Estimating localized SWE on the Yellowstone northern range - Farnes, P.E.; Romme, W.H. (61st Annual Western Snow Conference, 1993)
After the large fires of 1988 in Yellowstone National Park, many projects were initiated to study their effects. One of the studies involved the effects of fire on vegetation and ungulates on the northern winter range.Because snow water equivalent (SWE) is a significant factor in animal foraging and movement, it was necessary to develop a method that could use data from National Weather Service (NWS) climatological stations and Soil Conservation Service (SCS) snow courses and SNOTEL (SNOw Survey TELemetry) sites to predict SWE in areas of varying slopes, aspect, elevation, and forest cover. It was first necessary to estimate SWE at NWS climatic stations. The daily snow depth, precipitation and temperature values were used to estimate daily SWE. Daily SNOTEL SWE was used to estimate daily SWE at SCS snow courses. Algorithms were developed to estimate daily SWE for flat and open areas on the northