can add to the runoff, perhaps up to 15 percent on major Sierra Nevada west slope rivers.The history of large floods show that these occur at sporadic intervals. The one in 1907 became the impetus and guide for building the Sacramento River flood control project with its bypass overflow system. Flood control storage behind large multipurpose dams in the foothills added to flood protection. The system design was taxed by the enormous New Years flood of 1997 which set many new records for flood peaks, flood volumes, and in areal extent. There seems to be a trend for increasing flood size in the latter half of the 20th century.
Keywords: California floods, Flood history, Winter floods, Flood Control, 1997 flood

Estimating snowpacks in a dynamic prairie environment - Steppuhn, H. (68th Annual Western Snow Conference, 2000)
The Northern Great Plains and the Canadian Prairies cover a vast area east of the North American Rocky Mountains. The climates of these plains and prairies exemplify the classic mountain rain-shadows at mid-Iatitudes with two dominant seasons: winter, and summer. Snow can blanket these lands at any time from September through June. The snowfall can accumulate on the ground forming snowpacks which vary widely in magnitude, areal coverage, and persistence from location to location and from year to year.Widely varying snowpack depths (d), water equivalents (WE), and areal covers (A) typify cold, windy, prairie environments on the North American plains and prairies. The wide range in seasonal snowpack accumulations stems from the region's size and dynamic weather. Extremes are expected almost every year but typically occur in different locations. Although accurate estimates of snowpack d, WE, and A serve for effective resource management, they are often difficult to obtain. A technique, based on stratification according to terrain and vegetation, utilizes precipitation gauge accumulations to estimate mean snowcover WE-values as the season progresses. Gauge accumulations are adjusted for evaporation and meltwater releases by incorporating com mon meteorological station measurements. A model of the technique applied to data from Saskatchewan, improved R2 values from 0.40 to 0.76 for regressions of precipitation gauge WEs with areal mean WEs measured in field snow surveys.
Keywords: Measurement techniques, Snow covered area, Snow measurements, Statistics

Predicting the 1.5-,5-, 10-, and 25-year event from the snow zone of Colorado and Wyoming - Troendle, C.A.; Porth, L.S. (68th Annual Western Snow Conference, 2000)
Scientists have been trying to develop equations to accurately predict streamflow for years. As of yet the most well known equations to do this were developed by the United States Geological Survey (USGS). This paper presents the results of our search to improve equations that predict the 1.5-, 5-, 10-, and 25-year maximum instantaneous flow and maximum mean daily flow for watersheds in the snow zones of Colorado and Wyoming. Using the same set of data utilized by the USGS, but with a more rigorous selection criteria, we have developed prediction equations that not only have a much smaller range of error, but these equations can be applied over a broader geographic area, rather than being restricted to specific Hydrologic Regions.
Keywords: Maximum daily flow, Peak flow, Recurrence interval

1999 Title, Contents, and Minutes (67th Annual Western Snow Conference, 1999)

Hydrologic computer simulation for the Upper Snake River reservoir system - Abramovich, R.; Ammon, R.; Coble, K.; Swank, L. (67th Annual Western Snow Conference, 1999)
A computer software program has been developed to visually simulate and display the daily operation of the Upper Snake River and Reservoir System in eastern Idaho and Wyoming. R*TIME, a real time software system developed by SCIENTECH Inc., has been linked to the water district's database creating a visual display of daily reservoir contents, river discharges, and snow water equivalent graphs and indexes while utilizing color alarms and river widths in proportion to flow. The real time display configuration provides the user and audience with a fast analysis and comparison of previous water years that was previously possible only with meticulous study of charts and graphs, or years of experience. The simulation display includes a time scale with pause, rewind, and fast , forward buttons enabling the users to animate the reservoir 'teacup' display at variable speeds. The computer simulation is used as a tool for improving future water management and distribution by policy makers, water resource managers and water users. It is also an educational tool for displaying the complexity of a river and reservoir system.
Keywords: Modeling, Real time, Reservoir discharge, Simulation

SNOTEL network - analysis of and future plans for the collection of additional climatic parameters at SNOTEL stations - Abramovich, R.; Pattee, S. (67th Annual Western Snow Conference, 1999)
Advancements in technology and sensor development have allowed additional climatic data to be collected in harshwinter environments associated with remote SNOTEL sites. The new generation of climatic data collectedincludes snow depth, wind speed and direction, solar radiation, humidity, soil moisture and soil temperature.Currently, several of these sensors are being evaluated in remote mountainous areas. The snow depth sensor isproving to be a reliable and dependable sensor and will produce a wealth of additional information such as dailysnowfall amounts, depth of snow on ground, and when combined with snow pillow data, snowpack density. Thispaper summarizes 1) the new generation of climatic data being collected and requested, 2) problems encountered3) products and studies utilizing the data, 4) quality control of data, and 5) future plans for installing these climaticsensors at SNOTEL sites.
Keywords: Climate data, Sensors, SNOTEL, Snow depth

Combining binary decision tree and geostatistical methods to estimate snow distribution in a mountain watershed - Balk, B.; Elder, K.; Winstrall, A.; Elder, K. (67th Annual Western Snow Conference, 1999)
We model the spatial distribution of snow across a mountain basin using an approach that combines binary decision tree and geostatistical techniques. In April 1997 and 1998, intensive snow surveys were conducted in the 6.9 km2 Loch Vale watershed (L VWS), Rocky Mountain National Park, Colorado. Binary decision trees were used to model the large-scale variations in snow depth while the small-scale variations were modeled through kriging interpolation methods. Binary decision trees related depth to the physically based independent variables of net solar radiation, elevation, slope and vegetation cover type. These decision tree models explained 54-65% of the observed variance in the depth measurements. The tree-based modeled depths were then subtracted from the measured depths, and the resulting residuals were spatially distributed across L VWS through kriging techniques. The kriged estimates of the residuals were added to the tree-based modeled depths to produce a combined depth model. The combined depth estimates explained 60-85% of the variance in the measured depths. Snow densities were mapped across L VWS using regression analysis. Snow-covered area (SCA) was determined from high- resolution aerial photographs. Combining the modeled depths and densities with a snow cover map produced estimates of the spatial distribution of snow water equivalence (SWE). This modeling approach offers improvement over previous methods of estimating SWE distribution in mountain basins.
Keywords: Modeling, Snow covered area, Snow distribution, Statistical methods

Predicting snowpack using the Southern Oscillation Index - Brewer, T.J. (67th Annual Western Snow Conference, 1999)
The El Nino-Southern Oscillation phenomenon is a known factor influencing the climate and streamflow patterns in the western United States. Previous studies have incorporated the Southern Oscillation Index (SOl) into statistically-based streamflow forecast procedures. This paper highlights some problems those studies have identified and discusses a new forecast procedure. Since the majority of the water supply in the Northwest starts as snow in the mountains during the winter months, snow water equivalent (SWE) is used as the dependent variable in this new non-statistical forecast procedure. This procedure uses the SOl to predict seasonal precipitation as measured by SWE at a designated site. The SOl data through June is used in mid-July to prepare a forecast of the October through December snow accumulation. Similarly, the SOl data through September is used in mid- October to prepare a forecast of the January through March snow accumulation. The procedure compares the changing SOl over time to historical SOl and SWE patterns. The results show that it is possible to predict future SWE for the Vienna Mine Snotel site in southern Idaho using current year SOl data. The forecast would be for 'near-average,''above near-average,' or 'below near-average' snow accumulation during the period.
Keywords: ENSO, Streamflow forecast, SWE, SOI, Vienna Mine SNOTEL

Spatial and temporal variations of bulk snow properties in an alpine/subalpine watershed, Rocky Mountain National Park - Clements, S.; Tonnessen, K.; Elder, K. (67th Annual Western Snow Conference, 1999)
Deposition of air pollutants to snowpacks is a concern to the health of aquatic and terrestrial ecosystems in Rocky Mountain National Park due to the possible acidic pulses of solutes during spring snowmelt. This studyestablished spatial and temporal patterns and variations in snow chemical concentrations related to snow distribution and spring melt patterns in the high elevation alpine/subalpine Loch Vale watershed (LVWS), and sought to determine if the snow chemistry reflects the observed differences in stream chemistry between Icy Brook and Andrews Creek.A snow survey conducted in 1996 sampled thirteen sites selected to represent the variability in slope, aspect, and elevation in the LVWS. Bulk snow chemistry samples and snow depth and snow water equivalence (SWE) measurements were taken during four sampling periods from April through June. The elution of ions from the snowpack did not follow the same pattern throughout the watershed. Snow depth, aspect, and location within the watershed accounts for some of the observed differences in stream chemistry .
Keywords: Air pollutants, Snow chemistry, Snow properties, Stream chemistry

Can satellite snow maps, ground measurements and modeling improve water management and control in the Kings River Basin, California? Efforts toward finding the answer - Davis, R.E.; Pangburn, T.; Daly, S.; Ochs, E.; Hardy, J.P.; Bryant, E.; Pugner, P. (67th Annual Western Snow Conference, 1999)
The U.S. Army Corps of Engineers has begun implementation of a new operational system for monitoring snow conditions, modeling changes to the snow, and routing snowmelt runoff through the stream and reservoir systemof a watershed. This system has as its basis four functional elements, including a graphical user interface for displaying, manipulating, and analyzing data; a system for mapping snow extent and water equivalent; a spatially distributed snow model, and a grid-based runoff routing model. The user interface links snow maps and model results, as well as Corps of Engineers and other agency databases. We use measurements from the Advanced Very High Resolution Radiometer (AVHRR) to make maps of snow extent represented as fractional extent per pixel. When merged with interpolations of ground-based measurements, these maps estimate the spatial distribution of water equivalent. A grid-based distributed snow model makes independent estimates of water equivalent and melting, which feeds the runoff routing model. The satellite-derived product will provide the basis for updating model results. Our demonstration area, the Kings River watershed, lies in the Sierra Nevada, California. This paper describes the functional elements and integration of these elements, the current status of the project, and future directions.
Keywords: Grid, Modeling, Routing, Snow covered area, Snow distribution

The effects of evapo-sublimation on the planning of precipitation and runoff augmentation programs - Dexter, L.R.; Avery, C.C.; Delinger, W.; Sayers, R. (67th Annual Western Snow Conference, 1999)
No abstract
Keywords: Forecasting, Snowpack, Snowpack augmentation, Sublimation

Measuring and monitoring snow depth using the global positioning system - Elder, K.; Gray, M.; Major, P.; Nyberg, C. (67th Annual Western Snow Conference, 1999)
Ski resorts need to monitor snow depth over their slopes from the start of the accumulation or snowmaking season until spring closure. There is currently no system available that provides real-time, high-resolution, high-frequency data for mapping snow over space on an operational basis. Air- and space-borne sensors either lack the spatial resolution or temporal frequency necessary for daily ski resort operations. In addition, inclement weather reduces the capabilities of sensors in the visible portion of the spectrum. We evaluated the potential of the Global Positioning System (GPS) to meet the operational needs. We used post processed kinematic GPS equipment for a static survey over a fixed transect to find the capabilities of the system to detect changes in the elevation of the snow surface through time and over space. The GPS equipment was also mounted on over-snow vehicles to determine the effect of vehicle movement on GPS accuracy. Our results suggest that GPS equipment should allow ski resorts to measure snow depth well within the study design constraints of 0.15 m.
Keywords: GPS, Snow depths

Equivalent permeability of a continental, alpine snowpack - Fox, A.M.; Williams, M.W. (67th Annual Western Snow Conference, 1999)
Most snowpacks are not homogeneous, but consist of a number of snow and ice layers with varying permeabilities. In such cases, an 'equivalent' permeability can be used as an integrated or bulk property of the entire snowpack depth and is a useful parameter for gravity-flow and numerical models of meltwater flow through isothermal snowpacks. Calculated surface meltwater flux and Iysimeter discharge were used to establish daily relationships between specific meltwater fluxes and wavespeeds through the snowpack at a continental, alpine site in 1996 and 1997. These relationships were used to determine a pore-size distribution index (E) and to calculate equivalent permeability. Values for E were found to vary considerably and could not be related to other measured snowpack properties. Values were in the lower range of those previously reported, often less than 3, and were highly dependent on the range of meltwater fluxes used in calculations. Equivalent permeability was also at the lower limit of values reported in the literature, and varied by 2 orders of magnitude from 1.08 x 10 to the 11th to 2.79 x 10 to the 8th m2. In 1997 it declined considerably over 16 days.
Keywords: Lysimeters, Meltwater flow, Snowpack permeability

Runoff forecast error uncertainty and some ways it can affect snowmelt water scheduling decisions in the Sierra - Freeman, G.J. (67th Annual Western Snow Conference, 1999)
Forecasting runoff and scheduling reservoir releases for PG&E's hydroelectric system, located in California's Sierra and Southern Cascade Watersheds, requires that watersheds be subdivided into subbasin reaches between diversion dams to facilitate computation of daily unimpaired sidewater inflow for each subbasin reach. Computation of daily unimpaired subbasin sidewater flow allows hydro schedulers to construct a feasible operation plan that optimizes water releases from upstream reservoirs for purpose of maximizing hydroelectric value while satisfying multiple constraints such as are often imposed for instream flows, whitewater rafting, planned maintenance, and recreation. What occurs with subbasin daily flow computation is large variance among successive daily flows. This variance is seldom explainable by hydrologic events alone. However an explanation can be found, when one reviews propagation of error uncertainty and daily storage change taking place at upstream reservoirs. In addition the April through July seasonal runoff forecast has a tendency to carry the full standard error of the estimate forward into the final ablation phases of snowmelt. At that point, the relative magnitude of the error compared with remaining flow yet to come causes large error uncertainty that often affects optimal final seasonal filling of reservoirs.
Keywords: Forecasting, Optimization, Reservoir operation, Snowmelt

Topographical mass balance determination of Teton Glacier, Wyoming - Gray, M.; Elder, K.; Tonnessen, K.; Ramirez, J.; Laituri, M.; Greenwood, R. (67th Annual Western Snow Conference, 1999)
The presence of glaciers affects stream discharge because they store precipitation and influence the timing of runoff. Aglacier's influence is attributed at least in part to its change in mass. Mass balance, a calculation of the glacier's change in mass over a period of time, has been estimated in this study by volumetric changes assessed from surface fluctuations assuming constant density. Our analysis used topographic surveys performed in 1954,1963, and 1994 ofTeton Glacier, Wyoming. The surveys were used to create representative surfaces that were quantitatively compared using geographic information system (GIS) tools. Calculations performed indicate an average decrease of 26,000 m3/yr from 1954 to 1994.
Keywords: GIS, Glaciers, Mass balance

Snowmelt contributions to flooding in the Lake Tahoe Basin - Kattelmann, R.C. (67th Annual Western Snow Conference, 1999)
Lake Tahoe receives national attention for its declining water quality and the massive public investments in attempts to halt and reverse that decline. Much of the nutrient and pollutant load is delivered to the lake during large runoff events. This paper attempts to contribute to the understanding of those larger events by describing the flood history from the record of gaged tributaries to the lake and the mechanisms of large-flow generation in the Lake Tahoe basin. Although snowmelt runoff every spring produces significant flows of long duration, the mid-winter rain-on-snow events cause the highest peaks. Because the lower extent of the tributary catchments is the lake at an elevation of about 1900 m, only the warmest storms produce substantial rainfall in the basin. Nevertheless, some of these storms have generated massive amounts of runoff and sediment. In most cases, the snow cover influenced the release of water to streams without adding much volume from melt. However, there were a few notable exceptions with significant snowmelt.
Keywords: Snowmelt, Spring runoff, Warm storms

Fallen Leaf Lake: A microcosm of Lake Tahoe - Kleppe, J.A.; Norris, W.J. (67th Annual Western Snow Conference, 1999)
This paper presents an overview of the reasons that Fallen Leaf Lake has been proposed as a microcosm of Lake Tahoe. It is postulated that the problems being faced in the Lake Tahoe Basin are social, political, economic and finally, scientific in nature. These problems are exactly the same as those being faced by Fallen Leaf Lake. Fallen Leaf Lake is shown to offer a unique opportunity to develop concepts, methods, instrumentation, monitoring approaches and complex models that will be essential to developing a long term management plan for the Lake Tahoe Basin. Air quality , water quality, aquatic systems, as well as a multitude of other complex issues can be readily studied on a smaller lake such as Fallen Leaf. The dynamics of Fallen Leafs ecosystems are quite responsive due to its small size and offers a 'real world' working modelto develop answers for the problems found in the Lake Tahoe Basin. For purposes of this paper a focus is made on the hydrological aspects of the microcosm and the development of new sensor- technology that can be extrapolated to the entire Lake Tahoe Basin.The 'bottom line' conclusion is this -if problems cannot be solved on the scale of the smaller more manageable Fallen leaf Lake, it is then highly unlikely they can be solved for the much larger Lake Tahoe.
Keywords: Microcosm, Political problems, Social problems

GIS tool to cpmpare simulated and remotely sensed snow-cover observations - Koczot, K.M.; Dettinger, M.D. (67th Annual Western Snow Conference, 1999)
A GIS (geographic information system)-based Snow-Cover Comparison Tool (SCCT) is being developed for useby watershed modelers and other analysts to make comparisons between simulated and remotely sensed snow cover. In the past, watershed-model simulations have been calibrated almost entirely by comparison of simulated with observed streamflow variations. Watershed-model calibrations can be improved by verifying that snowpack distributions and conditions within the basin are simulated accurately, but this requires careful registration of observations to model land units. The SCCT facilitates these additional comparisons. NOAA' s satellite-based snow-cover images on 1,101 meter grid cells are compared here with simulations, on 100-meter grid cells, of snowpacks in the Merced, American, and Carson Rivers of the Sierra Nevada on selected dates. Statistical analyses of disagreements between observed and simulated snow cover show a strong dependence of model error on altitude. Comparison maps, produced by the SCCT, make the spatial distributions of these errors easy to visualize.
Keywords: Calibrations, GIS, Modeling

Lake Tahoe: Microcosm of environmental history - Mergen, B. (67th Annual Western Snow Conference, 1999)
Lake Tahoe can be seen as both a microcosm and a symbol of the American environmental movement. From John C. Fremont's tantalizing glimpse through the mist of a February morning in 1844 to the well-publicized presidential summit in 1997, the Lake has been described as sublime and squalid, enchanting and endangered, resource and resort, wilderness utopia and urban wilderness. As the environmental movement has evolved from preservation to conservation to sustainability to 'deep ecology,' debates about Lake Tahoe have mirrored these frequently conflicting philosophies. This paper illustrates the principal issues in environmental history with examples from Lake Tahoe. I also argue that water clarity as a symbol for the total environment complicates decision-making and management.
Keywords: Environmental management

Precipitation intensity during rain-on-snow - Osterhuber, R.J. (67th Annual Western Snow Conference, 1999)
Mid-winter rainfall onto established snowpacks has the potential to generate high stream flows and flooding. Rain-on-snow can also increase the potential for snow avalanche. Precipitation intensity is a vital piece ofinformation when forecasting and assessing stream flow and snow stability during rain-on-snow. Precipitation intensity during 120 rain-on-snow storms from the past 21 winters at the Central Sierra Snow Laboratory in the Sierra Nevada of California were analyzed. These data were used to generate both storm and seasonal recurrence intervals for varying mid-winter rainfall intensities. Mid-winter rainfall intensities were found to range between less than 1 mm/hr to over 27 mm/hr with a mean of 2 mm/hr. Mean maximum rainfall intensity was found to be 5 mm/hr for approximately 5 hours. An average annual maximum rainfall rate of 8 mm/hr has a recurrence interval of approximately 3 years.
Keywords: Flooding, Forecasting, Rain-on-snow, Snow stability

Comparison of water quality for upstream and downstream sites in the Incline Creek Watershed, Lake Tahoe Basin, Nevada, 1990-98 - Rowe, T.G. (67th Annual Western Snow Conference, 1999)
The U.S. Geological Survey, and the Tahoe Research Group, in cooperation with the Tahoe Regional Planning Agency, has monitored tributaries in the Lake Tahoe Basin since 1987. Monitoring is to determine streamflow and concentrations of sediment and nutrients to Lake Tahoe. In 1989, the monitoring network was expanded to support the assessment of the effects of land use and development on water quality in the basin. Data from one watershed, Incline Creek, are described for the 1990-98 water years.The median values of instantaneous streamflow, specific conductance, suspended sediment, and bioreactive iron all increased in a downstream direction. Median streamflow increased from 3.1 to 8.2 ft3/S (cubic feet per second) and median specific conductance increased from 35 to 78 uS/cm (microsiemens per centimeter) at 25deg C (degrees Celsius). Also in a downstream direction, median suspended sediment increased from 7 to 24 mg/L (milligrams per liter) and median bioreactive iron increased from 242 to 972 ug/L (micrograms per liter).The median values of total Kjeldahl nitrogen and total phosphorus increased slightly in a downstream direction. Median total KjeldahI nitrogen increased from 0.160 to 0.206 mg/L and median total phosphorus from 0.036 to 0.055 mg/L. The median values of water temperature, pH, and concentrations of dissolved oxygen, dissolved nitrite plus nitrate, dissolved ammonia, and dissolved orthophosphorus showed virtually no trends with distance downstream.
Keywords: Monitoring network, Nutrients, Sediments, Water quality

Predicting the effect of a forest canopy on ground snowpack accumulation and ablation in maritime climates - Storck, P.; Lettenmaier, D.P. (67th Annual Western Snow Conference, 1999)
To investigate the processes controlling snow accumulation and ablation beneath forest canopies in maritime climates, continuous measurements of snow water equivalent (SWE) and snowpack outflow were made during the winters of 1996/97 and 1997/98 at a site in the transient snow zone of the Southern Oregon Cascades. Measurements were taken with large weighing Iysimeters (-25 m2) below a mature canopy and in an adjacent harvested site. Analysis of the observations shows that approximately 60% of annual snowfall was intercepted by the canopy (up to an apparent maximum above 30 mm), with approximately 72 percent removed as meltwater drip and 28 percent removed as large snow masses. Apparent sublimation rates from the intercepted snow were less than 1 mm per day. These data, along with measurements of standard micrometeorology , were used to develop and test an energy balance model of snow interception and canopy effects on ground snowpack ablation. The model represents intercepted snow load as a function of Leaf Area Index, adjusted for the effects of temperature. Removal of intercepted snow by sublimation, melt -water drip and mass release is governed by available energy , the vapor pressure deficit, and the liquid water content of the intercepted snow. The profiles of wind and radiation through the canopy are modeled explicitly. Turbulent heat exchange at the surface is calculated via the bulk aerodynamic method and corrected for atmospheric stability via a modified Richardson's number approach. The model was calibrated to the 1996/97 observations and validated using the 1997/98 data. Model predictions of snow accumulation at both sites are highly sensitive to the rain/snow threshold temperature while predicted ablation agrees well with observations.
Keywords: Ablation, Accumulation, Forest canopy, Lysimeters, Oregon Cascades

Implementation of digital terrain analysis to capture the effects of wind redistribution in spatial snow modeling - Winstrall, A.; Elder, K.; Davis, R.E. (67th Annual Western Snow Conference, 1999)
Though the effects ofwind-induced snow redistribution in mountainous locales are readily observed, the complexity of wind fields over rugged terrain has stymied attempts to model snow transport in these regions. The accuracy of spatial snow models that have been unable to include redistribution effects has been thusly compromised. This research designs, develops, and evaluates parameters that numerically represent terrain features that affect the degree of exposure to prevailing winds at each cell within a grid. The study area is the windswept 8.1-km2 Green Lakes Valley watershed along the Colorado Front Range. Comparisons are made among parameters representative of surface curvature, average upwind fetch, average upwind horizon, and average upwind slope gradient. All of these representative parameters are significant predictors of snow distribution representative of a process at least as important as radiation input in determining peak snow accumulations. Additionally, a slope divergence parameter is shown to successfully delineate regions prone to heightened accumulations in lee slope eddy zones. Ultimately it is demonstrated that the inclusion of a wind redistribution factor within a regression tree model produces a more accurate and very different spatial model of snow distribution compared to a model that does not include an eolian influence.
Keywords: Digital Terrain Modeling, Model, Snow distribution, Wind effects

1998 Title, Contents, and Minutes (66th Annual Western Snow Conference, 1998)

Long-range snowpack forecasting based on North Pacific Ocean sea surface temperatures - Ames, D.P. (66th Annual Western Snow Conference, 1998)
Correlation analysis is used to establish the connection between interannual variations in the historical snowpack record from Paradise Ranger Station on Mount Rainier in Washington State and leading climatic indicators of the Pacific Ocean. Additionally, connections between historical gridded monthly sea surface temperature data from the Pacific Ocean and the snowpack record are explored in an effort to establish a basis for qualitative long range snowpack prediction.
Keywords: Mount Ranier, Ocean curents, Ocean temperature

Does El niño affect snowpack in Utah - Baldwin, C.K. (66th Annual Western Snow Conference, 1998)
Nine snow gauging stations in Utah are analyzed to detennine the impact of El Nino on snowpack (snow water equivalent) across the state. The stations were chosen based primarily on the length of record. The effect of latitudinal variation as well as temporal variation on El Nino impact is considered. The importance of the stationary atmospheric wave pattern in the N. hemisphere during El Nino events is demonstrated. The Pacific North American (PNA) pattern provides a convenient and effective measure of the state of the atmospheric wave pattern that impacts Utah. A response table showing the impact of various combinations of El Nino and the PNA pattern shows that significant impacts on snowpack occur when both the El Nino and PNA indices are at extreme values. Correlation analysis reveals that N. Utah is negatively correlated with El Nino, while S. Utah is positively correlated with El niño, with the transition between these two extremes being nearly linear. A forecast based on the results is presented, which indicates that the next two years will be near-normal.
Keywords: El niño, Ocean currents, Ocean temperatures

Using geostatistical methods to estimate snow water equivalence distribution in a mountain watershed - Balk, B.; Elder, K.; Baron, J. (66th Annual Western Snow Conference, 1998)
Knowledge of the spatial distribution of snow water equivalence (SWE) is necessary to adequately forecastthe volume and timing of snowmelt runoff. In April 1997, peak accumulation snow depth and density measurements were independently taken in the Loch Vale watershed (6.6 km2), Rocky Mountain National Park, Colorado. Geostatistics and classical statistics were used to estimate SWE distribution across the watershed. Snow depths were spatially distributed across the watershed through kriging interpolation methods which provide unbiased estimates that have minimum variances. Snow densities were spatially modeled through regression analysis. Combining the modeled depth and density with snow-covered area (SCA) produced an estimate of the spatial distribution of SWE. The kriged estimates of snow depth explained 37-68% of the observed variance in the measured depths. Steep slopes, variably strong winds, and complex energy balance in the watershed contribute to a large degree of heterogeneity in snow depth.
Keywords: Snow accumulation, Snow covered area, Snow density, Snow depth, Statistical analysis

GIS assessment of GCM forecasts of upper air circulation and expected impacts on winter precipitation in Western North America - Berg, A.A.; Byrne, J.M.; Townshend, I.J. (66th Annual Western Snow Conference, 1998)
This study assesses the impact of global warming on northern Rocky Mountain States April 1 snowpack as influenced by 50 kPa synoptic fields for lx and 2x CO2 warming scenarios generated by the CCC GCM-II. The synoptic pattern observed was subjectively classified into one of seven 50-kPa winter time synoptic patterns that explained almost ninety percent of the non-average annual snowpack patterns in the study area. Two analysis were completed: fIrst to compare the 1 xCO2 predictions of synoptic type frequency to historical data, and secondly to compare lxCO2 predictions to the 2xCO2 simulation. The lxCO2 run of the GCM was found to statistically simulate the historical patterns well for all but one of the seven synoptic patterns. Comparison of the 2x and lx run of GCM indicates a statistically significant increase in a synoptic pattern associated with wet conditions in the north of the study region and dry conditions in the south, and a decreased frequency of patterns resulting in dry conditions in northern regions and relatively wet conditions in the south. From this analysis is expected that the decrease in mid-latitude jet occurrence over the southern regions of the study area could result in lower snowpack conditions over this region in a warmed scenario.
Keywords: Carbon dioxide, Climate change, Climate change models, Global warming, Impacts

Using GIS to establish relationships between environmental variables and snowdepths in Green Lakes Valley, Colorado, for use in SWE estimations and forecasting - Brown, S.M.; Williams, M.K. (66th Annual Western Snow Conference, 1998)
Geographic Infonnation Systems (GIS) may be useful in forecasting the quantity ofwater stored in alpine snowpacks because relationships may be established between environmental characteristics and seasonal snowdepth patterns for watersheds of interest. A snow survey perfonned in May of 1997 for the 224-ha Green Lake 4 Watershed of the Colorado Front Range involved intensive sampling (n = 194) of snowdepth and snow density measurements around the basin. These field data, in conjunction with snow covered area, DEM and landcover data from the Niwot Ridge LTER Spatial Database, were used to investigate 1) the relationship of snowdepth to landcover, 2) the relationship of snowdepth to slope, and 3) the relationship of snowdepth to aspect.
Keywords: Forecasting, GIS, Niwot Ridge

Snow water equivalents modeled at the mesoscale with geographical information systems - Carey, J.; Decker, R. (66th Annual Western Snow Conference, 1998)
Snow water equivalent (SWE) is spatially distributed within the mountainous basins of climates marked by a seasonal snowpack. This distribution is directly linked to mesoscale physiography such as slope, solar aspect, elevation, canopy, wind transport zones and avalanche tracks, and to time. In the Oquirrh Mountains near Salt Lake City, the SWE distribution of seven subbasins has been modeled with GIS technology and a DEM of the area. The purpose of the model is to obtain accurate estimates of SWE for smaller basins. The modeled subbasins are on the order of 1 km2.Individual maps of mesoscale physiography were developed as the controls of SWE distribution. Daily, water year 1997 data from three SnoTel stations was compared with physiographic maps. Using snow accumulation theory and a statistical analysis of ground measured data, individual SWEdistribution models were fit with the mesoscale models of solar aspect, elevation, vegetation and basin area. The SWE distribution models, representing either loss or gain, were then combined in chronological order to model total snow accumulation for a season. Peak SWE was calculated for March 7, 1997 using the mesoscale accumulation model. A total SWE of 1882.74 acre-feet, 35.6% of average Bingham Canyon annual precipitation, was calculated for peak. Modeled site locations had a very good linear correlation (0.97) with measured site data. A ridge line cornice model contributed 51.99 acre-feet SWE, 2.7% of peak. The Snow Estimation and Updating System (SEUS) is implemented by the Colorado Basin River Forecast Center for macroscale SWE calculations. SEUS modeled 3569.35 acre-feet, 190% of the mesoscale model, for the same area and period. This study shows that the scale of the study area determines the influence of the mesoscale distribution on basin wide SWE determination.
Keywords: GIS, Modeling, SEUS

The UtahMesonet: Monitoring weather conditions over the intermountain west - Horel, J.; Slemmer, J.; McDonald, B.; Dunn, L.; Zaff, D. (66th Annual Western Snow Conference, 1998)
The Utah Mesonet has been under development during the past several years. The Mesonet has been designed tohelp forecasters in the Intermountain West obtain current weather conditions in a timely fashion. All available surface reports from manned and automated stations are collected, archived, and displayed at 15-minute intervals. While attention is focussed on meteorological parameters such as temperature and wind, precipitation information is also obtained from sensors installed by the National Weather Service near the Wasatch Mountains as well as information from Snow Telemetry (SNOTEL) sites and data collected by the Colorado River Basin Forecast Center.Operational and experimental forecasts of precipitation during January-May 1997 are evaluated over the western United States. The sensitivity of model forecast skill as a function of model horizontal resolution is assessed. Models that resolve the underlying terrain in greater detail (such as the 10 kIn and 29 kIn versions of the Eta model developed at the National Centers for Environmental Prediction) provide better forecasts of orographic precipitation during winter.
Keywords: SNOTEL, Weather network, Wind data

Rocky Mountain snowpack chemistry relative to El niño effects of water years 1993-97 - Ingersoll, G. P. (66th Annual Western Snow Conference, 1998)
Snowmelt-dominated runoff is correlated with El Nino-related Southern Oscillation Index events in the Rocky Mountain region. Generally. during El Nino winters, the Rocky Mountains are drier in the north and wetter in the south. Annual snow sampling by the U.S. Geological Survey during water years 1993-97 at 52 sites throughout the Rocky Mountain region near a variety of regional anthropogenic emissions sources revealed strong inverse relations between snow depth and chemical concentrations in the snowpack. The Southern Oscillation Index (SOl) indicates that 1995 was the strongest El Nino year affecting the Rocky Mountains during water years 1993-97. However, neither greater snowfall amounts nor correspondingly lower snowpack concentrations of ammonium, nitrate, or sulfate occurred that year. During water year 1997, the year with the least negative SOl and the weakest El Nino effect, the greatest variance in snow depths among the study sites was observed (p<0.005) relative to the other 4 years. Snow depths as a group in water year 1997 were significantly greater (p<O.06) than any other year (1993-96) with numerous record depths. Variance in snowpack chemistry among sampling years relative to water year 1995 correlates poorly to expected effects of El Nino. Differences in snow depths or snowpack chemistry have not occurred contemporaneously with El niño events, indicating that recent El Nino years may have little effect on snowpack chemistry in the Rocky Mountains.
Keywords: El niño, Snowpack chemistry, Southern Oscillation Index

The Franklin Basin problem - Julander, Randall P.; Wilson, G.R.; Nault, R. (66th Annual Western Snow Conference, 1998)
The Franklin Basin SNOTEL site displayed very curious and conflicting data during the winter of 96-97. Pillow data were far too high and various means and tests were undertaken to determine the cause and extent. The more data gathered, the more confusing reality seemed to become. The eventualconclusion was that a combination of snow creep and additional water from rain on snow events which formed an ice layer on the pillow resulted in the pillow overweigh.
Keywords: Ice layer, Rain on snow, SNOTEL

Maximum snowmelt rates: some observations - Kattelmann, R.C.; Cooley, K.R.; Palmer, P.L. (66th Annual Western Snow Conference, 1998)
In response to discussion and debate about how fast snow can melt under extreme conditions, this paper identifies and interprets some reported observations of rapid snowmelt rates. Energy availability suggests that maximum snowmelt under typical conditions in the mountains of North America is about 50 mm per day. Conditions that enhance snowmelt rates include long day-length near the summer solstice, clear skies during daytime combined with cloud cover at night, warm and humid air combined with high wind speeds, particulate matter in the near-surface snow layer, and discontinuous snow cover that is thin enough for sunlight to penetrate to the ground surface. Records of snowmelt rates from four research sites and more than ninety SNOTEL sites provide the observational basis to discuss empirical estimates of maximum melt water generation.
Keywords: SNOTEL, Snowmelt

Effects of el niño and la niña events on precipitation, temperature, and natural runoff volumes in Alberta, Canada - Keller, R. (66th Annual Western Snow Conference, 1998)
Precipitation, temperature and natural runoff volumes over the province of Alberta, Canada were associated with the two extreme phases of Southern Oscillation, namely El Nino and La Nina. Spatial and temporal data were analyzed for the 1911-1995 period for the first winter following the onset of the El Nino and La Nina cycles in Alberta. The strongest signal for El Nino and La Nina appeared in the December to February period following their onset with some signal apparent in the November to March period. This paper includes a general description of the climate processes involved and the results for the December to February period following the onset of El Niño and La Nina events. The analyses include 22 El Nino and 14 La Nina events that occurred in the study period with an update on the current 1997-98 El Nino event. The results for the December to February (winter) period following the onset of El Nino show statistically significant above-average temperatures in all areas of Alberta. Decreased winter precipitation was evident at all stations following the onset of El Nino, however differences were very small at most locations. Natural runoff volume (computed for the February to July period) on average, provided below-average values following El Nino winters.Conversely, significant below-average temperatures were found in Alberta for the winter following the onset of a La Nina event. La Nina events provided significantly above-average precipitation at all sites and subsequently, above-average natural runoff volumes were found.
Keywords: El niño, La niña, Precipitation, Runoff, Temperatures

A spatially distributed energy balance snowmelt model for application in mountain basins - Marks, D.; Domingo, J.; Susong, D.; Garen, D.C. (66th Annual Western Snow Conference, 1998)
Snowmelt is the principal source for soil moisture, ground-water recharge, and stream-flow in mountainous regions of the western U.S. Information on the timing, magnitude, and contributing area of melt under variable or changing climate conditions is required for successful water and resource management. A coupled energy and mass-balance model was used to simulate the development and melting of the seasonal snowcover in several mountain basins in California, Idaho, and Utah. Simulations were done over basins varying from 1 to 10,000 km2, with simulation periods varying from a few weeks for the smallest basin, to multiple snow seasons for the larger basins. The model, ISNOBAL, is a spatially distributed form of the model SNOBAL, which was described in great detail by Marks, et al. (1998).
Keywords: Energy balance, ISNOBAL, Mass balance, Modeling, SNOBAL

Spatially distributed snow modeling and hydrograph simulation -- Continuing Boise River application - Moore, D.S.; Garen, D.C. (66th Annual Western Snow Conference, 1998)
Progress is reported for an ongoing project to apply a snow model coupled with a hydrograph simulation model, both spatially distributed, to a river basin of extensively managed water resources. Snowpack, precipitation, and temperature have been monitored in the Boise River Basin of Idaho for years by both the Natural Resources Conservation Service (NRCS) and the Bureau of Reclamation. In this latest phase of the project, additional sensors have been installed at three NRCS SNOTEL sites, which are expected to improve the snowpack simulation. How these new data are applied in the model will be discussed, as well as the direction of further work.
Keywords: Basin management, Modeling, SNOTEL

El Niño/Southern oscillation signals in the long term climate of Donner Summit, California - Osterhuber, R.J. (66th Annual Western Snow Conference, 1998)
The latest El Nino event has prompted questions about the predictability of North American weather based on therelative strength of the Southern Oscillation Index (SOl). The annual precipitation, snowfall, and air temperature data from an area near Donner Pass, California have been analyzed in comparison with the SOI from the equatorial Pacific Ocean. There was found to be a positive correlation between decreasing SOl values and increasing annual precipitation; a positive correlation between increasing SOl values and increasing annual snowfall; and a positive correlation between increasing SOl values and increasing average annual air temperature. All these correlations, however, are weak. 64 % of the wettest years on record occurred with alow SOl, and 52% of the driest years on record occurred with a high SOl. Data was available from 1900 through 1997 excluding 1907, 1908, 1914, 1915, and 1932.
Keywords: El Niño, Ocean surface temperature, SOI

Snowpack snow water equivalent measurement using the attenuation of cosmic gamma radiation - Osterhuber, R.J.; Gehrke, F.; Condreva, K. (66th Annual Western Snow Conference, 1998)
Incoming, background cosmic radiation constantly fluxes through the earth's atmosphere. The high energy gamma portion of this radiation penetrates many terrestrial objects, including the winter snowpack. The attenuation of this radiation is exponentially related to the mass of the medium through which it penetrates. For the past three winters, a device measuring cosmic gamma radiation --and its attenuation through snow --has been installed at the Central Sierra Snow Laboratory , near Donner Pass, California. This gamma detector, measuring energy levels between 5 and 15 MeV, has proved to be an accurate, reliable, non-invasive, non-mechanical instrument with which to measure the total snow water equivalent of a snowpack. This paper analyzes three winters' worth of data and discusses the physics and practical application of the detector for the collection of snow water equivalent data from a remote location.
Keywords: Attenuation, Gamma radiation, Snow measurement

Local scale variability in storm snowfall and seasonal snowpack distributions in the Bridger Range, Montana - Pipp, M.J.; Locke, W.W. (66th Annual Western Snow Conference, 1998)
Synoptic and regional estimation of snow water equivalent often uses a sparse network of elevation-stratified snow measurements. The interpolation of such data on meso- and local scales has seldom been tested. Individual storms and April 1st snowpack were measured during the 1994-95 winter near Bozeman. Montana to assess geographic and meteorologic factors influencing meso- and local scale snowfall and snowpack distribution and its variability. A network of eleven measurement sites was established east of Ross Pass in the central Bridger Range. Results showed that the regional April 1st snow-elevation gradient predicts local scale gradients but a local scale gradient did not predict the regional scale. For storm distributions, elevation was significantly correlated in 50% of storms. Distance east of the ridge was significant in 81% of storms, and was more strongly correlated in six of the eight storms where elevation was also significant. However, because of strong covariance, partitioning these two signals was not possible and thus, either variable is a reasonable linear predictor of snow distributions in this study. Snowfall distributions were classified using hierarchical cluster analysis which identified four storm classes. Snow distributions in the Ross Pass area resemble distributions generated by small-scale barrier models.
Keywords: Elevation effects, Snow distribution, Snow measurements

Modeling snowdrift distribution in a small mountain watershed: Spatial and temporal scale limitations - Sommerfeld, R.L.; Smith, J.L. (66th Annual Western Snow Conference, 1998)
A model of total yearly accumulation using daily degree days and monthly snow covered areas from aerial photoswas tested against a 25 m gridded probe survey for the years 1990, 1992, and 1993. Agreement of the model with the survey was within ± 5% which is the estimated accuracy of the probe surveys. The snow depth distribution for the survey years was modeled by assigning depth contour values, derived from the degree day model, to the edges of the snow drifts delineated on the aerial photos. The rational was simply that shallower snow had melted away and deeper snow remained. The correlation between the modeled snow distribution and the probe survey was very good down to a resolution of approximately 1 hectare when the correlation became poor. The poor correlation at finer resolutions was attributed to the coarse spatial resolution of the 25 m probe survey and the coarse time resolution of the monthly aerial photos.
Keywords: Glacier Lakes Ecosystem Site, Modeling snow distribution, Snow depths

Managing snow to abate salinity - Steppuhn, H.; Miller, M. (66th Annual Western Snow Conference, 1998)
Food crops do not grow well in saline soils. Even relatively low concentrations of excess calcium, sodium and other salts dissolved in soil solutions reduce the grain yields of spring wheat, and other crops, by 5, 10, 20 percent or more. In arid or semiarid climates, ground water which approaches the soil surface typically leads to root-zone salinization. Subsurface drainage in these climates can usually lower the water table, but subsequent leaching of the offending salts out of the root zones often requires additional surface water to complement the natural precipitation. In many arid farming districts, irrigation provides this leaching water. Unfortunately, salinityaffects some 30 million hectares of semiarid, North American farmland for which irrigation waters are not available. Fortunately, many of these dryland farms exist in locations blessed with snowfall and wind. In this study, single rows of perennial grass, sown as windbreaks on 15-meter centers across drained saline fields, capture blowing snow and supply meltwater for leaching the root zones just before spring seeding. The mean salinity of saturated soil paste extracts obtained from sets of soil samples taken every fall from such a site in southwestern Saskatchewan averaged 14.1 dS/m during 1985-90 before the drainage was installed, 13.0 dS/m for 1991-92 before the grass windbreaks became established, and 9.4 for 1993-96 with both drainage and snow management.
Keywords: Prairie snow management, Salinity, Wheat

Near-surface faceted crystals and their effect on snow stability, Red Mountain Pass Corridor, Colorado - Stock, J.; Elder, K.; Birkeland, K. (66th Annual Western Snow Conference, 1998)
Avalanches may be important hydrologically if avalanche deposits alter the timing and volume of runoff. Avalanches often fail from a weak layer such as surface hoar. graupel. or faceted crystals. One important type of faceted crystal. called near-surface faceted crystals. form in the near-surface layers. During the 1997/98 winter. A study of near-surface faceted crystals was conducted along the Red Mountain Pass corridor, Colorado. Six types of near-surface faceted crystals were differentiated: small faceted crystals, radiation recrystallization grains. Faceted precipitation crystals, near-surface hoar, faceted partly-decomposed precipitation crystals and needles. A particularly well-developed near-surface facet layer that evolved in December acted as the dominant weak layer in the study area for seven weeks. Observation of 14 avalanches showed that 79% of the failures occurred on near-surface faceted layers. The majority of stability test failures occurred on near-surface faceted layers. Understanding the growth of near-surface faceted crystals and their effect on snow stability is important for avalanche forecasting.
Keywords: Avalanche forecasting, Snow crystals

Developing time-series climate surfaces to drive topographically distributed energy- and water-balance models - Susong, D.; Marks, D.; Link, T.; Garen, D.C. (66th Annual Western Snow Conference, 1998)
Topographically distributed energy- and water-balance models can accurately simulate both the development and melting of a seasonal snowcover in mountain basins. The models require time-series climate surfaces of air temperature, humidity, wind, precipitation, and solar and thermal radiation. If data are available, these parameters can be adequately estimated at time steps of 1 to 3 hours. Unfortunately, climate monitoring in mountain basins is very limited, and the full range of elevations and exposures that affect climate conditions, snow deposition, and snowmelt is seldom sampled. However, detailed time-series climate surfaces have been successfully developed using limited data and relatively simple methods. A synopsis of the tools and methods used to combine limited data with simple is presented.
Keywords: Hydrologic modeling, Modeling, SNOTEL, Time series

The Coon Creek water yield augmentation pilot project - Troendle, C.A.; Wilcox, M.S.; Bevenger, G.S. (66th Annual Western Snow Conference, 1998)
The Coon Creek pilot project represents an attempt to verify that water yield augmentation technology, demonstrated to work on small-scale experimental watersheds, could be applied at an operational or landscape scale with similar results. Coon Creek, a 1673 ha (4133 a) catchment on the East Fork of the Encampment River was selected as the treatment watershed and Upper East Fork, an adjacent catchment, was selected as the control. Following an adequate calibration period, road building and timber harvest disturbed a total of 23.7 percent of the watershed area. Seasonal streamflow (April-October) significantly increased an average of 71 mm (2.8 in) for the first 3 years after harvest. Peak flows, expressed as either instantaneous maximum flow or as maximum mean daily flow, were not significantly increased although the duration of the higher, near bankful, discharges were extended. The findings at Coon Creek support and are comparable with documented observations on smaller experimental watershed studies in the snow zone.
Keywords: Coon Creek, Forest management, Operational scale, Snowpack augmentation, Watershed management

Sensitivity of non-parametric trend analyses to multi-year extremes - Wahl, K.L. (66th Annual Western Snow Conference, 1998)
Non-parametric tests for trend are widely used in analyzing hydrologic data because they presume nothing about the underlying distribution and are relatively insensitive to the presence of individual outliers. However, hydrologic data often include multi-year sequences of wetter or drier than normal periods. Such sequences may be episodic in nature and may persist for several years, but may imply no systematic change. While trend results are relatively insensitive to individual outliers, multi-year sequences of extremes can have a significant effect on the test results ifthose sequences occur near the beginning or the end of the period of record used for the test. The sensitivity of trend results to a sequence of extremes depends on the placement of that sequence in the period of record being tested and on the length of the sequence of extremes relative to the length of the record.
Keywords: Dry sequences, Extremes, Outliers, Trends, Wet sequences

SNOTEL - Technology to mitigate natural disaster impacts on a watershed basis - Werner, J.G.; Schaefer, G.L.; Woodward, D. (66th Annual Western Snow Conference, 1998)
SNOTEL (remote data acquisition technology via meteor burst) has been successfully applied mitigating losses from water and climate related natural disasters by the USDA, Natural Resources Conservation Service (NRCS) . Remote SNOTEL sites monitor snow water equivalent of mountain and plains snowpacks, precipitation, air temperature, and soil moisture and temperature. This near real-time information drives predictive analyses (amounts and timing) of seasonal surface water runoff that supplies irrigation and municipalities. Stream flow amounts for fisheries, power generation, river transportation, or flood management are also determined from this data. Recreation and wildlife managers, and building safety engineers rely on this information in making critical design, and management decisions. Decisions are seasonal, event, or emergency based.Non-NRCS resource information is integrated into the analyses for comprehensive understanding of basin, watershed, and effected areas. Results are immediately available by world wide web services, word of mouth in local communities, official reports, news, and by computer access of our data center. Mitigation is achieved: as production is balanced with investments according to the outlooks of the seasonal probability of adequate water supply; advance information about soil moisture shortages or excesses prevent costly mistakes; hourly SNOTEL data monitors critical flood source areas of watersheds during rain or snow, runoff over saturated soils profiles, and extraordinary snowmelt events. Protection of life, property, and sustainable agriculture is the outcome.
Keywords: Forecasting, SNOTEL, Watershed management

Characterization of wind induced show redistribution with GIS derived parameters - Winstral, A.P.; Elder, K.; Davis, R.E. (66th Annual Western Snow Conference, 1998)
In order to develop a physically based model of spatial snow distribution, parameters that characterize the natural controls affecting distribution patterns are necessary. Stratification of the study area, Blackcap Basin, CA, based on timberline indicates that elevation, radiation, and slope exhibit a strong linear relationship to snow depth below timberline, but above timberline the strength of these relationships is greatly attenuated. Based upon field observations of the increased importance of wind redistribution in the exposed alpine region, we apply two terrain parameters which affect wind patterns on the ground to account for this process in our modeling efforts. Surface curvature, a direct output in most Geographic Information System software, and a wind exposure index derived specifically for this study, are tested for their efficacy in explaining the observed alpine snow distribution. The wind exposure index is shown to be abetter predictor of snow accumulation in the alpine region than any of the aforementioned predictor Curvature measured over a large area effectively discriminates convex regions as areas containing anomalously high and low snow depths. An adequate analysis of localized curvature is hindered by both the spatial resolution of the digital elevation model and registration of the data points.
Keywords: GIS, Snow redistribution, Wind direction

1997 Title, Contents, and Minutes (65th Annual Western Snow Conference, 1997)

Overcollection of solid precipitation by a standard precipitation gage, Niwot Ridge, Colorado - Bardsley, Tim; Williams, M.W. (65th Annual Western Snow Conference, 1997)
No Abstract
Keywords: Precipitation gauge, Over-catch, Blowing snow, Niwot Ridge, Solid precipitation

Spatial and temporal variability of Canadian monthly snow depths, 1946-1995 - Brown, R.D.; Braaten, R.O. (65th Annual Western Snow Conference, 1997)
In 1995 the Canadian Atmospheric Environment Service (AES) made a major effort to digitize paper records of daily and weekly snow depth which were not in the Canadian Digital Archive of Climate Data. This resulted in the extension of the snow depth record at many stations back to the late 1940s, and the filling of missing data from a number of stations, particularly in the Arctic. This paper describes the database and the methods used to quality control and reconstruct missing data, and presents an analysis of the spatial and temporal characteristics of the data over the 1946-1995 period. Principal component analysis of monthly snow depths revealed that snow depths varied coherently over relatively large regions of Canada with dominant centres of action located over the West Coast, Prairie, Yukon-Mackenzie, southern Ontario, northern Quebec and Maritime regions. In many cases, nodes of coherent snow depth variations were associated with corresponding nodes of coherent snow cover duration fluctuations, with the two times series exhibiting significant positive correlations. Winter and early spring snow depths were observed to have decreased significantly over much of Canada in the 1946-1995 period, with the greatest decreases occurring in February and March. The snow depth changes were characterized by a rather abrupt transition to lower snow depths in the mid-1970s which coincided with a well-documented shift in atmospheric circulation in the Pacific-North America sector of the Northern Hemisphere.
Keywords: Missing data, Modeling, Principal component analysis

Learning scientific writing through snowpack study - Chisholm, R.M. (65th Annual Western Snow Conference, 1997)
In my course in Technical Writing at Plymouth State College, students learn how to do scientific writing throughsnowpack study. In previous presentations in various publications, I have described the scope and nature of thecourse. This presentation describes how students learn to do scientific writing through both traditional and innovativeactivities. The aims of the course are as follows:Aim I. Learning scientific procedures.Aim 2. Learning and gathering scientific information.Aim 3. Synthesizing, interpreting, and applying scientific information.Aim 4. Creating and participating in a scientific community.Aim 5. Developing the individual scientist.Aim 6. Communicating to the scientific community.These aims are met through a sequence of linked activities, all of which culminate in writing. These activities haveproved effective in helping students learn at every stage from initial field techniques, through learning snow science,to insightful reflection. All activities of the course culminate in a written report. These activities can be adapted for usein other courses on technical and scientific writing as well as in a wide variety of courses on snow science andapplications such as avalanche safety .
Keywords: Avalanche safety, Education, Scientific writing, Snow science, Snowpack, Technical writing

Scale effects in a distributed SWE and snowmelt model for mountain basins - Cline, D.; Elder, K.; Bales, R. (65th Annual Western Snow Conference, 1997)
We present results of an investigation into the effect of increasing spatial and temporal resolutions on modeled distributions of SWE and snowmelt in the Emerald Lake Watershed of the Sierra Nevada of California, U.S.A. We used a coupled remote sensing/distributed energy balance snowmelt model (SNODIS), and used previously validated results from a high spatial (30-m) and temporal (hourly) resolution model run in ELW as a control. We selected spatial resolutions that are commensurate with standard product DEMs or with existing or planned satellite remote sensing data, and temporal resolutions that are factorsof typical operational intervals for meteorological data. We degraded the spatial resolution of the DEM from 30 m to 90, 250, and 500 m prior to computing the distributed micrometeorological data. We degraded the classified remote sensing data to the same spatial resolutions prior to computing the duration of the snow cover. Similarly, we degraded the temporal resolution of the micrometeorological data from 1 hour to 3 and 6 hours prior to computing the distributed energy balance and snowmelt. We compared mean basin SWE, basin snowpack water volume, and the spatial patterns of SWE from each test to our previous, high-resolution results. We found no significant differences between the mean basin-wide SWE computed from the 250-m and 500-m spatial resolutions and that of our high-resolution control, regardless of temporal resolution. At each temporal resolution mean basin SWE was over-estimated at the 90-m resolution by 14-17%. Coarsening of the spatial resolution did result in a loss of explicit information regarding the location of SWE in the basin, as expected. We discuss these results in terms of their implications for applying the SNODIS model to larger regions
Keywords: DEM, Modeling, Satellite, SNODIS

Characteristics of snowmelt from NRCS SNOTEL (SNOwTELemetry) sites - Cooley, K.R.; Palmer, P.L. (65th Annual Western Snow Conference, 1997)
Snowmelt is affected by a number of factors including elevation, slope, aspect, exposure, snowpack depth,surface reflectance and climatic or meteorologic variables such as solar radiation, temperature, wind speed, vaporpressure, and precipitation. Snowmelt models attempt to account for these factors in various degrees from simpleempirical relationships based on air temperature to detailed energy balance procedures. While detailed energybalance models should be superior in estimating snowmelt, there are rarely, if ever, adequate data sets available inpractice to use these methods without making simplifying assumptions. Unfortunately, these simplificationsusually reduce the models' ability to account for the various meteorologic factors that cause snowmelt to occur.Thus the models can produce estimates of snowmelt based on the input data available and the assumptionsrequired, but these estimates may not relate to actual snowmelt in timing or rate. Since actual snowmelt data isvery limited, it is seldom possible to compare model simulated melt rates with actual values. This paper issignificant because it presents an analysis of snowmelt data under a variety of conditions encountered atrepresentative SNOTEL sites selected from nearly 600 locations in the western United States. It thus provides arange of snowmelt information including average and maximum daily melt rates, time of onset and cessation ofmelt, and average day of maximum snowmelt that can be used to compare with snowmelt model simulations andother uses.
Keywords: SNOTEL, Snowmelt rate, Snowmelt timing

Spatially ditrtibuted modeling of snow in the boreal forest: a simple approach - Davis, R.E.; Woodcock, C.; Hardy, J.P.; Nitt, W.; Jordan, R.; McKenzie, J.C. (65th Annual Western Snow Conference, 1997)
Simulations using physics-based, coupled canopy-snow models provided the basis for developing simpleregression models of net energy transfer to snow cover in the boreal forest. The simple models were driven byincoming solar radiation to the top of forest canopies, forest species, tree height and canopy density .Maps of theforest characteristics provided the basis for spatially distributing snow predictions over two test areas in theboreal forest. Over both test areas, variation of incoming solar radiation explained much of the variance in netenergy transfer to snow cover. We found the strongest correlations for the relatively open, discontinuouscanopies of the northern boreal forest.
Keywords: Modeling, Simulation

Estimating spatial distribution of snow water equivalence in a montane watershed - Elder, K.; Rosenthal, W.; Davis, R.E. (65th Annual Western Snow Conference, 1997)
We describe an approach to model distributed snow water equivalence (SWE) that merges field measurements of depth and density with remotely sensed snow-covered area (SCA). In 1993 two teams conducted an intensive snow survey in the 92.8 km2 Blackcap Basin of the Kings River. We measured snow depth at 709 points and density in five snow pits and along five transects using a Federal Sampler. Sample locations were chosen to be representative of the range of elevations, slopes and aspects of the basin. Regression tree models showed that net radiation, elevation, and slope angle account for 60- 70% of the variance in the depth measurements. Density was distributed over the basin on a 30 m grid with a multiple linear regression model that explained 70% of the observed variance as a function of the same three variables. The gridded depth estimates combined with modeled density produced spatially distributed estimates of SWE. An unsupervised spectral unmixing algorithm estimated snow cover fractions from Landsat-5 Thematic Mapper data acquired at the time of the snow survey. This method provides a snow cover fraction estimate for every pixel. We used this subpixel map as our best estimate for SCA and combining it with the SWE map allowed us to compute SWE volume. We compared the estimated volume using the subpixel SCA map with several SCA maps produced with simulations of binary SCA mapping techniques. Thresholds of 40%, 50% and 60% fractional cover were used to map binary cases of full snow cover or no snow cover. The difference in basin SWE volume was up to 13% depending on the threshold used to classify snow-covered versus snow-free areas. The percent differences in volumes roughly couesponded to the percent differences in SCA between the methods.
Keywords: Kings River, LandSat, Modeling

Stepwise multiple regression snow models: GIS applications in the Marmot Creek basin, (Kananaskis Country, Alberta) Canada and the National Park Berchtesgaden, (Bayern) Germany - Forsythe, K.K. (65th Annual Western Snow Conference, 1997)
Geographic Information Systems (GIS) and satellite remote sensing are now used extensively in analyses of natural environments. This research examined the usefulness of a GIS and remote sensing based approach for integrating many different and widely varying data sources. The multisource data sets were used in stepwise, multiple linear regression models that analyzed the variation in snow dept and snow-water equivalent (SWE) depth.Models were developed in the Marmot Creek Basin using landsat Thematic Mapper (TM) satellite data, Digital Elevation Model (DEM) data and various mapped data layers in combination with historical snow depth and SWE measurements. The best model for snow depth produced a coefficient of determination or adjusted R2 of 0.6370. The independent variables of elevation, incidence, tree height and principal component four of the TM data could explain approximately 64% of the variation in snow depth. The best model for SWE depth had an adjusted R2 of 0.5814. The independent variables that explained the variation in SWE depth were elevation, incidence, and TM band seven. The National Park Berchtesgaden models build upon the approach used in the Marmot Creek Basin. landsat TM data and a DEM provided the basis for the regression independent variables. Additional analyses of these data were performed within the GIS to calculate variables such as across and down slope curvature and a Normalized Difference Vegetation Index (NDVI). The best model for snow depth produced an adjusted R2 of 0.801 while the SWE result was 0.843. The variables providing the explanation in snow depth variation were elevation and NDVI. SWE depth variation was explained by elevation, across slope curvature, TM band seven and principal component four of the TM data.
Keywords: GIS, Landsat, Modeling, Principal component analysis, Thematic Mapper

'Hydro-fuels-', Maintenance-, and Pricing Risk Management -Changing Times in Snow Zone Water Management - Gary J Freeman (65th Annual Western Snow Conference, 1997)
In August 1996, the California Legislature passed legislation (AB 1890) that established new policies and restructured California's electric Industry. The Bill established an Independent System Operator (ISO), a Power Exchange (PX), a rate-reduction financing program, a public benefits program, and called for increased system reliability. With the deregulation of California's electric utility industry taking place, the water management team at Pacific Gas and Electric Company (PG&E), an investor owned utility, is facing a new challenge. Future pricing uncertainty will likely become as important to snow zone reservoir management as seasonal remaining weather uncertainty has traditionally been for forecasting snowmelt runoff and maximizing hydro generation in the past. While PG&E has been utilizing probabilistic extended streamflow predictions for some time in making hydroelectric scheduling decisions, it has only recently begun to look at how weather uncertainty will be handled by energy traders that are selling electricity into the California Power Exchange and eventually into a futures market. Electricity futures market pricing (one to three months ahead) is beginning to have a significant effect on how much risk an operator may be willing to take with regard to storing water in anticipation of a better price at some future date. In a sense, water is perishable with regard to use for hydro generation. If stored, there is risk that the weather could turn wet and that water may be spilled past fully loaded powerhouses
Keywords: Pacific Gas & Electric, AB 1890, ISO, Deregulation

Impact of climate warming to the droughts of Canadian Prairies - Gan, T.Y.; Singh, P.R.; Seneka, M. (65th Annual Western Snow Conference, 1997)
Results from applying Kendall's test to 37 stations of temperature and precipitation data, 50 stations of natural streamflow data and 13 stations of evapotranspiration data show that the Prairies have become warmer and somewhat drier in the last four to five decades. The earlier onset of spring snowmelt runoff detected by Bum (1994) further supports this finding. Results on Kendall's test on precipitation, natural streamflowand areal ET indicate that the Prairie may have become drier but the trends detected are less extensive when compared to wanning trends. The correlation-distances reveal that temperature data are generally more correlated to each other than precipitation data. The bivariate precipitation versus maximum temperature test failed to detect any link between precipitation and temperature and Kendall's test on the drought duration, severity and magnitude prepared by Bauer and Welsh (1988) for two sites in Saskatchewan also shows no significant trend in the Prairie drought.
Keywords: Climate change, Drought, Kendall's test

A detector for determining snow water content based on attenuation of cosmic radiation - Gehrke, F. (65th Annual Western Snow Conference, 1997)
Water content of the snow pack is measured at approximately 100 sites within the State of California by snow sensors. The sensors detect the water content as a weight exerted on either stainless steel or rubber bladders filled with fluid. The tanks are connected to either a stilling well with a shaft encoder or a pressure transducer. The resulting signal is proportional to the weight of the water in the snow. These sensors suffer from a variety of problems. They require a large footprint, at least 7.5 square meters to avoid edge effects, with consequent environmental disruption. The tanks and associated plumbing are prone to puncture from both human and animal disturbance. Transport of the bladders poses significant t difficulties in wilderness areas where mechanical transport is prohibited. Loss of the sensors for an entire season is not uncommon due to water intrusion into the transducer or leaks in the tanks. Adding insult to injury, the sensors do not accurately measure the water content under certain conditions. Extensive ice layers in the snow can support part of the pack's weight so that the registered water content is less than actual. Later, after these layers lose some of their structure, or additional snow accumulates to collapse the bridging structure, the sensor readings will reflect actual snow water content.This paper will describe the development of a detector which measures cosmic radiation and determines the snow water equivalent based on the attenuation of the radiation. The detector has had two seasons of field verification tests at the Central Sierra Snow Laboratory with very promising results.
Keywords: Pressure transducer, Radiation attenuation, Snow pillow

Field measurements of snowdrift development rate - Haehnel, R.B.; Lever, J.H.; Tabler, R.D. (65th Annual Western Snow Conference, 1997)
For successful snow drift modeling, similitude of drift geometry and development rate must be preserved betweenmodel and prototype. Earlier work revealed that field data documenting drift development are scarce, yet such dataare necessary to validate proposed modeling methods. This requires measurement of the evolving drift topographyand concurrent measurement of the incident mass transport and flow field throughout the drifting event. The authorsestablished a field program to measure drift development on a two-dimensional solid fence during the winters of1996 and 1997 at two field sites located in Wyoming. The developing drift topography was measured usinggraduated snow stakes placed around the objects. The incident mass transport was measured using a Wyoming snowfence as a snow trap. The incident flow field was also documented. Here we compare prototype drift geometries and development rates with corresponding preliminary model data obtained in a snow drifting wind tunnel. The field data revealed some inaccuracies in the model drift geometry anddevelopment rate which might result from distortion in snow transport concentration and particle trajectory lengths. Further work is required to minimize the effects of model distortions. The field data obtained in this work will serve as benchmark data for evaluating modeling methodologies.
Keywords: Drift topography, Modeling, Similitude, Snow drifting, Snow management

Comparison of average annual precipitation distributed by different GIS models for the Bitterroot Watershed, Montana - Hammer, R.G.; Farnes, P.E.; McLeod, R.A. (65th Annual Western Snow Conference, 1997)
No abstract
Keywords: GIS, PRISM model

Snow ablation modeling in conifer and deciduous stands of the boreal forest - Hardy, J.P.; Davis, R.E.; Jordan, R.; Ni, W.; Woodcock, C. (65th Annual Western Snow Conference, 1997)
Both coniferous and deciduous forests alter the energy exchange and the accumulation and ablation of snow on the ground. Snow ablation modeling at the stand scale presents challenges to account for the variability in snow cover and the large variations of solar and thermal radiation incident to the forest floor. Previous work by the authors coupled a one-dimensional snow process model (SNTHERM), modified for forested conditions, with a model of radiation interactions with forest canopies to successfully predict snow ablation in a mature jack pine stand. Now, we use the same approach and model snow ablation in black spruce and aspen stands and verify the modeling effort by comparison with field data. A new routine is added to SNTHERM to account for forest litter on the snow surface, thereby affecting the albedo. We conducted field work during March 1996 in central Saskatchewan. We measured snow pack physical properties, meteorological parameters within the forest canopy, and incoming solar and thermal irradiance beneath the forest canopy. At peak accumulation snow depths in black spruce tree wells were approximately 65% of that measured in forest gaps. Snow in the aspen stand ablated 26 days before snow in the black spruce stand and both results compare favorably with available measured data.
Keywords: Ablation, Aspen, Black spruce, Jack pine, Modeling

Atlantic ocean atmosphere interactions and snowfall in southern New England - Hartley, S. (65th Annual Western Snow Conference, 1997)
This paper examines in further detail a previously identified inverse association between seasonal snowfall totals in southern New England and sea surface temperature anomalies (SSTAs) in the adjacent Atlantic Ocean. Variations of western Atlantic SSTAs and of the rnid-tropospheric circulation over North America and the adjacentAtlantic Ocean during the cold-season months ofOctober-March are each examined by principal component analysis.Canonical correlation analysis identifies the dominant modes ofjoint variability (contemporaneous and lagged) between Atlantic SST As and the atmospheric circulation. Comparisons are made between HIGH-SNOW and LOW-SNOW winters. Results suggest that the rnid-tropospheric circulation of December has a disproportionate influence on seasonal snowfall. Persistence of Atlantic SST As established partly through atmosphere-ocean coupling in the late fall/early winter is proposed as a possible linkage. The extent to which the SST As then influence precipitation form is still currently under investigation, but there are indications that SST As might influence the Atlantic Coast storm track, as well as air temperatures in southern and coastal New England.
Keywords: Atlantic Ocean, Ocean circulation, Ocean temperature, Seasonal snowfall

Acumulation of intercepted snow in the boreal forest: Measurements and modelling - Hedstrom, N.R.; Pomeroy, J.W. (65th Annual Western Snow Conference, 1997)
A new snowfall interception model is introduced. The model incorporates physically-based processes to scale from the branch to canopy. Previous models of snow interception have neglected the persistence of intercepted snow load and the effects of temperature on maximum intercepted load and hence have only been applicable to climates where snow is regularly and quickly lost from the canopy. To investigate snow interception at the forest stand scale, measurements of above and subcanopy snowfall, accumulation of snow on the ground and the load of snow intercepted by a suspended, full-size conifer were collected from boreal forest spruce and pine stands. These data show that interception increases with increasing snowfall, to a point when the intercepted load overcomes the strength of branches to support it. Hence, the interception efficiency decreases with snow load and amount of fresh snowfall. Leaf area index, tree species and initial snow load determine the maximum canopy snow storage. The maximum storage, canopy coverage and snowfall are used to calculate snow interception for a canopy, presuming exponential decay in incremental interception as the amount of snowfall increases. The sensitivity of the model to temperature, wind speed and other factors is examined. This method can be used to calculate snow interception over an entire winter period using relatively standard meteorological and forest inventory variables.
Keywords: Interception, Modeling

The effects of light intensity and blu, green and red wavelengths on mating strategies in the snow alga, Chloromonas sp -d, from the Tughill Plateau, New York State - Hoham, R.D.; Kang, J.Y.; Hasselwander, A.J.; Behrstock, A.F.; Blackburn, I.R.; Johnson, R.C.; Shlag, E.M. (65th Annual Western Snow Conference, 1997)
In this study, four strains of the snow alga, Chloromonas sp.-D, were isolated from the Tughill Plateau, Whetstone Gulf State Park, NY, to study mating strategies under different light conditions. Experiments were conducted in white acrylic test tube holders that were placed in growth chambers with controlled light, temperature and photoperiod. Two light sources were used, Wide-Spectrum (WS) and CooI-White (CW), and the effects of blue, green and red light were tested by covering the holders with corresponding cellophanes. Cells were fixed with OsO4 and observed and tabulated using Zeiss phase-contrast microscopes. Using similar light intensities, blue light regimes produced more matings than green light regimes in four of four trials (two were significantly different, P<0.05), and blue light regimes produced more matings than red light regimes in seven of eight trials (three were significantly different, P<0.05). There were no trends in mating when green and red light regimes were compared in three trials. A photon light intensity of 200 I'mol m-2 S-I produced the most mating under both WS and CW regimes, but more mating occurred under CW in all intensities tested. When red light regimes of higher photon intensity (180 I'mol m-2 S-I) were compared to those of blue light regimes of lower intensity (60 I'mol m.2 S-I), more mating occurred under red light in four of four trials, but none were significantly different. Mating pairs of three types were observed: oblong-oblong (o-o), oblong-sphere (o-s) and sphere-sphere (s-s). Cell packs that produced mating types and o-o mating pairs diminished with time. However, o-s and s-s mating pairs and quadriflagellate zygotes produced from the mating pairs increased with time.
Keywords: Chloromonas, Light intensity, Light wavelength, Mating

The impact of glacier recession upon the discharge of the Bow River above Banff, Alberta, 1951-1993 - Hopkinson, C.; Young, G. (65th Annual Western Snow Conference, 1997)
Three methods were used to determine the net volumetric loss (wastage) of glacier cover within the Bow Valleyabove Banff, Alberta between 1951 and 1993 (see Hopkinson, 1997). It was estimated that between 1100 and 1650 m3 x 10 to the 6th of ice volume was lost during this time period. The median value of 1375 m3 x 10 to the 6th was converted to a water equivalence value of approximately 1170 m3 x to the 6th by assuming a glacier ice (including firn and voids)/water ratio of approximately 85%.The bulk glacier wastage estimate was divided into proportions using the Peyto Glacier mass balance record. Unfortunately, the record began in 1966 and a back-cast to 1952 was necessary. Banff maximum summer temperature and Lake Louise snow course data were used as surrogates for summer and winter glacier mass balance, respectively. Seasonal wastage contributions to river flow were estimated for 1967 to 1974 using modelled values of glacial melt (ice and firn only) generated for Peyto Creek by Young ( 1982).An estimate of the temporal variation of glacier recession inputs to the Bow River hydrograph at Banff was facilitated by comparing known basin yields with the modelled wastage values. For 1952 to 1993, the average annual wastage/basin yield ratio is found to be around 2.3%. For the extremely low flow year of 1970 this ratio increases to 12.5%. The proportion of flow derived from glacier recession in August of this year is estimated to be around 53%. It is thought that the mass balance back-cast may slightly under-estimate wastage values in the early part of the time series, therefore, leading to an over-estimation later on.
Keywords: Glacier melt, Glaciers, Mass balance, Wastage

The net volumetric loss of glacier cover within the Bow Valley above Banff, 1951-1993 - Hopkinson, C. (65th Annual Western Snow Conference, 1997)
Three methods have been used to explore the volumetric change of glaciers in the Bow Basin above Banff forthe years 1951 to 1993. Using aerial photography, the extent of glacier covers for the two years were mapped at a scale of 1 :50,000. The first volumetric calculation of glacier loss was based on inventory criteria (Stanley, 1970); the second a hypsographic curve method based on Young's investigations in Mistaya Basin (1991) and the third; stereo air photogrammetry and DEM comparisons using the computer software package Surfer. These methods were applied to the highly glacierized Hector Lake catchment within the Bow Valley and then extrapolated up to the whole basin above Banff. Reasonable agreement was achieved between the methods and the magnitude of net glacier loss from 1951 to 1993 is estimated to be 1100 to 1650 m³ x 10^6. The true value for volumetric change is considered to be towards the upper end of the range given, due to the likelihood for systematic underestimation during the extrapolation up to the basin above Banff.
Keywords: Bow Valley, DEM, Glacier recession, Surfer, Volume change

Snowpack chemistry as an indicator of pollutant emission levels from motorized winter vehicles in Yellowstong National Park - Ingersoll, G.; Turk, J.; McClure, C.; Lawlor, S.; Clow, D.W.; Mast, A. (65th Annual Western Snow Conference, 1997)
Wintertime visitors to Yellowstone National Park, Wyoming, consider scenery, wildlife, and clean air as three important qualities of their experience in the Park. Because the majority of winter visitors tour Yellowstone by motorized winter vehicles, and winter visitation has increased nearly tenfold since 1968, the effects of vehicle use are a growing concern for resource managers. The extent of effects on air quality and ecosystem health from increasing vehicular emissions throughout the Park is not fully understood. Snowpack chemistry provides a composite record of atmospheric deposition of airborne pollutants throughout winter. Pollutant levels from vehicular emissions inside the Park were characterized by snowmelt-chemical data from three sites at a variety of high- and low-traffic locations. At each site snow samples representing most of the annual snowpack were collected at an off-road site 20 m to 100 m from motorized-traffic routes, and at a site directly in snow-packed roadways used by over-snow vehicles. Snowmelt chemistries were compared between these three pairs of samples collected in-road and off-road to determine whether concentrations decreased with distance from the source. Concentrations of ammonium, nitrate, and sulfate in snowmelt positively correlated with vehicle usage. Ammonium and sulfate levels were consistently higher for the in-road snow compared to off-road snow for each pair of sites, but nitrate concentrations did not decrease within a distance of 100 m from the emission source. This method demonstrates that snowpack chemistry can be used as a quantifiable indicator of airborne pollutants from vehicular traffic. A correlation was shown between pollutant levels and vehicle traffic. Additional results indicate the nitrate ion may be used to distinguish between local and regional emissions sources.
Keywords: Nitrates, Oversnow vehicles, Pollutants, Snowmobiles

Coal Lake outlet freeze-up, containment of winter inflows and estimates of telated outburst flood on Wolf Creek, Yukon Territory - Jasek, M.; Ford, G. (65th Annual Western Snow Conference, 1997)
Spring snowmelt is generally the dominant annual peak flow generating mechanism in subarctic regions, thoughsmaller basins may occasionally experience peak flow events due to summer rain storms. An unusual lake outburstflood event was observed at Wolf Creek, a small tributary of the Yukon River. The event was focused at the outletof Coal Lake the only major storage element in the basin.During the unusually cold January of 1996 ice growth at the outlet of Coal Lake created an ice dam which progressively grew through aufies formation as the lake levels increased. The ice dam failed in late April approximately 9 days after the onset of mean daily positive temperatures sending a significant flood wave downstream. This event was in excess of 1996 freshet flows which occurred more than one month later.There are three hydrometric stations on Wolf Creek however these were not activated until the recession of the outburst event. A water balance was carried out to reconstruct this flood event using observed lake levels for the containment period, the recorded recession limbs of hydrographs at the Coal Lake hydrometric station and a downstream hydrometric station, winter recession flows at an upstream hydrometric station and personal observation.The analyses indicated that the outburst event was greater in magnitude than the subsequent freshet event. In addition to facilitating the reconstruction of the annual hydrograph, the analyses provides valuable information on a little known strearnflow generation mechanism in small subarctic basins with lake storage.
Keywords: Coal Lake, Spring freshet, Wolf Lake, Yukon River

River basin variations in Sierra Nevada snowpack accumulation trends - Johnson, T.; Dozier, J.; Michaelsen, J.; Fohl, P. (65th Annual Western Snow Conference, 1997)
Mountainous areas, particularly in the western United States, provide a large fraction of the fresh water supply. This reserve, which supplies most of California's growing water needs, is vulnerable to changes in climate. Regional precipitation patterns, especially snow, which is a sensitive indicator of change, are predicted to vary according to future climate models. This study uses a statistical model which links snow water equivalent (SWE) measurements over a 6O-year time series to analyze the snow accumulation trends in the Sierra Nevada.We utilized snow course measurements with data difficulties including inconsistent monthly sampling, added and removed stations and possibly a few moved or otherwise altered snow courses. To determine the effects of a monthly and irregular sampling schedule we analyzed daily snow sensor data spanning 25 years. Furthermore, we employed a statistical test to check for possibly discontinuous snow course stations.We found that the overall maximum amount of seasonal SWE is not changing. However, below 2700 meters, snowmelt timing has recently been occurring earlier, whereas elevations above 2900 meters are melting later. The eastern draining river basins consist of steeper, drier slopes that have mostly increasing SWE trends. The Owens River basin, in the southeastern tip of the range, has gained the most SWE while the neighboring, westside Kern has received less snow.
Keywords: Climate change, Precipitation patterns, Statistical model

Snowpack characteristics of an alpine site in the Sierra Nevada - Kattelmann, R.C. (65th Annual Western Snow Conference, 1997)
A snow research site has been operated on Mammoth Mountain in the eastern Sierra Nevada of California since 1978. Records from this timberline study plot illustrate some of the characteristics of snowpack development and ablation in the high Sierra Nevada. In most years, a snowpack of at least 50 cm depth has been in place by the first of December. Mid-winter storms have deposited a few centimeters to a few meters of snowfall. Wind redistributes snow around the site and is a critical influence throughout the accumulation season. Snow depth usually reaches a maximum sometime in April. Over the period of record, peak depths have ranged from 2 to 8 m with water equivalence of 0.7 to 2.5 m Sustained spring snowrnelt usually begins in late April or early May after storms have become infrequent. Daily melt amounts in May tend to average about 20 mm per day Snow cover usually disappears during June but has persisted until August.
Keywords: Mammoth Mountain, Redistribution, Snowmelt

Very warm storms and Sierra Nevada snowpacks - Kattelmann, R.C. (65th Annual Western Snow Conference, 1997)

Application of SLURP hydrological model to a sub-arctic basin - Li, B.; Kite, G.; Haberlandt, U. (65th Annual Western Snow Conference, 1997)
The SLURP model developed at NHRI, is a distributed conceptual model which simulates the behaviour of a watershed by carrying out vertical water balances for each element of a matrix of land covers and subareas of a watershed and then routing the resulting runoff between subareas. The model is able to simulate snowpack accumulation and depletion, groundwater response of watersheds, and rainfall and snowmelt generated streamflow. This study describes an approach of applying the SLURP hydrological model to a mountainous sub-arctic streamflow of Wolf Creek Basin. In this sub-arctic region, annual peak flow is generally dominated by snowmelt. As a research basin, the Wolf Creek basin has been equipped with instruments to measure the snow depth and density. A procedure to convert snow data time series into winter precipitation required by SLURP is developed. The generated winter precipitation data, together with other related climate data from three meteorological stations within the basin were used for both model calibration and model verification. Two years of streamflow data were tested with good results obtained for the calibration period 1994-1995 and somewhat lesser for the verification period 1995-1996.
Keywords: Grid model, Model application, Snow accummulation, Snow depletion

Spatially distributed snowmelt inputs to a semi-arid mountain watershed - Luce, C. H.; Tarboton, D.G.; Cooley, K.R. (65th Annual Western Snow Conference, 1997)
Spatial variability in snow accumulation and melt due to topographic effects on solar radiation, drifting, air temperature, and precipitation is important in detennining the timing of snowmelt releases. Precipitation and temperature effects related to topography tend to affect snowpack variability at large scales and are generally included in models of hydrology in mountainous terrain. The effects of spatial variability in drifting and solar input are generally only included in distributed models at small scales. Previous research has demonstrated that snowpack patterns are not well reproduced when topography and drifting are ignored. These observations imply that larger scale representations that ignore drifting could be greatly in error. Detailed measurements of the spatial distribution of snow water equivalence within a small, intensively studied, 26-ha watershed were used to validate a spatially distributed snowmelt model. This model was then compared to basin-averaged snowmelt rates for a fully distributed model, a single point representation of the basin, a two point representation that captures some of the variability in drifting and aspect, and a model with distributed terrain and uniform drift. The model comparisons demonstrate that the lumped, single point representation and distributed terrain with uniform drift both yielded very poor simulations of the basin-averaged surface water input rate. The two-point representation was an improvement but the late season melt required for the observed streamflow was still not simulated because the deepest drifts were not represented. These results imply that representing the effects of subgrid variability of snow drifting is equally or more important than representing subgrid variability in solar radiation.
Keywords: Modeling, Reynolds Creek, Sheep Creek

Historic role of fire in determining annual water yield from Tenderfoot Creek Experimental Forest, Montana, USA - McCaughey, W.W.; Farnes, P.E.; Hansen, K.J. (65th Annual Western Snow Conference, 1997)
Water production from mountain watersheds depends on total precipitation input, the type and distribution of precipitation, the amount intercepted in tree canopies, and losses to evaporation, transpiration and groundwater. A systematic process was developed to estimate historic average annual runoff based on fire patterns, habitat cover types and precipitation patterns on the Tenderfoot Creek Experimental Forest. A fire history study in the Little Belt Mountains of central Montana indicates much of the experimental forest watershed burned in the 1700's and 1800's. Fire scars and existing timber stands on the 3,709 ha experimental forest show that two fires occurred in the 1700'sand six in the 1800'5 covering more than 1,660 ha (45 percent) and 2,415 ha (65 percent), respectively. One small 32 ha stand on the experimental forest has not burned since 1580. The last major fire (206 ha) occurred in 1902 and three other small fires (covering only 19 ha) have been observed since the implementation of active fire suppression in the early 1900's. There has been no logging on this 3,709 ha forest of which 9 percent of the total area is composed of non-timbered meadows or rock outcrops. Annual water yield was estimated for Tenderfoot Creek Experimental Forest for the past 400+ years utilizing fire history, habitat cover types, current average annual precipitation and water yield/precipitation/cover type relationships. The maximum average annual runoff was estimated at 12,480 cubic decameters (dams3) in the late 1500's based on 30 years ofaverage annual precipitation (1961-1991) .The 1581 to 1997 average water yield was estimated to be 11,680 dams3. The maximum water yield estimated for Tenderfoot Creek Experimental Forest, if all timber were removed, would be around 13,240 dams3. The minimum runoff if the entire forest was composed of mature lodgepole pine would be 11,230 dams3. The present yield of 11,360 dams3 is near the lowest yield of 11,250 dams3 estimated for 1873 and near the minimum possible for this experimental forest. During a wet year with all of the timber removed, runoff could be as high as 21,190, or in a ary year with most of the watershed covered with a mature forest as low as 5,620 dams3. On TCEF, fire suppression and succession appear to be creating conditions for a major fire event unless portions of the forest are removed by management actions that mimic historic vegetation patterns.
Keywords: Fire history, Water yield

An operational distributed snow dynamics model fot the Sava River, Bosnia - Melloh, R.; Daly, S.; Davis, R.E.; Jordan, R.; Koenig, G. (65th Annual Western Snow Conference, 1997)
A method of estimating and forecasting snow pack dynamics for a large remote basin in Bosnia was developed and consists of a highly automated, spatially distributed model for operational simulation and forecasting of snow pack depth, snow water equivalent, soil freeze-thaw state, and flux of snow melt and rain infiltration to the base of the pack. The model, applied to hydrologic forecasts in Bosnia during the winter of 1996-1997, has potential use in domestic flood and water supply forecasting. SNTHERM, a complex one-dimensional energy balance model that takes into account most physical processes within the snow cover, was used for snow pack computations. The model was distributed across the landscape by 1-km pixels, using a categorical classification of the basin into 216 slope, aspect and meteorology types. The model system was highly automated. Runoff ratios (runoff/rainfall) forthe winter of 1996-1997 compared well to long term average runoff coefficients, indicating precipitation data used to drive the model were reasonable. Supporting research issues are discussed.
Keywords: Infiltration, Model, Snowmelt, SNTHERM, Water supply forecasting

Spatially distributed snowmelt rates in a boreal forest basin - Metcalf, R.A.; Buttle, J.M. (65th Annual Western Snow Conference, 1997)
Spatial variation in snowmelt rates in the boreal forest can be explained by differences in canopy density. Canopy density, represented as gap fractions (GF), controls both the anlount of shortwave radiation reaching the snov.pack surface and wind speed over the snow surface, which in turn regulates sensible and latent heat fluxes These reductions outweigh any increased contributions from longwave radiation as a result of increased biomass. Differences in the total energy available for melt do not translate to equally proportional changes in melt rates under different canopy densities. As available energy increases, the melt rate increases with decreasing canopy density and the form of therelationship can vary depending on climatic conditions. A good relationship between ground-based GF measurements and a canopy closure index derived from Landsat TM, provides the spatial fabric for the physically-based distribution of snowmelt rates that shows comparable patterns of snow ablation during years of very different climatological conditions. This physically-meaningful method of determining the spatial variability of meltwater delivery to the soil interface provides a better understanding of the heterogeneous active layer development and runoff processes in the boreal forest.
Keywords: Boreal Forest, Clearings, Gap functions, Snowmelt

Snow accumulation under farious forest stand densities at Tenderfoot Creek Experimental Forest, Montana, USA - Moore, C.A.; McCaughey, W.W. (65th Annual Western Snow Conference, 1997)
Snow accumulation in forested watersheds is controlled by climate, elevation, topographic factors and vegetation structure. Conifers affect snow accumulation principally by intercepting snow with the canopy which may later be sublimated. Various tree, stand, species and canopy densities of a subalpine fir habitat (ALBANASC) in central Montana were studied to determine if there was a response of snow accumulation to vegetation. Tree canopy cover, basal area, age since stand initiation, and species composition were measured at several sites with minimal topographic differences. Peak snow water equivalent was measured at 270 sample points within 8 stands divided between 3 study areas and at three corresponding open meadows. The study took place during the winter of 1995-1996 on the Tenderfoot Creek Experimental Forest in the Little Belt Mountains near Great Falls, Montana. It is administered by the USDA Rocky Mountain Research Station.Variation in peak accumulation (SWE) on the forest floor was impacted the greatest by the percent of canopy cover measured by the 30deg view angle of a photocanopyometer. Half of the variation in snow accumulation can be attributed to variation in canopy cover. A 6.4 percent decrease in peak snow water equivalent was observed per 10 percent increase in canopy density. Snow samples under subalpine fir and Engelmann spruce canopies showed a closer correlation between canopy and peak snow water equivalent than did lodgepole pine canopies. Basal area was found to be a poor predictor of snow accumulation.
Keywords: Basal Area, Engelmann spruce, Interception, lodgepole pine, subalpine fir

An investigation of the thermal properties of traditional snow shelters - Mueller, D. (65th Annual Western Snow Conference, 1997)
Traditional snow shelters have been constructed and used byindigenous groups for centuries. Modern sciencehas done little to quantify and compare the thermal properties of these structures. In February 1995, three snow shelters (an igloo, snow cave and quinzee) were built near the Montmorency Forest Research Station in the Laurentides, Quebec. Eight copper-constantan thermocouples were placed at intervals throughout the wall, outside and inside each snow shelter (on the floor, in the cold air trap and near the roof). During the night, temperatures were recorded using a Campbell Scientific 21X datalogger in the occupied structure. Thermal conductivities of the snow walls were calculated for each shelter. The wall of the igloo had the lowest thermal conductivity (k = 0.27 W/m/K), followed by the snow cave wall (k = 0.36 W/m/K. The quinzee wall had the highest thermal conductivity (k = 0.56 W/m/K. The results indicate that the igloo wall was the best insulator out of the three snow shelter types.
Keywords: Igloo, Quinzee, Snow cave, Snow shelters, Thermal conductivity

Local advection of sensible heat during snowmelt - Neumann, N.; Marsh, P. (65th Annual Western Snow Conference, 1997)
Heterogeneous land surface characteristics during the spring melt of an Arctic snowpack produce a horizontal transfer of energy at a small scale, a process termed local advection. Techniques were developed and applied to determine the importance of this local scale advection to both the magnitude of snowmelt and the average flux from a composite snow and snow-free surface. A tile-model approach was evaluated in estimating the spatial sensible heat flux over a patchy snow cover by comparison to eddy correlation measurements. These results suggest that a simple tile model is sufficient in determining the sensible heat flux over a heterogeneous surface, agreeing with other studies. An advection efficiency term, calculated from both field data and published model results (Liston, 1995), was used to determine the effect of advection on local snowmelt patterns. These calculations resulted in different patterns of influence, probably due to differences between the ideal modelled and natural surface conditions.
Keywords: Arctic, Model, Patchy snow

Development of the prairie blowing snow model for application in climatological and hydrological models - Pomeroy, J.W.; Li, L. (65th Annual Western Snow Conference, 1997)
The Prairie Blowing Snow Model (PBSM) is a single colwnn, physically-based, mass and energy balance that calculates blowing snow transport and sublimation rates. New features of the model include a correction for snowfall undermeasurement, mid-winter snowmelt, snow density estimates and estimation of the effect of exposed vegetation on aerodynamic roughness height during blowing snow. Importantly, the model now includes algorithms to estimate the threshold wind speed for snow transport and to estimate the probability of blowing snow occurrence. The probability of blowing snow occurrence is used to scale the blowing snow fluxes horizontally so that estimates from a 1 x 1 km surface area control volume may be extrapolated to larger scales, varying fetches and vegetation types. As a demonstration, the model is operated using standard meteorological data from meteorological stations in the Canadian Prairies and compared to snow accumulation measurements at these stations. The model is also used to estimate snow accumulation for comparison to extensive field snow surveys from the Bad Lake experimental basin in west-central Saskatchewan. It is shown that the new version of PBSM can provide estimates of snow accumulation, melt, transport and sublimation from hourly to seasonal time periods for varying land surfaces.
Keywords: Model, PBSM, Roughness, Snow transport, Sublimation

The interactive multisensor snow and ice mapping system - Ramsay, B.H. (65th Annual Western Snow Conference, 1997)
The Interactive Multisensor Snow and Ice Mapping System (IMS) was developed to give snow and ice analysts the tools, on one platform, to visually inspect imagery and mapped data from various sensor sources to determine the presence of snow and ice and to depict snow and ice covered areas on a map on a daily basis, in one hour or less. Snowand ice analysts in the National Environmental Satellite, Data, and Information Service have been creating weekly maps showing the extent of snow cover for the Northern Hemisphere since 1966 using visible imagery from polar-orbiting and geostationary satellites and surface observations as data sources. The current process is mostly manual and time consuming, taking up to 10 hours to produce a map during the snow season. Where cloud cover precludes an unobstructed view of an area during the entire week, the analysis from the previous week is carried forward. Each week the analyst draws a new map by hand, then digitizes the extent of snow and ice cover using an 89x89 line grid overlaid on a stereographic map of the Northern Hemisphere. The hand drawn map is photocopied and distributed and the digitized map is saved to a file for use in National Weather Service numerical models and for archival storage. IMS was designed and built to replace and improve this process by producing a more accurate, timely product.
Keywords: IMS, Mapping, Satellite, Snow surface

An experiment in use of seasonal long-range weather forecasts for water supply forecases in northern California - Roos, M.; Ross, C. (65th Annual Western Snow Conference, 1997)
From 1978 through 1992 Scripps Institution of Oceanography made quarterly long-range weather forecasts of precipitation in the Sierra Nevada. The 15 year experiment showed some skill in the winter and spring season. In the 1980s an attempt was made to apply the skills that existed to an early season December 1 forecast of water year runoff on selected rivers. The methodology of adjusting the conventional runoff forecast and the conventional expected range of runoff (which are based on climatology for future weather) for the demonstrated weather forecasting skill will be described in the paper. Some test results are shown. Unfortunately, the weather forecasting skills declined during the period of hydrological testing to below the threshold of usefulness and the forecasting experiment was put aside for a later time. But we believe there is merit to documenting the methodology and results of this experiment for other professionals.
Keywords: Long range, Streamflow forecasts, Weather forecasts

Determination of snow covered area using RADARSAT imagery on two small test sites in southern Ontario - Seglenieks, F.; Soulis, E.D.; Kouwen, N. (65th Annual Western Snow Conference, 1997)
This study was perfomed in order to determine if the areal extent of a wet discontinuous snowcover could beeffectively mapped using a RADARSAT image. The sites chosen for the experiment were two agricultural areaslocated in soudiern Ontario. On March 27, 1997 oblique arial photography was acquired and used to create aground reference map for two sites, showing the location of bare ground and snowcovered ground in selectedfields. On March 26, 1997 a RADARSAT C-HH SAR image was acquired, which was classified into bare groundand snowcovered ground and then compared to the ground reference map. The classification accuracies were62.3% and 67.3% for the sites, however the percent snowcovered area was calculated to be within 5% of theground reference map estimate after accounting for the melt that occurred in the day between the acquisition of thetwo images.
Keywords: Agricultural areas, Arial photography, RADARSAT images, Snow cover

Effects of climate change on water resources and runoff in an alpine basin - Seidel, K.; Ehrler, C.; Martinec, J. (65th Annual Western Snow Conference, 1997)
The combined influence of increased temperatures and changed precipitation on the seasonal snow cover and runoff is evaluated for the upper Rhine basin at Felsberg (3250 km2, 560-3614 m a.s.l.). The runoff regime reflects the snow accumulation in the winter half year and snow-melt in the summer half year. The method of predicting future runoff regimes is based on high resolution periodical snow cover mapping by satellites in order to evaluate the climate-effected snow cover and runoff by the SRM-ETH model. Conditions of the present climate are represented by a nonnalised year. Snow conditions and yearly hydrographs are evaluated for the years 2030 and 2100 according to the given climate scenarios for this region. Quantitative results indicate the decrease of the snow accumulation on 1 April as well as the seasonal redistribution and changes of runoff.
Keywords: Model, Precipitation change, Runoff regime, Satellite, Seasonal snowcover, SRM-ETH, Temperature change

Measurement of differences in snow accumulation, melt, and micrometeorology between clearcut and mature forest stands - Storck, P.; Kern, T.; Bolton, S. (65th Annual Western Snow Conference, 1997)
To quantify the hydrologic response of forest harvesting, measurements of snow accumulation, melt, and micro-meteorological were taken in mature and harvested units of the Gifford Pinchot (GP) and Umpqua National Forests. Data were collected as part of the Demonstration of Ecosystem Management Options (DEMO) project. The study areas are located in the transient snow zone of the western Cascades of southwestern Washington and central Oregon, respectively. The GP site contains six units at approximately 900 meters in elevation (five mature secondary growth, 1 clear-cut). The Umpqua site contains five units at approximately 900 meters in elevation (four mature, one shelterwood), and three units at 1200 meters elevation, (two mature, one shelterwood). Data have been collected during the past three snow seasons. In the summer of 1997, each site's mature stands (excluding one control) will be harvested with varying retentions and additional seasons of data will be collected. Measurements of incoming and reflected shortwave radiation, incoming longwave radiation, windspeed, relative humidity, air temperature, and precipitation (or throughfall) were taken in the units. Snow accumulation and melt at the unit scale (10ha) was measured weekly throughout the winter and spring with snow courses taken on a twenty point grid. Point observations of snow pack outflow consisted of two non-weighing snow lysimeters (2.6 sq. m. each) in each unit. Comparison of lysimeter observations between shelterwood and mature units during the 95/96 season show a 56% increase in 3 day production of runoff and a greater than 150% increase in 3 day snowmelt (outflow-throughfall). The shelterwood also shows nearly a 50% increase in snowmelt during radiationdominated spring events. Snow course data taken at the GP before and 10 days after the rain-on-snow event of February 1996 show a decrease in the average snow water equivalent of the clearcut unit from 26 to 16 cm and a decrease in an adjacent mature stand's SWE from 21 to 18 cm.
Keywords: Gifford Pinchot Forest, Umpqua National Forest

1996 Title, Contents, and Minutes (64th Annual Western Snow Conference, 1996)

The effect of a canopy on the snowmelt energy balance - Adams, R.S.; Spittlehouse, D.L.; Winkler, R.D. (64th Annual Western Snow Conference, 1996)
Energy balances over snow in a clearcut, an adjacent mature Engelmann spruce-subalpine fir forest, and a thinned and pruned juvenile lodgepole pine stand are presented. Net irradiance, soil heat flux density, and heat storage within the pack, were combined with eddy correlation measurements of sensible and latent heat flux density to estimate the energy available for snowmelt. When the ripe snow packs were melting, latent and soil heat flux density, and heat storage were negligible. A highly stable lower atmosphere resulted in low sensible heat flux densities. Although distinct differences in magnitude were observed between sites, net irradiance was the largest energy source for snowmelt at all three sites. Daily snowmelt calculated from energy balance measurements agreed well with measurements from snowmelt lysimeters.
Keywords: Clearcut, Eddy correlation, Energy balance, Engelmann Spruce, Lodgepole Pine; Subalpine fir

How ocean circulation, hurricanes and the sea surfacetemperatures willaffect the precipitation in the Pacific Northwest over the next 10-20 years - R Allerman (64th Annual Western Snow Conference, 1996)
The 1994 floods in Africa, the extreme tropical storm and hurricane season in 1995 and the 1996 flooding in the Pacific Northwest seem to be unrelated events, but are they? Actually all of these events can be linked to oceanic circulation and in particular the conveyor belt theory. This theory states that ocean circulation moves warm and cold water around the globe at different speeds in decadal timescale. The Southern Oscillation Index (SOl) is also influenced by the Conveyor Belt Theory (CBT) .Furthermore, precipitation amounts in the Pacific Northwest correlate with the different phases of the SOl. It appears we are coming out of a long period of weak oceanic circulation and into anew stronger phase. This new phase will likely increase precipitation amounts in the Pacific Northwest.
Keywords: Conveyer belt, El Nino, La Nina, Ocean circulation

The effect of ski run cutting and artificial showmaking on snow water accumulation at Big Sky Ski area, Montana - Birkland, K.W. (64th Annual Western Snow Conference, 1996)
This study examines the effect of forest clearing for ski runs and artificial snowmaking on snow water accumulation at of Big Sky recreation area in southwest Montana. Extensive research shows that clearing the forest canopy for timber harvest increases water stored in the snowpack, but no studies have compared water stored in the compacted, skied, and machine groomed snowpack of ski runs with the water stored under the natural forest canopy. Thirty six sampling locations were selected, terrain variables (elevation, aspect and slope angle) were surveyed, and snow depth, density and water equivalence were measured both under the forest canopy and on the adjacent ski run. Additionally, some of the sampling locations were in areas with artificial snowmaking. Snowpack on the run has a higher density and water equivalence, and a similar depth, to snow off the ski runs. Elevation is the primary terrain variable that affects snowpack characteristics, and increases in snow water equivalence (SWE) with increasing elevation are similar to previously published research. There was no significant difference between snow water storage on ski runs with snowmaking and those without snowmaking, although the snow density on the runs with artificial snow was higher. Total increase in snowpack water storage for all ski runs at Big Sky was greater than 700,000 m3. This number is close enough to values derived from a model designed to measure water yield due to forest cutting that it appears that the clearing of ski runs causes similar increases in snowpack water storage and water yield as forest clearing for timber harvests.
Keywords: Artificial snow making, Montana, Ski runs

When NWSRFS, SEUS, and snow intersect - Bissell, V.C. (64th Annual Western Snow Conference, 1996)
The National Weather Service River Forecast System (NWSRFS) is being implemented for river and water supply forecasting operations by the National Weather Service in the Pacific northwest. The initial process of calibration has been performed only by optimizing on the observed streamflow rather than on snow observations. The Snow Estimation and Updating System (SEUS) is a postprocessor which permits snow observations to be incorporated to update model states as the season progresses. The applicability of the NWSRFS suite of programs for water supply forecasting will be impacted by (1) reliability of data observations, (2) the cognitive value of the snow and soil moisture accounting conceptualizations, (3) the effect of daily operational changes ('modifications') made to the model to keep it tracking observed st;reamflow, and (4) the 'connectivity' between SEUS and the realism with which the snow simulation duplicates reality. An example of Dworshak Reservoir (Idaho) inflow forecasts suggests thetechnique is very promising despite difficulties.
Keywords: Forecasting, Modeling, NWSRFS

Improving the accuracy of covariance estimates used in spatial modeling and estimation of snow water equivalent - Carroll, S.S. (64th Annual Western Snow Conference, 1996)
With the increasing demand for water in the United States, it is essential that water resources be accurately monitored to insure that the avajlable water supply is used optimally. Hence, the National Weather Service (NWS) maintains a set of conceptual, continuous, hydrologic simulation models to generate extended streamflow predictions, water supply outlooks, and flood forecasts for river systems throughout the U.S. The accuracy of these forecasts is very dependent on the accuracy of snow water equivalent estimates simulated by the models. Hence, periodically throughout the snow season, the simulated snow water equivalent estimates are updated using snow water equivalent estimates obtained from snow data collected in river basins around the country. The estimates are obtained using a geostatistical model and snow course, SNOTEL, and airborne snow data. In this research, we exa.Inine ways to improve the accuracy of spatial covariance estimates that are necessary to obtain snow water equivalent estimates used to update the snow simulation models. We illustrate our methodology using snow data collected in the North Fork Clearwater River basin in Idaho.
Keywords: Geostatistics, Kriging, Spatial Prediction

Snowmelt characteristics under various conditions - Cooley, K.R. (64th Annual Western Snow Conference, 1996)
Snowmelt rates vary in timing and magnitude depending on a number of factors. Snowmelt models attempt to simulate the snowmelt process based on meteorological factors, but very few actual . measurements are available for validation purposes. This paper summarizes actual daily snowmelt data and compares the results to values reported in the literature.
Keywords: Snowmelt data

Snow depth variability in a small alpine watershed - Ingersoll, G. P.; Campbell, D.H.; Spahr, N.E. (64th Annual Western Snow Conference, 1996)
The effects of mountainous topography and wind result in widely variable snow depths in alpine basins. High variance among measured snow depths and limited accessibility in alpine watersheds complicates estimation of snowpack water equivalent (SWE). Snow surveys at eight snowcourses were used in a water balance calculation for 1994 in the Andrews Creek Basin {drainage area of 183 hectares), Colorado. A mean snow depth from a single snowcourse in a forested area was compared to mean depths at seven additional snowcourses representing a variety of terrain around the watershed. The mean snow depth from the single snowcourse differed statistically from the other mean depths and underestimated the average snow depth, estimated by all eight snowcourses, by 1.2 meters. A water-balance calculation (comparing annual precipitation to measured runoff) indicated an estimated mean snow depth for the basin was substantially better when based on several snowcourses covering a range of conditions, rather than based on only one snowcourse.
Keywords: Andrews Creek Basin, Colorado, Snow depth

Research at the Central Sierra Snow Laboratory: History and hope - Kattelmann, R.C.; Osterhuber, R.J.; McGurk, B.J.; Berg, N.H. (64th Annual Western Snow Conference, 1996)
Snow studies on Donner Summit began in 1879 with the practical concerns of the Southern Pacific Railroad. Scientific work in the area was initiated by James Church to complement his research on Mt. Rose. Following World War Two, the Cooperative Snow Investigations of the U.S. Army Corps of Engineers and then-Weather Bureau chose Donner Summit as one of their 'snow laboratories'. Between 1945 and 1952, work at the Central Sierra Snow Laboratory generated much of our fundamental knowledge about snow physics and hydrology. Continuing research by the U.S. Forest Service and many cooperating agencies improved our understanding of forest-snow interactions, snow chemistry, physics ofwet snow, snowmelt modeling, and mountain climatology. The facility and its parent research program have lost funding for fiscal year 1996 and beyond. The current status of the transfer of the Snow Lab to the University of California's Natural Reserve System is discussed.
Keywords: CSSL, History, Mt. Rose, Review

Snowmelt contributions to flooding in the American River Basin - Kattelmann, R.C. (64th Annual Western Snow Conference, 1996)
Flooding during the winter of 1995 in the Sacramento area again raised concerns among residents, agencies, and politicians about safety and protection from floods of the American River for California's capital and suburbs. Mechanical failure of a principal gate on the Folsom Dam above the city during the summer of 1995 also raised concerns about the safety of structural protection against floods. A National Research Council panel released its evaluation of flood risk in the American River basin in late summer. In November 1995, the Sacramento Area Flood Control Agency recommended construction of a flood-control-only dam near Auburn. Snow has a fundamental role in the hydrology of the American River basin and can contribute large amounts of runoff to peak flows during warm storms. Snow at low elevations that subsequently melted appears to have been a critical factor in the flood of record in 1862 and the massive floods of February 1986.
Keywords: American River, Folsom Dam, Sacramento, Snowmelt

Applying the National Weather Service River Forecast System (NWSRFS) interactive forecast program to basins in Northwest Washington - Laurine, D.; Hughes, S.; Younger, M.; Orwig, C. (64th Annual Western Snow Conference, 1996)
The Northwest River Forecast Center has, during the past year, completed calibrating the National Weather Service River Forecast (NWSRFS) model in Northwest Washington. The next step in the process was to set the calibrated river basins up for the Interactive Forecast Program (IFP). This task requires defining headwater basins, routing reaches, reservoirs and downstream forecast points in the manner IFP demands. The IFP was run real-time during the 1995-96 winter forecast season. This paper will summarize the results of the model application in a complicated rain on snow environment. We will also present model enhancements resultant from this real-time test of the IFP .
Keywords: Forecasting, Models, NWSRFS

Northern Sierra snow of '83 and '95 'a comparison' - Marron, J.K. (64th Annual Western Snow Conference, 1996)
The 1995 snowpack in the Sierra changed dramatically during the year and ended with one of the highest years on record. Much to the chagrin of those hearty surveyors who sampled snow during the winter of '83 the newer samplers began claiming that the winter of '95 was much worse and the sampling of course was the hardest and deepest ever. This paper will compare the winter of '95 and the winter of '83 in two ways. The first will be to use the reported averages of each of the snow courses and secondly the amount of snow removed from the snowpack on the survey. These two analyses will provide information on me resulting snowpack and the difficulty in obtaining the measurements
Keywords: Snow survey

Use of geology in NWSRFS calibrations; Nisqually River, Mt. Ranier, Washington - Martin, K. (64th Annual Western Snow Conference, 1996)
Subsurface geology, rock types, and glacial processes greatly influence hydrogeologic processes. Good geologic understanding can create better insights for the initial estimation and subsequent adjustment of parametersof the Sacramento Soil Moisture Accounting (SAC-SMA) and SNOW-17 models of the National Weather Service's River Forecast System (NWSRFS). Geologic information is readily available from the Roadside Geology series or US Geological Survey Geologic maps.The Nisqually River near National, Washington, is divided into four areas in NWSRFS. The Lower area, filled by glaciofluvial sediments, displays a subdued hydrologic response. This geological information translates as deep SAC-SMA tension-water and free-water parameter boxes which indicate high porosity and permeability, plus significant baseflow; low SAC-SMA REXP and ZPERC values suggest rapid percolation; and low SAC-SMA UZK values mean slow recessions. The Middle and Upper areas feature massive volcanic flows which are hydrologically flashy.The Glacial area shows a glacial peak flow by August. SNOW-17 model parameters show a glacier covering 40% of a volcanic terrain. The NWSRFS Water Balance operation incorporates mass balance analyses (eg., Accumulation Area Ratio) showing glacial growth or recession. The Nisqually glacier shows a 3% decline.
Keywords: Models, NWSRFS, Soil Moisture

Measuring winter precipitation with an antifreeze-based tipping bucket system - McCaughey, W.W.; Farnes, P.E. (64th Annual Western Snow Conference, 1996)
The objective of this study was to determine if a modified storage gage charged with antifreeze and attached to a tipping bucket recorder would continuously and accurately measure winter precipitation. Precipitation measured in eight tipping bucket/storage gage (TIPSTOR) recorders were compared to measurements from eight paired snow boards, two storage gages and two weighing precipitation gages. The average total accumulation for six TIPSTORs (83.8 mm) was greater than storage gages (75.7 mm) but less than adjusted snow board and weighing precipitation gage measurements (85.6 mm and 89.3 mm, respectively) These results indicate that reasonable accuracy can be expected from the TIPSTOR. The design of the gages and the results of field tests are presented.
Keywords: Snow gage, Storage gages, Tipping bucket

Early flood warning: Forecasting the Pacific Northwest - Pattee, S.; Kammereck, A. (64th Annual Western Snow Conference, 1996)
The idea of being able to forecast the intensity of floods in the Pacific Northwest has been a dream for many years. Just thnk of the potential. Cities could be evacuated, property could be protected, livestock removed, roads blocke, sandbags placed, and most importantly -- lives saved.As like pioneers crossing the Cascade Mountains in the 1800's, Whatcom County has revolutionized the concept of early flooe warning for the Pacific Northwest. A concept that has been used in other locations such as California and British Columbia has been built unon and expanded into a complete system.
Keywords: EFWS, HYDROMET, SNOTEL

3-D Characterization of snow crystals utilizing low temperature scanning electron microscopy - Rango, A. (64th Annual Western Snow Conference, 1996)
The two dimensional shapes of snow crystals have been previously studied and photographed with light microscopes and cameras. Past investigators have been hampered by sublimation and melting of the snow crystal sample and by the limited resolution of the instruments. Better methods for measuring snow crystals are needed for understanding snowpack processes and improving microwave remote sensing of snow. Snow samples from Maryland, West Virginia, Colorado, wyoming, and Alaska have been examined with low temperature scanning electron microscopy (SEM) to produce startling new images of snow crystals. Low temperature SEM avoids problems with sublimation and melting, provides extreme magnification capability, and allows quantitative measurement of snow crystal size and shape with the assistance of 3-D or stereo imaging. The 3-D representations show in stereo several different types of newly fallen or precipitated snow crystals, numerous examples of crystals in different stages of metamorphism from natural snowpacks, and algae and bacterial forms present in a melting snowpack. The techniques for sampling, storing, and transporting snow crystals to the SEM facility are simple and easy to use.
Keywords: 3-D, Electron microscopy, Snow crystals

Spatial variance of snowmelt as a continental alpine site - Rikkers, M.; Williams, M.W.; Sommerfeld, R. (64th Annual Western Snow Conference, 1996)
We evaluated the spatial variance of snowmelt discharge during the 1995 melt season. We tested two hypotheses at Niwot Ridge, a continental alpine site located in the Colorado Front Range at an elevation of 3500 m: 1) meltwater discharge through snow is positively correlated at the scale of approximately 5 m, and 2) this characteristic lag distance will increase with time throughout the snowmelt season. In 1994, 16 small snowmelt lysimeters (each 0.2 m2 in area) were placed in a circular array with a 5 m radius; lysimeters were separated by a distance of 2 m along the circumference of the circle and drained by gravity into dedicated tip- ping buckets housed in a subnivean laboratory .The spatial variability in meltwater flux was large, with three tipping buckets over-topped during most of the snowmelt season, three tipping buckets receiving less than 5% of measured snow-water equivalence (SWE), and the remainder of the lysimeters showing a strong diurnal hydrograph. Not all hydrographs returned to near zero at night, in part because of a positive sensible heat flux. Analysis of the spatial variability of meltwater flux using geostatistics show positive correlations at distances of less than 6.5 m for the entire snowmelt cycle. This characteristic distance increased throughout most of the snowmelt season, from 2 mat the beginning of melt to 10 mat the end of the season.
Keywords: Colorado, Lysimeters, Niwot Ridge, Subnivean

Hydrologic roles of snow avalanches in high-mountain environments: A review - de Scally, F.A. (64th Annual Western Snow Conference, 1996)
The hydrologic roles of snow avalanches in high-mountain environments are rarely addressed by the research community. Yet, as a component within the snow and ice subsystem of the hydrologic cascade, avalanches can provide a significant source of accumulation for glaciers; alter the nature and timing of seasonal snowmelt; disturb the winter runoff regime through damming of rivers and displacement of lake water; and increase the incidence of other mass movement processes by their disruption of slope sediments. The purpose of this paper is to review the current state of knowledge with respect to these roles, particularly as they affect downstream hydrologic processes.
Keywords: Disturbance, Review, Snow avalanches

Temperature moistureg/soil temperature monitoring network pilot project - Schaefer, G.L.; Schilling, D. (64th Annual Western Snow Conference, 1996)
The problem exists that no national coordinated system is available to collect, interpret, and archive the atmospheric and soil climatic data required for global change and natural resource assessment, analysis and research. Baseline information is critically needed for research into these areas and to begin the process of obtaining historical information which is required to make better resource management decisions. As a result of this problem, the Natural Resources Conservation Service (NRCS), Resoures Inventory and Geographical Information System Division (RIGIS), formerly the Resources Inventory Division (RID), which has the responsibility for monitoring and conducting a Natural Resources Inventory (NRI) for accessing short term natural phenomenon, and development of national trends collaborated with the Soils Division in 1990 and established a Soil Moisture/Soil Temperature (SM/ST) Pilot Project (formerly called Global Climate Change Pilot Project). Twenty-one sites have been established in nineteen states across the United States. These sites have been operating since 1992.
Keywords: Pilot project, Soil moisture, Soil temperature

Application of principal components regression to streamflow forecasting - Smith, S.; Weiss, E. (64th Annual Western Snow Conference, 1996)
B.C. Hydro adapted the techniques of principal component regression, cross-validation and a systematic search for optimal combinations of variables (Garen, 1993), to try to improve to the statistical accuracy of stream- flow volume forecast equations for the glaciated Bridge River basin in British Columbia. The paper will discuss the trade-offs that B.C. Hydro made in balancing the improvements in forecast accuracy using these techniques against other factors, such as preserving continuity in forecast equation structure from month to month, preferring short-term stations located within the basin to longer term stations outside the basin, and using the thirty-year normals period ( 1961-90) versus the historical period of record. Results for the Bridge River system demonstrate the balance that can be achieved between optimizing forecast accuracy and selecting variables and stations which make the forecast equations more physically rational.
Keywords: Forecasting, Regression, Statistical analysis

Record estimation and extension for precipitation data - Smith, S. E.; Weiss, Eric (64th Annual Western Snow Conference, 1996)
The desire to use data from climate stations installed in the 1980's for streamflow volume regression equations required an estimating procedure to fill in missing data and extend the records back to 1961 to create a complete 30 year record. The past success of using organic regression MOVE 1 and MOVE 2 procedures in extending streamflow records (Hirsch, 1982; Alley and Burns, 1983) led to the development of a similar application for precipitation data. AMOVE 2 estimation procedure was developed for monthly precipitation data which uses : maintenance of variance techniques to minimize variance bias, and preserves seasonal variation in precipitation. Results using this procedure to estimate precipitation for climate stations located in the Bridge River system in British Columbia are presented and compared to estimates made using simple linear regression.
Keywords: Estimating data, Extending records, Modeling, Regression

Forest canopy effects on sample size requirements in snow accumulation and melt comparisons - Spittlehouse, D.L. (64th Annual Western Snow Conference, 1996)
Forest management regulations in British Columbia attempt to minimise changes in the hydrologic regime by limiting the extent of forest removal. Considerable effort is currently being focused on the quantification of snow pack differences between a variety of forest treatments and stand types. This paper assesses what size of difference can reliably be detected by the methodologies used in these studies. We examine the sample sizes required to detect specified differences in April 1 st. snow water equivalent and in the average melt rates resulting from harvesting an Engelmann spruce -subalpine fir forest. Snow water equivalent was measured at 64 points in a clearcut, in thinned and unthinned juvenile pine stands, and in a mature forest. A power analysis was used to determine sample sizes necessary to detect specified differences. The standard 10 point sampling approach was found to be adequate to detect differences of greater than 6 cm in snow water equivalent, and 1 cm d-l in the mean daily snowmelt rate calculated over a six day period, for a= 0.05 (Type I error) and power = 0.9 (Type n error). Increasing sample size to 30 points substantially decreased the size of the difference in snow water equivalent that could be reliably measured. However, 50 samples were required to determine differences in melt rate between the forest and clearcut of 0.5 mm d-l.
Keywords: British Columbia, Clear cutting, Forest management

Can livestock producers manage snow to grow more alfalfa in dryland watersheds? - Steppuhn, H.; Wall, K.G (64th Annual Western Snow Conference, 1996)
Double rows of tall wheatgrass (ThinoDvrum Donticum), spaced on 15.2-m centers, have been recommended as vegetative windbreaks designed to enhance snowcovers and moderate growing-season evapotranspiration on the northern Great Plains and the Canadian Prairies. Such a windbreak system along with an adjacent open area on non-irrigated land near Swift Current, Saskatchewan, was seeded to three alfalfa varieties (Rangelander, Beaver and Angus) in 1986. Snowcover water equivalents, spring soil water contents, alfalfa water consumption, and forage production in all three varieties, observed over seven years, were significantly greater in the windbreak shelter than in the open field. The over-winter recharge of water in the upper 120 cm of soil averaged 22 mm (78%) greater behind the windbreaks than in the open. This extra water contributed to a 40% increase in mean annual forage yield from 1610 to 2250 kg ha-l.
Keywords: Alfalfa, Livestock, Wheatgrass

Effects of microalgal blooms on Sierra Nevada snow albedo - Thomas, W.H.; Duval, Brian (64th Annual Western Snow Conference, 1996)
Initial (1993) investigations of snow albedo and snow color (caused by algae) in the Sierra Nevada of California showed that albedo was reduced in red snow patches as compared with that in white snow patches. In May-June, 1994, extensive concurrent measurements of snow albedo, snow algae numbers, and snow water content were made in the Tioga Pass area (upper Lee Vining Creek watershed) of the range. Statistically significant negative correlations were found between albedo and algal cell numbers and water content. However, red snow did not decrease mean albedos in large representative snowfields that contained algae. This was due to the patchiness of the algae, and mean albedos probably would not decrease because of algae over the whole Lee Vining Creek watershed. Thus water supply from melting snow would not be affected by the presence of algae. Especially in the early algal season, dirt, as well as algae, contributed to decreases in albedo.
Keywords: Albedo, Algae, Red snow

Snowmelt at the high Arctic sites, Resolute, N.W.T. - Yang, D. (64th Annual Western Snow Conference, 1996)
To understand the snowmelt processes in the high Arctic, field work was conducted during late May to mid June of 1994 at two sites in the study area near Resolute, Cornwallis Island. One site had relatively clean snow and the other was covered by windblown dust from the road and runway nearby. Microclimate elements (air temperature, precipitation, humidity, windspeed, radiation) and snow temperature and daily snow melt were recorded by automatic instruments at both sites. Snow samples were collected at fixed locations on selected dates for dust content analysis. Comparison of the microclimate was made between the sites and significant difference of dust content, of snow surface albedo and, hence, of net radiation was found. As result of the radiation difference, the dirty snow melted earlier and the snow cover disappeared about 10 days before the clean snow.In the calculation of energy balance, snow surface roughness length was estimated by wind profile method using wind observations at 3 levels at the site. The comparison of snowmelt computed from the energy balance was made to the observed snowmelt in the field. A good agreement has been obtained at two sites with different snow conditions. This indicates that the energy balance approach is a good short-term predictor of snowmelt in the high Arctic.
Keywords: Arctic, Microclimate, Modeling, North West Territories, Snow accumulation

Snow accumulation patterns in Idaho - Zhaoxing, L.; Morris, S.; Chang, K-T. (64th Annual Western Snow Conference, 1996)
We obtained snow course data from 230 stations in Idaho and western Montana, and our research focused on the transformation of these point data to a statistical surface so that the data could be better utilized for water resources applications. The transformation question was approached at two levels. At the first level, we used the snow course data directly with different spatial interpolation algorithms including the inverse distance squared and universal kriging methods. The first approach yields poor results because of the non-random, non-regular spatial sampling that the snow courses represent. At the second level, we used a geographic information system (GIS) to collect several layers of information such as elevation, slope, and aspect and built a regression model to predict monthly SWE values for the Idaho snow courses. These models are formulated at the watershed scale, and generally yield very good results (R2 = 0.70 -0.98). The regression models were then employed to build a denser network of points for spatial interpolation. Future research will examine the reliability andutility of these 'snopographic' surfaces.
Keywords: GIS, Montana, Snow course, Statistical surface

1995 Title, Contents, and Minutes (63rd Annual Western Snow Conference, 1995)

Comparing differences in mountain and valley precipitation networks in Lake County, Oregon - Allerman, Rob; Swanson, R.H. (63rd Annual Western Snow Conference, 1995)
Precipitation sites in Lake County, Oregon, include mountain (Snow-Telemetered Network) and valley (Cooperative Observers Network) locations. Often times the percent of monthly totals for these two networks are published separately due to the equal importance these networks have in determining stream flow forecasts and water supply. Simple linear regression equations comparing monthly precipitation and adjacent streamflow totals show this to be the case.
Keywords: Precipitation networks

Updating seasonal snowmelt estimates using snowcourse measurements - Assaf, H.; Loukas, A.; Quick, M. (63rd Annual Western Snow Conference, 1995)
In mountainous watersheds, like those of British Columbia and northern Pakistan, rivers are mainly fed by snowmelt from winter-accumulated snowpack and glaciers. For a safe and optimal operation of reservoirs fed by these watersheds, it is important to obtain reliable estimates of the volume and time distribution of seasonal snowmelt.An iterative procedure has been developed to utilize snow course measurements to update estimates of snowfall contribution to the watershed. Consequently snowpack volume available for melting is modified and seasonal forecasts are adjusted accordingly.The updating scheme has been applied to the snowpack measured at Mount Fidelity in the Upper Columbia River Basin in British Columbia. The results showed great improvements is streamflow forecasts, particularly during the critical melting season.
Keywords: Snow courses, Streamflow forecasting

Dependence of ground snow loads on elevation in western Canada - Auld, H. (63rd Annual Western Snow Conference, 1995)
Provincial and territorial snow course measurements and the Atmospheric Environment Service (AES) snow depth measurements were combined and analyzed using Geographical Information System (GIS) software to study the spatial variation of design Ground Snow Loads in mountainous areas of western Canada. With careful attention to mesoscale climate processes, physical models were developed that described the regional variation of snow loads with elevation dependency for regions of homogeneous snow climatology. Valley and mountain range specific regression relations were derived that were used to normalize return period snow observations with respect to critical or reference elevations. Interpolation procedures were applied to determine site specific or grid point snow loads. Further work is needed to better quantify uncertainties associated with the snow fields and snow data. The results of the study provided an improved methodology for determining Ground Snow Load recommendations supporting the National Building Code of Canada in mountainous areas.
Keywords: GIS, Snow loading, Spatial variation

Calibration of the NWS model in the Northwest: a status report - Bissell, V.C.; Orwig, C.E. (63rd Annual Western Snow Conference, 1995)
The Northwest River Forecast Center has been using the SSARR model for four decades to forecast streamflows in the Columbia River and western Oregon and Washington basins. A major effort is now underway to calibrate Pacific Northwest basins with the National Weather Service River Forecast System (NWSRFS) model, including the NWSRFS snow model. Staff of the NWFRC have calibrated more than half of the basins of northwestern Washington, and should have all of western Washington finished by fall 1995. Calibrations must address both the winter flood forecast season and the spring snowmelt season (emphasis on both floods and multi-purpose water management). Some parameters, such as seasonal melt rated, reflect unique Pacific Northwest climatology. In the Columbia River Basin, many calibrations have been done for the Bonneville Power Administration (BPA) by a private contractor, and those results will be available for use by the NWS.
Keywords: Flood forecasting, Models

Quantifying runoff rights to cloud seeding augmented snowfall: the ASCE model state water code - Davis, R.J. (63rd Annual Western Snow Conference, 1995)
Snowpack augmentation by cloud seeding is sponsored by organizations seeking to increase runoff. If they wish to obtain prior right to use such increased runoff as against other claimants to the water, they must follow state water rights allocation laws. A few weather modification liability claims cases suggest that persons developing water through weather modification may have a legal right to such augmented streamflow. Additionally a few states provide by statute for water rights to added runoff. But as yet there is no case or statutory law addressing the manner in which the quantity of such water is determined. The recently completed American Society of Civil Engineers Model State Water Rights Codes have established water rights quantification mechanisms. Using techniques of hydrology, meteorology, and civil engineering, water rights claimants under the codes would provide data from a statutory list of relevant factors to state water resources allocation decision makers so they can determine the extent and priority of the augmented water supply and officially recognize a right for that amount of water.
Keywords: Cloud seeding, Legal rights, Water rights, Weather modification

Monitoring snowpack ablation using lysimetry or, sublimation - a forgotten concept in the snow managers' toolbox - Dexter, L.R.; Avery, C.C.; Delinger, W.G. (63rd Annual Western Snow Conference, 1995)
Lysimetry was used to measure sublimation from snow in a field and laboratory study. Sites sheltered from clear sky exposure lose more water to sublimation and exposed sites lose more water to melt.
Keywords: Ablation, Sublimation

Evaluation of forest fire effects on snowpack accumulation and melt - Dodd, B.N.; Molnau, M.; Robichaud, P.; Belt, G. (63rd Annual Western Snow Conference, 1995)
In July of 1991 a fire swept through the Fourth of July Creek drainage in northwestern Montana. This area has a history of rain-on-snow events producing very high runoff and severely damaging streams. This study was set up to study the effects of fire severity on the delivery of snowmelt water to the soil.Snowmelt lysimeters were set up under four conditions a clearcut open site, a very heavily fire damaged site with a few snags left standing, an area of light burn damage and an undisturbed area that had not been logged since at least the 1920’s. Two lysimeters were installed in each treatment in the summer of 1993.Both snowmelt rates and volumes were compared for both snowmelt and rain-on-snow events. Usable data were collected in March and April.Overstory and basal area reduction due to fire or timber removal will increase mean air temperature while it decreases precipitation amount reaching the forest floor.Different meteorological events caused melt rates and volumes to be different for the different canopy overstory amounts.
Keywords: Fire, Lysimeter, Rain-on-snow

Estimating monthly distribution of average annual precipitation in mountainout areas of Montana - Farnes, P.E. (63rd Annual Western Snow Conference, 1995)
Many computerized models and Geographic Information Systems (GIS) are being used to estimate average annual precipitation in mountains of the western United States. In most areas, there is a good correlation between average annual precipitation and elevation and most models use elevation to distribute annual precipitation to unmeasured areas. There is an increasing need to distribute these annual values to monthly averages. Some models use elevation to distribute monthly precipitation. Some models use the monthly distribution for long-term valley stations to distribute annual precipitation in higher elevations. Studies in Montana show there is a significantly different distribution of monthly precipitation between valley and mountain areas, particularly in the winter and spring months. Comparisons for some watersheds in Montana are shown and proposed procedure for distributing annual precipitation into realistic monthly increments is presented.
Keywords: GIS, Lapse rate, Models, Precipitation distribution

A long term winter orographic cloud seeding program conducted in central and southern Utah - Griffith, D.A.; Thompson, J.R.; Risch, D.A. (63rd Annual Western Snow Conference, 1995)
North American Weather Consultants (NAWC), a subsidiary of the TRC Environmental Corporation, has conducted a wintertime cloud seeding program in Utah during most years since 1973-74. The goal of this program has been to augment the snowfall in the mountainous regions in central and southern Utah. Additional surface runoff that results from this program is utilized primarily for irrigation of farm lands during the summer months.This program relies primarily upon a network of ground based silver iodide generators sited upwind of the mountain barriers. Seeding operations are directed from a central forecast facility in Salt Lake City.An evaluation of this program has been based upon high elevation precipitation and snowpack measurements. A target/control regression prediction analysis based on these measurements indicate approximately a 15 percent increase in precipitation over the target area for the seeded seasons.
Keywords: Cloud seeding, Evaluations, Weather modification

Operational processing of multi-source snow data - Hartman, R.K.; Rost, A.A.; Anderson, D.M. (63rd Annual Western Snow Conference, 1995)
Near real-time quantitative assessments of areal extent of snow cover and snow water equivalent (SWE) provide valuable insight and information for water management, hydrologic forecasting, and emergency preparedness entities throughout the United States and Canada. Since 1986, the National Operational Hydrologic Remote Sensing Center (NOHRSC) of the National Weather Service (NWS) has provided these data in rasters and alphanumeric tabulations generated using satellite image processing, spatial interpolation, and GIS analysis.Composite use of multi-source satellite (i.e., Advanced Very High Resolution Radiometer (AVHRR) and Geostationary Operational Environmental Satellite (GEOS), point (i.e., manual and telemetered observations), and line (i.e., airborne gamma radiation surveys) data is now accomplished through the newly developed NOHRSC Operational Product Processing System (OPPS). OPPS ingests and databases classified (i.e., snow, ground, cloud, and unknown) satellite areal extent of snow cover rasters and all identified point and line samples of SWE and snow depth. OPPS generative capabilities include user prioritized composite raster generation and multi-source gridded estimates of SWE and snow depth. OPPS spatial estimation processes for SWE and snow depth combine point and line data with composited satellite areal extent of snow cover rasters. OPPS can 1) output rasters in any of several common GIS formats, 2) create displayable images with user-defined vector overlays, and 3) integrate raster data within basin boundaries to produce alphanumeric data products. OPPS products can be stored and distributed using the NOHRSC electronic bulletin board system, FTP’d over Internet to interested cooperators, and sent to NWS offices over AFOS.
Keywords: GIS, Internet, Satellites, Snow cover

Benefits from historic cloud seeding programs in California - Henderson, T.J. (63rd Annual Western Snow Conference, 1995)
California has the longest history of operational cloud seeding programs of any area in the world. The technology was first applied by the California Electric Power Company (now Southern California Edison Co.) beginning on February 2, 1948 over the Bishop Creek watershed in the eastern Sierra. Within the next few years additional programs evolved over watersheds of the San Joaquin, Kings, Mokelumne, and Feather Rivers. As the years evolved, additional programs were initiated over other areas of California as funded by county water agencies, municipalities and hydroelectric interests. During the 1994/95 winter season a total of 15 operational programs were active. Evaluations of several cloud seeding programs in California have been extensive. In addition to serious statistical methods applied to precipitation and streamflow data, these evaluations have more recently focused on extensive radar data collected by operational 3 cm and 5 cm weather radar systems. The combined benefits are explored from ten programs in California which have been active for various periods since 1950.
Keywords: Cloud seeding, Statistical evaluations, Weather modification

Tree rows for snow accumulation in stock ponds - Jairell, R.L.; Schmidt, R.A. (63rd Annual Western Snow Conference, 1995)
This paper presents results of small scale model experiments to determine optimum location of tree rows for increasing snowdrift volumes in pit reservoirs. These small scale model studies suggest that when a tree row is used to accumulate snow in a pit reservoir, the only effective location as at the upwind edge of the pit. Trees will draw water from the reservoir, reducing the volume available for other uses. However, amounts are of the same order as evaporation rates, and are likely to be less than seepage losses, unless the pit is lined. Low-use evergreen species reduce this water use to approximately half the amount required by cottonwood, poplar or willow. The benefits of vegetative barriers – as wildlife habitat, for example—may offset the difficulties of establishing and maintaining a living barrier.
Keywords: Living barriers, Scale models, Snow drifting, Snow fences

Snow hydrology in watershed analysis - Kattelmann, R.C. (63rd Annual Western Snow Conference, 1995)
Watershed analysis refers to evolving systems of procedures for characterizing hydrologic and ecosystem processes within catchments as input to land management plans and practices. The most formalized approaches to watershed analysis were developed by the Washington Forest Practices Board and the Forest Ecosystem Management Assessment team and its successors. Watershed analysis seeks to determine critical processes and their extent, condition of the landscape and channel, impacts of past practices, location of sensitive areas, existing problems of water regime and quality, influences on aquatic habitat, and other information about watersheds relevant to resource planning and management activities. In higher-elevation basins, information about snow cover and snowmelt processes is necessary for a thorough watershed analysis. Characterization of a basin’s snow hydrology provides fundamental knowledge for understanding temporal and spatial patterns of water availability for runoff. The typical distribution of snow and related synchronization of tributary flows, alterations in snow cover from past harvesting, and potential for rain-on-snow peak flows can influence land management options.
Keywords: Ecosystem management, Planning, Watershed analysis

Continentality and the snowpack density distribution in the western United States - Kosnik, K.E. (63rd Annual Western Snow Conference, 1995)
An index of continentality is used to evaluate the distribution of snowpack density in the western United States. Continentality describes the climatic differences arising from proximity to major water bodies and from the effects of a continental land mass. The ability of maritime air masses to penetrate inland and impart a moderating effect on surface air temperature is reflected by the continentality index. Close proximity to the Pacific Ocean has the effect of providing abundant moisture for precipitation and minimizing the annual range in temperatures. The continental interior experiences an increased temperature range and a dryer climate. The dependence of snowfall and, ultimately, snowpack density on atmospheric temperature and water vapor supply, suggests a link between continentality and snowpack density. The usefulness of a continentality index to capture climate conditions relevant to snow density is evaluated.
Keywords: Climate, Indices, Snow density

Seasonal funoff forecasts for hydropower based on remote sensing - Martinec, J.; Rango, A. (63rd Annual Western Snow Conference, 1995)
In this study, the target of seasonal runoff forecasts for April through September is the inflow into the reservoir of the Swiss hydroelectric station at Sedrun and the river flow for the run-of-the-river station at Tavanasa. The catchments are situated in the Swiss Alps at 1300-3200 m a.s.l. so that snow is an important runoff factor. Snow reserves on 1 April can be reconstituted from satellite snow cover monitoring during the snowmelt period. In real time, point measurements of the snow water equivalent on 31 March serve as indices to select a snow cover of a past year evaluated from monitoring. Based on snow reserves and expected precipitation, monthly runoff volumes are forecasted on 31 March and updated after satellite overflights. Errors in 1993 and 1994 resulted from unusually warm temperatures and heavy rainfalls at the end of the snow melt season in September. More reliable forecasts improve hydropower generation and help to achieve better prices on the electricity market.
Keywords: Hydroelectric power, Remote sensing, Satellites

Preliminary information on snow interception, accumulation, and melt in northern Rocky Mountain lodgepole pine forests - McCaughey, W.W.; Hansen, K.; Farnes, P.E. (63rd Annual Western Snow Conference, 1995)
Tenderfoot Creek Experimental Forest (TCEF) is located in the Little Belt Mountains in north central Montana and was established in 1961 for watershed research. Tenderfoot Creek flows into the Smith River, a major tributary of the Missouri River. In the early 1990’s, the original watershed scope for TCEF was expanded to include studies of fire, fisheries, composition of vegetation and animal communities, and other physical, biological, and social factors as they relate to landscape-level management. Social factors relating to water resources are increasing in importance for research on TCEF. Information on snow interception, accumulation, and snow melt from mountain watersheds is important for stream flow management in the Northern Rocky Mountains such as the Smith, Missouri and upper Columbia river systems.Preliminary data on snow water equivalent (SWE) in lodgepole pine stands were measured on six paired snow courses in TCEF. Two snow pillows, one in an opening and the second in an adjacent lodgepole pine stand, were installed during the fall of 1993 and SWE was recorded, for these pillows, on continuous chart recorders during the winters of 1993/94 and 1994/95. The snow pillows are also located adjacent to an open/canopy snow course pair, at the headwaters of Tenderfoot Creek. Snow water content increased an average of 38 percent in openings over adjacent stands of lodgepole pine and ranged from 19 to 85 percent. Canopy density influenced snow accumulations and redistribution of snow from lodgepole crowns to the ground. Snow melt-out occurred approximately 2 weeks later on canopied sites than on open sites.
Keywords: Forest openings, Interception, Lodgepole pine

Implementation of the Snow Estimation and Updating System (SEUS) in the Clearwater River Basin, Idaho - McManamon, A.; Hartman, R.K.; Hills, R. (63rd Annual Western Snow Conference, 1995)
The Snow Estimation and Updating System (SEUS) was developed by the National Weather Service (NWS) to generate real-time gridded snow water equivalent estimates using ground-based and airborne snow data collected over the western United States. These gridded snow water equivalent estimates incorporate the spatial variability of the snowpack induced by orographic effects in the West. The estimates of snow water equivalent are used for hydrologic forecasting. In previous years, the SEUS has been implemented in portions of the Colorado River Basis and the results used for water supply forecasting.The 1995 snow season included some enhancements to the way the SEUS methodology was implemented to continue to improve the snow water equivalent estimates generated. Some improved data layers were added including seasonal precipitation layers developed using Precipitation-elevation Regressions on Independent Slopes Model (PRISM). This paper examines the effect of including airborne data on the snow water equivalent estimates. The impact of using satellite areal extent of snow cover to estimate the location of the snow line and its effect on the snow water equivalent is also examined. The NWS is interested in implementing the SEUS under a variety of physiographic and hydrologic regimes. The SEUS was implemented in the Clearwater River basin of Idaho where a more maritime climate provides a significant amount of moisture and where the elevations are not as extreme as they are in other portions of the Colorado Basin.
Keywords: Orographic, Satellite, Snowcover

An evaluation of research programs at the Central Sierra Snow Laboratory, 1945-1964 - Miller, D.H. (63rd Annual Western Snow Conference, 1995)
Several public agencies took part in one or another of several cooperative programs investigating problems of the snow landscapes of the Sierra, and submitted their own problems of design and reservoir operation, river forecasting, and water and sediment yields. These problems were organized into a research program essentially centered on the fact that a snow landscape is the arena of interaction between water and energy; so the fluxes in these two physical budgets outlined our task. Of the three field basins active in the Cooperative Snow Investigations, the Central Sierra Snow Laboratory (CSSL) had the most detailed field observations; and in the later Snow Management program (FS), CSSL was the site of half of the research projects in the Sierra snow zone; it was the basin with which I grew most familiar.Field observations and data analyses emphasized heat supply, characteristics of the surface of the snow, water transmission through the deeper layers, and stream flow; techniques for hydrograph reconstitution for Castle Creek were validated in operational basins like the Yuba and Kootenai Rivers. In the second program at CSSL, detailed measurements of the forest environment of each snow course gave data for analyzing the separate effects of trees on shortwave radiation, longwave radiation, shelter, and wind transport.It is interesting that the intellectual curiosity of a university professor ninety years ago led to research that produced notable scientific findings about snow cover, and to physically sound operational techniques for design floods, flood forecasting, and managing the public domain. I feel privileged to have been a part of these major research programs in the physics of this complex mountain landscape, and now appreciate the invitation to evaluate these programs from the viewpoint of my subsequent scientific career.
Keywords: Evaluations, Research programs

Graphical user interface for SNTHERM - Moffitt, J.A.; Barth, G.R. (63rd Annual Western Snow Conference, 1995)
A snowmelt modeling PC interface was developed with widely used, off-the-shelf spreadsheet and database software packages. While this application was designed for the snowmelt model SNTHERM (U.S. Army Cold Regions Research and Engineering Laboratory), the programming concepts and design were general enough to be applied to other environmental models. Extensive screen design utilities and programming capabilities make current software applications strong candidates for Graphical User Interface development.The modeling interface consisted of six major functions: (1) database query screens for plotting and exporting data, (2) automated creation of two required model input files with menu and mouse driven screens, (3) modeling file management, (4) automatic plotting of the model input and output data, (5) running SNTHERM, and (6) automated sensitivity analysis graphics of model parameters.
Keywords: Graphical user interface, Modeling

Snow plates: preliminary results - Moffitt, J.A. (63rd Annual Western Snow Conference, 1995)
This paper presents the design, construction and calibration of field instrument to measure snow water equivalence (SWE). This instrument, referred to as a ‘snow plate’, consists of a 1 sq m circular, perforated aluminum plate assembly mounted on three loadcells. When coupled with a ultrasonic snow depth sensor, measurements of snow density can be made. This plate was designed to make high frequency high resolution SWE measurements on the Front Range of Colorado. Snow events typically are temporally isolated and produce a SWE of 2 cm or less. The tested plate can measure a maximum SWE of 34.5 cm. The maximum SWE capacity can be increased by using higher capacity loadcells. A preliminary 0-4.5 SWE (0-45 kg) loading/unloading calibration test shows that the plate has an average error of 0.0284 cm SWE (0.284 kg), with a maximum error of 0.0817 cm SWE (0.817 kg) at 3 cm SWE (30 kg). Ninety-five percent of the 1210 test measurements had errors of less than 0.05 cm SWE (0.5 kg). This test indicates that the snow plate may be a useful alternative to the traditional snow pillow for measuring SWE. This instrumentation is portable, requires minimal maintenance, and may be used in dense forests and rocky and sloped terrain. The snow plate may help provide important information on the effects of topography and vegetation on snow accumulation.
Keywords: Snow gauge, Snow measurements, Snow pillow, Snow water equivalent

The recent California drought - Roos, M. (63rd Annual Western Snow Conference, 1995)
The 1987-92 drought was the worst sustained drought in history (since 1850) across central California and nearly equaled the 1929-34 drought in northern California. The six years of drought are characterized using statewide statistics on precipitation, runoff, spring snowpack, and reservoir storage. Then, the drought in the Sacramento and San Joaquin River basins is compared with other historical droughts and the droughts shown in the reconstructed runoff of the Sacramento River since the year 1960 from tree ring studies. Certain climate factors are important in understanding the drought picture for California. Some discussion of the impact on Central Valley Project and State Water Project supplies and future implications wrap up this paper.
Keywords: Dendrochronology, Droughts, Tree rings

Delaying seasonal snowmelt with avalanche activity: some results from the Cascade Mountains, southern British Columbia - de Scally, F.A. (63rd Annual Western Snow Conference, 1995)
Winter-time avalanche activity has the potential to delay a portion of annual snowmelt runoff from high elevation basins, if enough avalanche transported snow is deposited in sites where it is protected from subsequent ablation. In the Cascade Mountains of southern British Columbia, streamflow after the main snowmelt period in three years from a small (5 sq km) avalanche prone basin is substantially greater than from an adjacent forested, avalanche-free basin. The total excess of discharge over an eleven week period after the complete disappearance of undisturbed snow cover totals 80,000 cubic meters/sq km (80 mm) in 1992 and 1993, and 130,000 cubic meters/sq km (127 mm) over a thirteen week period in 1994. Despite much lighter than normal avalanche activity in all three winters, the delayed melting of avalanche show accounts for 18 to 30% of this excess and 12 to 21% of the total streamflow from the avalanche prone basin over these summer periods. Other factors which might play a role in producing these differences in basin yield are also discussed.
Keywords: Avalanches, Water supply

A bibliographic database for the Western Snow Conference - Swanson, R.H.; Richards, R.P. (63rd Annual Western Snow Conference, 1995)
The Western Snow Conference bibliographic database contains the titles, complete citations and abstracts, where available, for all articles published in the WSC proceedings since its inception in 1933. Articles may be searched by author, title, or subject keyword. Selected articles can be marked for transfer to files for later inclusion in popular word processing programs (such as MS Word, Word Perfect) or to a printer.The database requires Microsoft Windows 3.0 or later to run. It should also run under IBM OS/2 ver 2.1, Windows NT ver 3.1, or Windows 95. The database contains a runtime version of all software necessary to run it and it has been given to the Western Snow Conference for free distribution to the membership except for media, mailing and handling costs.
Keywords: Bibliography, Database

1994 Title, Contents, and Minutes (62nd Annual Western Snow Conference, 1994)

Snow chemistry and physics of the Mogollon Rim in Arizona - Barbaris, B.; Betterton, E.A. (62nd Annual Western Snow Conference, 1994)
Snowpack samples from the central mountain region of Arizona were analyzed for eleven major ions and thirty trace elements. The results indicate a relatively pristine snowpack that is weakly influenced by anthropogenic activity in most samples. Trace metals associated with human activity (Ag, As, Co, Cr, Hg, Se, Zn) were below detection limits. A pH range between 4.9 and 5.7 was measured with a mean value of 5.4, and these findings exhibit some temporal and spatial tendencies. A majority of samples had extremely low ionic strengths. The results suggest a combination of ammonium and calcium salts, sea salt, and inorganic and organic acids in the snowpack. The free proton (H+) accounted for a significant portion (32%) of the total cation availability. Meteorological influences were investigated by separating the observations by winter storm event. Samples collected on 2/4/93 exhibited a significantly greater ionic strength due to a different weather pattern during this storm. Spatial variations due to local effects were also evident in the snowpack.
Keywords: Snow chemistry, Weather patterns

Estimating the mean squared prediction error of the areal snow water equivalent estimate for a river basin - Carroll, S.S.; Carroll, T.R. (62nd Annual Western Snow Conference, 1994)
With the increased demand for water in the United States, particularly in the West, it is essential that water resources be accurately monitored. Consequently, the National Weather Service maintains a set of conceptual, continuous, hydrologic simulation models used to generate extended streamflow predictions, water supply outlooks, and flood forecasts. A vital component of the hydrologic simulation models is a snow accumulation and ablation model that uses observed temperature and precipitation data to simulate snow cover conditions. The simulated model states are updated throughout the snow season using snow water equivalent estimates obtained from airborne and ground-based snow water equivalent data. The National Weather Service has developed a spatial geostatistical model to estimate the areal snow water equivalent in a river basin. The estimates, which are obtained for various river basins in the West, are used to update the snow model. To facilitate updating of the simulated snow water equivalent estimates generated by the snow model, it is necessary to have estimates of the mean squared prediction errors of the areal snow water equivalent estimates. In this research, we derive an expression for the mean squared prediction error of the areal snow water equivalent estimate for a river basin.
Keywords: Remote sensing, Simulated models, Statistical analysis

Northern latitude snow pillow installation procedures - Clagett, G.; McClure, R. (62nd Annual Western Snow Conference, 1994)
Snow pillow installations in the sub-arctic regions of Alaska and Yukon Territoties require special procedures. A 'normal' SNOTEL-type hypalon pillow installation would not likely provide accurate data, or even survive, due to one or all of such problems as frost heaving, lack of good soil for proper bedding, and bears. These problems are adequately solved by installing the pillow on top of a treated 2x6 and plywood platform, similar to a normal house subfloor; plumbing the pillow to a wet-tolerant or 'submersible' stream gage-type transducer that is attached to the frame under the pillow so that pillow and transducer heave as a unit; and treating the hypalon pillow with a floating sheet-metal top covering and rigid bent-metal edge covering bolted to the underlying frame.
Keywords: Bears, Frost heaving, Snow pillow, Transducer

Digital photogrammetric determination of alpine snowpack distribution for hydrologic modeling - Cline, D.W. (62nd Annual Western Snow Conference, 1994)
This paper discusses progress in the use of digital photogrammetry for producing two products: 1) orthophotos, from which maps of snow-covered area (SCA) can be produced, and 2) maps of the spatial distribution of snow depth, determined by subtracting a snow-free DEM from a snow-covered DEM. SCA is commonly used by snow hydrologists for modeling and other purposes. When aerial photography is used as a source for SCA, it is important that the photography is first ortho-rectified. In this paper, it is shown how digital photogrammetry can be used to produce orthophotos on a desktop computer, using ground control obtained from maps and a digital elevation model (DEM). The digital photogrammetric determination of snow depth has proved to be a much more difficult task, and results so far have been unsuccessful. Strict requirements for ground control accuracy appear to be the major constraint for this method. A brief overview of digital photogrammetry is provided, followed by a discussion of testing results from Sky Pond, an alpine basin in Rocky Mountain National Park, Colorado.
Keywords: DEM, Digital Elevation Models, Sky Pond, Snow covered area

An automated meteorological data validation system for the Soil Conservation Service SNOTEL network - Cooley, K.R.; Palmer, P.L.; Searcy, M.L. (62nd Annual Western Snow Conference, 1994)
The SCS and ARS have collaborated on a project to develop an automated validation system for hydrometeorological data collected by the SCS SNOTEL system. The analysis portion of the software analyzes historical cata collected at individual SNOTEL sites, defining the expected ranges and daily changes of snowpack, precipitation, and air temperature data. The validation portion of the software screens real time data against these limits as well as performing other quality control tests. The implementation of this software into the SCS SNOTEL system will yield improved data quality for water supply forecasting and other resource management activities. Future planned developments include the incorporation of tests comparing data from nearby sites, and development of an algorithm for estimating missing or erroneous data.
Keywords: Data validation, Quality control, SNOTEL, Snow pillows

Climate induced change in the standard deviate of snow depth and water equivalent - Dracup, J.A.; Sample, J.P.; Wells, P.M. (62nd Annual Western Snow Conference, 1994)
Data from 72 snow courses selected through the Anglo Pacific Coast of North America were analyzed in order to document the existence of a dramatic climate induced change in the standard deviate of snow depth and water equivalent that began in 1976. Temporal and spatial comparisons were made between each of the 72 snow courses. A pronounced decrease in the standard deviate of snow depth and water equivalent was evident for the courses located throughout the Pacific Northwest. The results suggest that the step-like anomaly ended after 1987, quite possibly coincident with the end of a sustained El Niño warming trend and the return of a La Niña cooling trend resulting from the Southern Oscillation cycle in the tropical Pacific Ocean.
Keywords: Climate change, El Niño, La Niña, Snow course data

Assessment of temperature, precipitation and snow depth variations durnig the last 100 years in the former Soviet Union (FSU) - Fallot, J-M.; Barry, R.G. (62nd Annual Western Snow Conference, 1994)
A climatological study is made of regional variations in temperature, precipitation ansd snow depth observed in the FSU during the last 50 - 100 years. Analysis, methods and some results of the January trends for these 3 parameters are presented.
Keywords: Climate, Soviet Union

Modernization of statistical procedures for water supply forecasting - Hartman, R.K.; Henkel, A.F. (62nd Annual Western Snow Conference, 1994)
The promise of conceptual watershed models and extended streamflow prediction all but terminated statistical water supply forecasting technique development by the National Weather Service in the early 1980’s. Statistical procedures have, however, remained the dominant technique and will have a role when conceptual watershed models become dominant in use. Recognizing this, the Colorado Basin River Forecast Center (CBRFC) modernized its’ statistical water supply forecasting system to take advantage of current technology and resources.The system described includes a database, calibration, and operational component. The system was designed to make calibration and operational use fast, simple, and informative. System flexibility allows the hydrologic developer to structure procedures as desired using any information deemed appropriate. As such, weather indices and long range weather forecasts can be used. Application of the system significantly improved the quality of water supply forecasts issued by the CBRFC during water year 1993.
Keywords: Colorado River Basin, Conceptual watershed models, Statistical techniques

Changing the way SCS stores climatic data - Huddleston, J.M.; Marron, J.K. (62nd Annual Western Snow Conference, 1994)
The mission of the Soil Conservation Service Climate Data Access Facility is to access, obtain, evaluate, manage, and disseminate the climatic data needed to support agency programs and activities nationally. The objective is to increase efficiency and effectiveness in climatic data utilization in SCS through the use of a centralized climatic data service center. Historical climatic data obtained in 1985 has been stored online in a custom built data base in Portland. The underlying storage architecture is being replaced by netCDF, an I/O library callable from C or FORTRAN which stores and retrieves scientific data structures in self-describing, machine independent files. Using netCDF will improve the accessibility to the data for scientific data access, management, analysis and display.
Keywords: Data accessibility, Data storage, Data structures, Mission

Impact of climate change on water supply in the upper Yukon River - Janowicz, J.R.; Ford, G. (62nd Annual Western Snow Conference, 1994)
A study was carried ot to determine the impact of projected climate change on water supply in the Yukon River above Whitehorse. The system is glacier fed with peak flows in late summer. Earlier low elevation snowmelt keeps water levels high for most of the summer. Historical monthly values of temperature and precipitation were used to develop a relationship with streamflow. Changes in temperature and precipitation based on a projected 100 percent increase in CO2 were used as a starting point to assess water supply impact. Evapotranspiration rates were estimated using a method which requires readily available parameters. These values were compared with projected monthly inflows to assess climate chamge impacts on the water balance.
Keywords: Climate change, Glacier, Model

Macroscale hydrological modelling with GCM climate data - Kite, G.W. (62nd Annual Western Snow Conference, 1994)
General circulation models (GCMs) perform vertical water and energy balances at 20 or 30 minute time intervals for grid points 2-4deg apart but generally contain no information on the land-phase transfer of water between grid points or within watersheds. This study used a distributed hydrological model with data output from the Canadian Climate Centre’s GCM. A water balance was carried out at 12-hour time intervals for a 10-year period using GCM grid points in and surrounding the 1.6 million km² Mackenzie River Basin in north-western Canada. The water surpluses from each grid point were accumulated to provide a simulated hydrograph at the outlet of the Mackenzie Basin. The hydrological model was calibrated and verified using five years of recorded climatological and hydrometric data as well as land cover data from NOAA AVHRR images. The climatological outputs from the GCM were then used as inputs to the hydrological model, generating a further hydrograph for the Mackenzie River. It was found that, by itself, the GCM overestimates water excesses or runoff within the basin and that using a hydrological model with the GCM climatology produces a better representation of the recorded flow regime. The method allows verification of a GCM performance.
Keywords: Climate change, GCM, Hdrolological modelling, Mackenzie River Basin

Snow estimation and updating system (SEUS) - McMannamon, A.; Hartman, R.K.; Hills, R. (62nd Annual Western Snow Conference, 1994)
The National Weather Service office of Hydrology has developed a methodology to generate real-time, gridded snow water equivalent estimates using ground-based and airborne snow data collected over the Western U.S. The gridded snow water equivalent estimates incorporate the spatial variability of the snowpack induced by the orographic effect in the west. The Snow Estimation and Updating System (SEUS) uses the power of a geographic information system to store, analyze and display the spatial data necessary to perform the estimation. The point snow water equivalent are interpolated into a gridded product using data derived during the calibration step. The average snow water equivalent estimates over subareas within each basin are used to update the snow water equivalent states of National Weather Service River Forecast System conceptual snow model.The system was used during the 1993 snow season to estimate snow water equivalent over the Colorado Basin above Lake Powell and to update several forecast basins. For the 1994 snow season, snow water equivalent was also estimated for portions of the Lower Colorado Basin and several basins in the Salt and Verde drainages have been added for updating. The system is comprised of a calibration component which developes the parameters specific to a basin, and an operational component which performs the interpolation in real time and estimates snow water equivalant.
Keywords: GIS, Grid model

Mean annual precipitation and variability in Idaho - Molnau, M.; Newton, C. (62nd Annual Western Snow Conference, 1994)
The mean annual precipitation and its variation in time and space are required for many design procedures. A map showing the isohyetal lines of mean annual precipitation for 1961-90 in Idaho was prepared using data from a wide range of sources. A total of 278 precipitation stations with measured data were used together with estimates made at 130 snow courses. Estimates were made for many areas using local expertise and local elevation-precipitation-aspect relationships.The monthly precipitation was derived using regionalized curves of percent of annual precipitation that falls in any month. The monthly precipitation is found by using the mean annual precipitation and multiplying by the appropriate regional curve.The percent of the mean annual precipitation that falls in the winter six months can also be regionalized. On average, approximately 60 percent of the annual precipitation falls during October-March. This ranges from a low of 54 percent in the Bear River basin to 66 percent in the Middle Snake and Panhandle basins.The corfficient of variation of the mean annual precipitation ranges from 15 to 30 percent. This plots as a relatively smooth contour with the highest value in the Bear River basin (30 percent) and the lowest in the Clearwater and Panhandle basins (18 percent).
Keywords: Estimating precipitation, Isohyetal maps, Isohytes, Precipitation, Variability

Snowfall and snowmelt estimates for modern and last glacial conditions within the Owens Valley, California - Orndorff, R.; Craig, R.G. (62nd Annual Western Snow Conference, 1994)
We estimate monthly snowfall, snowmelt, and resulting snowpack for a two-dimensional solution domain which includes California's Owens Valley. A statically-based local climate model computes monthly temperature and precipitation for a 160 by 290 km domain at a 2 km grid cell spacing for last glacial maximum (LGM) and present boundary conditions. The fraction of monthly precipitation that falls as snow is computed as the double integral of a bivariate normal distribution in temperature and log precipitation. We use the methodology of Martinec et al (1983) to compute monthly snowmelt. The snow model computes monthly snowfall, snowmelt, and resulting snowpack at each grid cell, and it estimates the densification of perennial snowpack and its transformation into gracial ice when appropriate. The model proceeds year-by-year until monthly snow and ice total equilibrate.
Keywords: Estimates, Glaciation, Snowfall, Snowmelt

Snow depth measurement using ultrasonic sensors and temperature correction - Osterhuber, R.J.; Edens, T.; McGurk, B.J. (62nd Annual Western Snow Conference, 1994)
Snow depth is commonly measured by visual observation, thus limiting the availability and frequency of observations in remote areas. Ultrasonic depth sensors can overcome this limitation by allowing automated snow depth measurement at remote, unstaffed sites. An ultrasonic sensor determines the distance between a surface and itself by measuring the transmission time of a sound pulse reflected off the surface. The sensors are used in industry and water resources management for a variety of purposes. Measurement errors arise both from temperature-based changes in the speed of sound and from the effect of temperature on the electronics of the sensor. These problems may be reasons that the instrujments have not seen widespread use in snow hydrology. We installed two sensors, one with on-board temperature compensation and one without, to follow changes in snowpack depth during the winter of 1993in California's Sierra Nevada. Sensor depths agreed well with daily visual observationjs, but depth flucuations, measured quarter-hourly, were evident with both sensors and correlated to changing air temperature. Air temperature waw measured independently at the site, and two algorithms were designed that used air temperature or air and instrument temperature to remove the spurious depth flucuations.
Keywords: Snow depth, Sonic sensors

Snowmelt water supply research in the ARS global change, water resources, and agriculture program - Rango, A.; Cooley, K.R. (62nd Annual Western Snow Conference, 1994)
The impending global warming expected to be felt most significantly in the next century will likely have a major impact on water resources and, in particular, snowmelt water supply. The Agricultural Research Service has a Global Change, Water Resources, and Agricultural Research Program in place with the purpose of evaluating the hydrologic impacts of these changes, mostly through the use of snowmelt runoff models. Seven basins in the Western U.S. are being studied. During the snowmelt season, global warming will cause a shift forward in the timing of runoff along with greater amounts of runoff early in the snowmelt season with decreases in runoff during the dry season. In addition there is a shift of runoff from the summer half year to winter half year. Improvements in model representations of evapotranspiration, the radiation balance, and sub-basin areas gives a more physical basis to estimates of the hydrologic response to conditions of climate change. The development and use of integrated modular modeling systems has been necessary to make optimum use of high technology capabilities.
Keywords: Climate change, Modelling, Snowmelt runoff

Potential effect on water project yield of changed snowmelt runoff patterns - Roos, M. (62nd Annual Western Snow Conference, 1994)
One of the potential changes of global warming would be a shift in runoff patterns in temperate zone mountains with less spring snowmelt and more direct winter rain runoff. The Mokelumne River, located in the central Sierra Nevada range of California, was examined to see how this shift in runoff pattern would affect water supply yield. The shift reduced April through July runoff by an average of 28 percent with a corresponding increase in winter runoff, some of which had to be released for flood control purposes. However, the loss in water project dependable urban supply was only 1 to 3 percent. Part of the reason for the small change was the fact that total reservoir storage capacity exceeds average annual runoff of the basin. Another factor was the relatively uniform monthly demand, which generates a smaller dry season draft than an equivalent annual agricultural demand. The level of demand also has an influence; water systems operating beyond their firm yield limit will be more stressed by changing runoff.
Keywords: Agricultural demand, Runoff patterns, Snowmelt

Assessing the importance of snowmelt water supply from 'historical' records of snow accumulation and runoff, Jhelum catchment, Pakistan Himalaya - de Scally, F.A. (62nd Annual Western Snow Conference, 1994)
The importance of snowmelt water supply in the Jhelum River catchment is assessed by comparing the ‘historical’ records of winter snow accumulation and runoff in Pakistani sub-basins. The snow accumulation records, although only five to eight years long, represent the only such data available for this region of the western Himalaya. Strong statistical correlations are found to exist between point measurements of the annual maximum of snowpack water equivalent or total winter precipitation, and total annual runoff. Point measurements of total winter snowfall also show a generally significant correlation with annual runoff. Other evidence reinforces the conclusion that snowmelt is the dominant source of annual runoff, and indicates the potential value of such snow accumulation measurements for predicting seasonal and annual runoff, particularly since remotely sensed data have so far been difficult to obtain. However, such predictions may be complicated in this region by the effects of a continental-scale feedback mechanism between snow cover and the summer monsoon.
Keywords: Jhelum River, Pakistan, Snow courses

Instantaneous measurements of snowdrifts in small-scale modeling - Schmidt, R.A.; Jairell, R.L. (62nd Annual Western Snow Conference, 1994)
Side-by-side comparisons of small-scale models in drifting snow can quickly answer questions about efficient drift control. However, measuring snowdrifts simultaneously as they accumulate near paired models requires a faster method than probing each drift with a ruler. We explored computer imaging for a possible alternative. Analyzing photographs of a 'rake' of vertical pinjs pressed in to the drift produced promising results. Usint the method, we compared trapping efficiency of model tree rows with model snow fences, as an example.
Keywords: Computer imaging, Models, Small scale models, Snowdrifts

Snowdrifts and the aerodynamic drag on scaled-model shelterbelts - Schmidt, R.A.; Jairell, R.L.; Tabler, R.D. (62nd Annual Western Snow Conference, 1994)
This paper reports the design and initial testing of a device that measures the wind force model windbreaks. Our objective is to improve understanding of the relationship between shelterbelt porosity, aerodynamic drag, and snowdrift formation. Two identical drag-boards allow simultaneous comparison of drag on a model shelterbelt with drag of a snow fence model for which the prototype drag coefficient is known.
Keywords: Aerodynamics, Scale models, Snow drifting

Snow accumulation and ablation under fire-altered lodgepole pine forest canopies - Skidmore, P.; Hansen, K.; Quimby, W. (62nd Annual Western Snow Conference, 1994)
Clearcut, burned, and undisturbed lodgepole pine forests in southwestern Montana were studied to determine if forest fire increased snow accumulation and ablation rates on the forest floor. Snow depth, snow density, and snow water equivalence data were collected at each plot throughout the ablation period during the 1992 snow season and the accumulation and ablation periods during the 1993 snow season. Forest variables including percent canopy cover, basal area, and tree height were measured during the 1992 summer season to assess the effects of forest cover on snow variables. The burned forest canopy produced a 9 percent increase in snow water equivalence accumulation as compared to that produced by the mature forest stand. Canopy reduction in the burned forest stand resulted in an ablation rate up to 57 percent greater than that in the mature forest stand. The forest structures of the burn and of the clearcut produced similar snow accumulation and ablation responses.
Keywords: Basal area, Lodgepole pine, Snow accumulation, Snowmelt, Stand density

Boreal forest snowpack research for global change - Slaughter, C.W.; Viereck, L.A. (62nd Annual Western Snow Conference, 1994)
Discontinuous-permafrost landscapes are highly vulnerable to potential global change. The seasonal snowpack in northern boreal forest settings will respond to and will influence global warming, predicted to be earliest and of greatest magnitude at high latitudes. Research toward assessing global change is being conducted at a Taiga Long-Term Ecological research facility in central Alaska. Baselines of snow accumulation, ablation and chemistry are being developed, building on more than two decades of ecosystem research and monitoring. Complimentary research is conducted on ecological and hydrological processes in forest stands from lowland floodplain through upland slopes (both cold, permafrost-underlain and warm, permafrost-free) to treeline.
Keywords: Climate change, Ecological research, Global change

Using the WRNSHYD procedure to estimate long-term cummulative effects of aspen clearcutting on water yield in Alberta - Swanson, R.H. (62nd Annual Western Snow Conference, 1994)
Snow accumulation, evaporative loss of snow, summer evapotranspiration and ultimately water yield are affected by clearcut harvesting. As harvesting progresses through time, regrowth occurs that limits the effect that wind can have on the transport and redeposition of snow from clearcut areas. Basal area also increases, altering the effect on evapotranspiration. Regrowth can be estimated and input into the hydrology portion of the USFS Water Resources Evaluation of Non-point Silvicultural Sources (WRENSS) procedure to obtain an estimate of the cumulative effects of harvest through time.The hydrology section of the WRENSS procedure indicates that if the height of regrowth is greater than the depth of the snowpack, wind driven snow transport and loss in transport are nil. This generally occurs by the second year after clearcutting in the boreal forest of Canada where aspen regrowth occurs rapidly from root sprouts after clearcutting. Basal area increases to about 30 sq m/ha in the first 30 years after harvest and by year 20 is sufficiently high so that the estimated increases in evapotranspiration are essentially nil. The net effect in WRENSS of the combined effects of clearcutting on snow accumulation, snow transport, loss in transport and evapotranspiration is zero for any single clearcut in aspen forest of the region by 25 years after harvest.The cumulative effects of periodic harvests within a 546 km² watershed over various time intervals were estimated to determine possible harvesting regimes in order to maintain the annual water yield increase below 15% at the first significant user, a criterion established by Alberta Environment to minimize flooding impacts on downstream residents and water users. Three harvesting scenarios were simulated: 1) continuous harvest of 400,000 cu m/yr until all of the merchantable timber is removed (approximately 15 years), 2) continuous harvest at 200,000 cu m/yr for 30 years and 3) continuous harvest at 100,000 cu m/yr over a 60 year rotation. The first scenario is the only one that resulted in a maximum increase (21%) in water yield greater than 15% at the boundary of the watershed. The other two scenarios resulted in maximum water yield increases of 11% and 6% respectively.
Keywords: Clearcutting, Cumulative effects, Evapotranspiration, Model, Simulation, Snow transport, WRENSS

Comparison of satellite snow cover estimates from NOAA snow charts and a SMMR show cover algorithm - Tait, A. (62nd Annual Western Snow Conference, 1994)
This study compares two satellite-derived snow cover estimates with ground-based monthly snow cover measurements from the former Soviet Union. The satellite data are from NOAA/NESDIS snow charts, computed from reflected visible radiation, and an algorithm developed by Chang et al. (1987) which determines snow cover as a function of two Scanning Multichannel Microwave Radiometer (SMMR) microwave frequencies (18 and 37 Ghz).Results show the data agree relatively well during winter and summer months, but less well in spring and fall. It is argued that the SMMR algorithm underestimates snow cover conditions during spring and overestimates in fall as brightness temperatures are strongly affected by the presence of liquid water and frozen ground respectively. In addition, the visible data composites show disparities caused by extensive cloud cover, a rapidly moving snow boundary, and the use of monthly summary snow charts.
Keywords: Microwave, Satellites, SMMR, Snowcover

Tioga Pass revisited: Interrelationships between snow algae and bacteria - Thomas, W.H. (62nd Annual Western Snow Conference, 1994)
Previously (1969-70) snow algae were studied at Tioga Pass, Sierra Nevada, California. Red snow algae were identified; their distribution was patchy; and they were actively photosynthetic. In July-August 1993, red snow patches were abundant in this same area and biological comparisons were made between red and non-colored snow. Algal cells were often about 750 times more abundant in red snow than in white snow; and no chlorophyll was detected in white snow while red patches contained up to 0.1 µgm chlorophyll mL /snow. Bacterial abundance in white patches were only one-third to one-eight those in red snow and dissolved organic carbon was also lower. In red snow the incorporation rates of ³H-leucine into bacterial protein were 103-295 times less than algal photosynthesis rates when both were expressed as µgm C taken up mL/snow/h. Bacterial production rates were also lower in white snow than in red snow. These results suggest that bacteria were intimately associated with algae in the snow and that bacteria may have been utilizing carbon excreted by the algae. This hypothesis needs to be confirmed by labeling algae with radioactive carbon, isolating the C-14 excreted by the algae, and feeding it back to bacteria in snow patches.
Keywords: Algae, Organic carbon, Red snow

Spatial snowfall distributions in winter storms in Colorado - Tollerud, E.I.; Mahoney, J.L.; Collander, R.S. (62nd Annual Western Snow Conference, 1994)
Snowfall data from storms in Denver and Colorado Springs, Colorado, are used to confirm the finding from previous studies that snowstorms in Denver are characteristically distinct from snowstorms in Colorado Springs. From analyses of storms in these two cities during the period 1972 to 1992, storm-total snowfall at the sites is found to be inversely related; that is, heavy snowfall at Denver is usually associated with relatively light snowfall at Colorado Springs, and vice versa. Hourly liquid precipitation data from a set of several stations in Colorado are totaled over the lifetime of 17 major storms in Denver and 11 in Colorado Springs. Plots of these totals demonstrate that precipitation during major Denver storms is concentrated on the eastern plains of Colorado, while precipitation during major Colorado Springs storms shows large amounts west of the continental Divide. These spatial distributions are compared to composite maps of storm circulation produced by Mahoney et al (1994), which exhibit strong low-level cyclogenesis in the lee of the Rocky Mountains in the Denver storms and low-level cyclogenesis west of the mountains in the Colorado Springs storms.
Keywords: Colorado Springs, Denver, Snowfall patterns

1993 Title, Contents, and Minutes (61st Annual Western Snow Conference, 1993)

Snow and ice in the publications of the Canadian Institute, 1852-1914 - Adams, P. (61st Annual Western Snow Conference, 1993)
This paper, written on the occasion of the 50th anniversary of the Eastern Snow Conference, is intended to re-introduce a valuable repository of published work on snow and ice, the journals of the Canadian Institute. The Canadian Institute (since 1914 the Royal Canadian Institute) was a major outlet for a wide spectrum of pure and applied science, economics, literature and the arts in the latter half of the 19th century and the early years of this. Its journals were important vehicles for the work of Canadian and other scholars, notably physical scientists and engineers, for many decades. The Institute’s publications include The Canadian Journal, a Repertory of Industry, Science and Art, The Canadian Journal of Science, Literature and History, The Proceedings of the Canadian Institute, Proceedings of the Canadian Institute, (New Series). The current address of the Royal Canadian Institute, a good source for sets of these journals, is 720 Spadina Avenue, Suite 312, Toronto, Ontario, M5S 2T9.
Keywords: History, Ice, Publications, Snow

Snowpack stratigraphy evolution at forested and open sites - Albert, M.R.; Hardy, J.P. (61st Annual Western Snow Conference, 1993)
Field observations of seasonal snowpack stratigraphy evolution over the course of a winter are described at open and deciduous forest sites. The predominant stratigraphic features of the two sites were similar, although the snow sometimes had dramatically different behavior in response to tree- and slope-induced local meteorological differences. Differences in solar radiation between the two sites produced differences in early snowcover, which then controlled the formation and nature of the basal ice layer that remained throughout the season. At this location, the greater longwave radiation induced by the trees at the forested, south-facing hill slope offset the greater solar radiation at the open site, so that the net allwave radiation at the two sites was approximately equal. More snowpack mass was lost during snowmelt at the forested hill slope than at the open site because the melt generated in the upper half of the pack flowed laterally through the pack in the down slope direction. At the open site, snowmelt at the surface flowed vertically through the pack, sometimes adding mass to lower layers. In addition, field observations illustrate that capillary effects produce observable changes in snowpack layering, and need to be included in modeling of metamorphic snowmelt processes.
Keywords: Forested site, Open site, Snowpack, Stratigraphy

An approach to assessing changes in snow cover: an example from the former Soviet Union - Barry, R.G.; Armstrong, R.L.; Krenke, A.N. (61st Annual Western Snow Conference, 1993)
The question of what are the most suitable indices of temporal change in snow cover conditions, and the most appropriate means for their detection is important in monitoring climate system changes. The extent and variability of seasonal snow cover is recognized to be an important climatic and hydrologic parameter. Trends in snow cover are also expected to serve as an indicator of any global climatic changes.Passive microwave data afford the possibility of all-weather mapping of daily snow extent, and potentially water equivalent, with a spatial resolution of 25-50 km is well suited for regional and global climate modeling. Newly-released snow depth data for stations in the former Soviet Union are described and for a ten-day average are compared with passive microwave-derived estimates. Possible sources of differences are discussed including problems related to wet snow, mountainous terrain and vegetation, as well as errors caused by the interpolation of station data used for validation.
Keywords: Climate change, Microwaves, Satellite photographs, Snowcover

Mesoscale atmosphere icing event, March 1991 - Bates, R.E.; Fiori, J.E.; Fisk, D.J.; Harrington, B.G. (61st Annual Western Snow Conference, 1993)
During a field experiment designed to characterize winter atmospheric meteorological conditions and the physical properties of the snow cover backgrounds at Fort Drum, New York, a severe atmospheric icing/glaze event occurred. This icing event was documented with an automatic meteorological recording station located near the center of the storm track. The measurement recording was set at a frequency of 10 minutes, and three days of icing precipitation and glaze formation data were measured. Over the three days, varying intensities and/or combinations of freezing rain and drizzle, rain, snow, ice pellets and fog occurred at the measurement site. The severity of this event was described by newspaper headlines such as ‘Ice Storm Closes Jefferson County,’ ‘Ice Creates Emergency’ and ‘Seven Counties in Western and Northern New York State Paralyzed by Ice Storm.’ The synoptic situation during this event included a low pressure center, with supporting cold and warm fronts that combined as an occluded front over central New York state. This front stalled and the resulting mixture of cold and warm air masses included nearly all types of high intensity frozen precipitation. This moisture (when precipitating out of a cloud formation) resulted in up to 1 in (2.5 cm) of ice accretion and glaze formation on all exposed objects over a large geographical area.
Keywords: Glaze, Icing, Rime

Distribution and abundance of microbial biomass in Rocky Mountain spring snowpacks - Brooks, P.D.; Schmidt, S.K.; Sommerfeld, R.; Musselman, R. (61st Annual Western Snow Conference, 1993)
Snowpacks in both Colorado and Wyoming were sampled on 15 dates for total microbial biomass, ratio of bacteria to fungi, and major inorganic ions. Levels of viable microbial biomass remained low throughout the period, peaking at 0.05 micrograms carbon/ml. Microscopic analyses indicated this biomass was composed primarily of bacteria. Fungi were not detected in samples taken at or above tree line. With the exception of one date in early May at the Colorado site, bacteria were confined to a band within the snowpack approximately 20 cm above the snow/soil interface. Laboratory incubations using two Gram negative motile rods isolated from this layer indicated these organisms were capable of growth at 0degC ± 0.5degC but had optimum growth temperatures between 20degC and 37degC. Based on observed population sizes and growth rates it is unlikely these organisms were capable of significantly affecting trace gas emissions or altering the chemical composition of snowmelt.
Keywords: Bacteria, Fungi, Microbes, Micro-organisms

Recent observed trends and modeled interannual variability in Canadian snow cover - Brown, R.E.; Goodison, B.E. (61st Annual Western Snow Conference, 1993)
Analysis of Canadian daily snow depth data revealed a consistent reduction in the duration of snow cover over the period of record (1955-89). This was most marked in southern regions of the Prairies and western Canada where the annual duration of snow cover has decreased an average of 1.0 to 1.5 days/yr over the 35 year period. Most of this decrease occurred in the spring in association with significantly warmer spring temperatures. Analysis of reconstructed snow cover duration data from 1900 in three regions (W. Prairies, S. Ontario and Maritimes) revealed quite different responses and scales of variability. However, a characteristic feature of the data was a trend toward increasing snow cover duration from the late-1920s to the late-1960s, followed by a rapid decrease during the 1970s and 1980s. The lack of a consistent relationship between snow cover and air temperature highlighted the complex nature of snow-climate interactions in Canada.
Keywords: Snow cover

Groundwater temperatures during the winter in a forested basin - Calkins, D.J. (61st Annual Western Snow Conference, 1993)
Vertical groundwater temperature profiles were measured in shallow (1-4 m) 5.08 cm diameter PVC wells at several sites within a small (0.47 km²), deciduous forested basin. All sites except one indicated that conduction was the predominant means of heat transport, as was evident by the profiles being close to linear with depth. At one site the temperature was uniform with depth, indicating that the advecting fluid kept the temperature profile shape from changing significantly during the entire fall or winter season.By the end of winter and just prior to snowmelt, groundwater temperatures at the 2 m depth ranged between 2 and 4.25degC, and were warmest at highest elevations in the basin. The spatial variability in groundwater temperatures at the 2 m depth at all sites was nearly 2degC throughout the winter period.The presence of a snow cover minimizes the infiltration of rainwater and subsequent advection of heat to the soil. A preliminary analysis of the data has shown that late in winter, the assumption of a steady state heat flux can be made. Vertical upward velocities in saturated soil regions on the order of 0.05 m/day were computed from a one-dimensional steady state heat and mass flow analysis using the temperature profiles.
Keywords: Groundwater, Snowcover, Soil Temperature, Temperature

Increasing the precision of snow water equivalent estimates obtained from spatial modeling of airborne and ground-based snow data - Carroll, S.S.; Carroll, T.R. (61st Annual Western Snow Conference, 1993)
With the increased demand for water in the United States, Particularly in the West, it is essential that water resources be accurately monitored. Consequently, the National Weather Service maintains a set of conceptual, continuous, hydrologic simulation models used to generate extended streamflow predictions, water supply outlooks, and flood forecasts. A vital component of the hydrologic simulation models is a snow accumulation and ablation model that uses observed temperature and precipitation data to simulate snow cover conditions. The simulated model states are updated throughout the snow season using snow water equivalent estimates obtained from airborne and ground-based snow water equivalent data. The National Weather Service has developed a spatial geostatistical model to estimate snow water equivalent for updating the snow model. In this research, we describe how to increase the precision of the snow water equivalent estimates by incorporating knowledge of the measurement errors that exist in the airborne and ground-based data in to the spatial model.
Keywords: Conceptual models, Models, Remote sensing, Snow cover

Measuring alpine snow depths by digital photogrammetry. Part 1. Conjugate point identification - Cline, D.W. (61st Annual Western Snow Conference, 1993)
In this study, we examine the use of softcopy (digital) photogrammetry as a method of measuring the spatial distribution of snow depths, with the assumption that snow depth contributes most of the spatial variance associated with snow water equivalence in alpine basins. The primary obstacle with which we were confronted was the ability to determine the parallax of conjugate points in an aerial stereopair using automated pattern matching techniques. Snow is often considered to be one of the most difficult surfaces for pattern matching algorithms. We have found, however, that sufficient snow surface texture exists in our alpine study area on Niwot ridge to enable successful automated pattern matching in many locations. This sets the stage for using softcopy photogrammetry to measure spatial distribution of snow depth in alpine basins, thus is an important step forward in our use of distributed-parameter hydrologic models in snowmelt-dominated alpine basins.
Keywords: Aerial photography, Alpine, Snow depths

Aerosol scavenging by falling snow - Cragin, J.H.; Hewitt, A.D. (61st Annual Western Snow Conference, 1993)
Removal of atmospheric aerosols by falling snow flakes was studied during several winters in Hanover, New Hampshire, using micrometer-sized particles. Experiments were performed in open air and within static and dynamic aerosol chambers. The primary scavenging mechanism for particles in this size range was inertial impaction. Scavenging efficiencies were determined by collecting and chemically analyzing snow flakes that were allowed to fall naturally through the static chamber containing a cloud of known aerosol concentration. The averaging scavenging efficiency (defined as the ratio of the mass of aerosol collected by the snow flake to the total mass of aerosol in the swept volume) of several different types of snow flakes and ice crystals was 0.11 ± 0.08. Higher scavenging efficiencies were observed for three-dimensional spatial dendrites than for planar crystals, such as planar dendrites and hexagonal plates. Overall, snow was found to be four to five times more efficient that rain in scavenging 0.3-to 6µm-sized particles. Laser attenuation measurements within a dynamic aerosol chamber indicated that particle scavenging can cause relative transmission increases of as much as 15% for each minute of exposure to snowfall. Model calculations predicted aerosol cloud half-lives of 2 to 20 minutes for snow precipitation rates of 2.5 to 0.5 cm/hr.
Keywords: Crystals, Scavenging, Snowflakes

Estimating total snow volume in a small alpine watershed using remotely sensed data and ground-based surveys - Davis, R.E.; Elder, K.; Rosenthal, W.; Melack, J.; Sickman, J. (61st Annual Western Snow Conference, 1993)
Ground surveys of snow water equivalence and snow cover maps derived from Landsat TM imagery provided the basis for investigating different methods to estimate total snow volume in a small watershed of the eastern Sierra Nevada of California. Snow density profiles and Federal Snow Sampler observations along ground transects made up the measurements used to estimate the snow water equivalence at several points. The area of snow cover was estimated with two techniques, a supervised classification and a method based on spectral mixture modeling. Total snow volume was obtained by distributing snow water equivalence over the snow-covered area with the help of a digital elevation model. Snow volume estimates, in terms of their water equivalence, were compared with the estimated total snowmelt runoff. Total snowmelt runoff was estimated by subtracting baseflow determined with a graphical technique. The comparisons were evaluated in the context of potentially combining remote sensing data with traditional snow course measurements to determine total snow cover volume.
Keywords: Remote sensing, Snow cover

Can avalanche activity alter the pattern of snowmelt runoff from high-mountain basins? - deScally, F.A. (61st Annual Western Snow Conference, 1993)
Avalanche activity can affect the subsequent generation of snowmelt runoff as a result ot two main changes occurring during avalanching: concentration of the snow mass, and an ambient temperature increase resulting from the avalanche’s fall to a lower elevation. The balance between these changes largely determines whether the rate of meltwater production from individual avalanche deposits is decreased or increased in comparison to undisturbed snow. Any noticeable effect on the temporal pattern of snowmelt runoff at the basin scale depends first on the proportion of the total basin snow cover which has been disturbed by avalanching, and second on the balance between delayed and accelerated meltwater production from all avalanche deposits in the basin in the basin. This paper discusses the effect of avalanche activity on runoff from a large (2500 sq km) basin in the Punjab Himalaya, Pakistan and ongoing research from small high-elevation basins in the Cascade Mountains, British Columbia.
Keywords: Avalanche, Snowmelt, Watersupply

Composition physico-chimique de la neige artificelle et les impacts des eaux de fonte sur deux espèces végétales des écosystèmes montagneux au Québec - Devarennes, G. (61st Annual Western Snow Conference, 1993)
L’utilisation de plus en plus de neige artificelle sur des pentes de ski pour allonger la saison de ski pourrait avoir un effet sur l’hydrogéochimie des eaus de ruissullements, la composition physico-chimique du sol ainsi que la régénération de certains types de végétation. Afin d’évaluer les répercussions de l’épandage de la neige artificielle sur des écosystèmes montagneux, nous avons caractérisé la composition chimique de la neige artificielle d’après l’eau utilisée pour sa fabrication au Mont-Sainte-Anne, Québec, Canada. Nous avons de plus comparé la composition chimique des eaux de fonte provenant de la neige naturelle et de la neige artificielle ainsi que de leur impact sur les taux de germination de deux espèces montagneuses: le bouleau jaune (Betula lutea) et l’épinette blanche (Picea glauca). Les résultats des éstudes sur la fonte des neiges en laboratoire ont démontré qu’en dépit de leurs origines différentes et des grands écarts entre leurs compositions chimiques relatives, la distribution des ions majeurs dans les gouttelettes congelés fabriquées par des canons à neige est semblable à celle de la neige naturelle ayant des cristaux de formes arrondie. On peut ainsi simuler la composition de la fonte de neige par des modèles déjà utilisés par la neige naturelle. Les résultats des études sur la germination du bouleau jaune et de l’épinette blanch ont permis de conclure que même si les concentrations des espèces chimiques dan les eaux de fonte de neige artificielle étaient de 2 à 40 fois supérieures à celles dans la neige naturelle il ne semble pas y avoir d’effet sur la germination de ces deux espéces.
Keywords: Artificial snow, Chemical properties, Germination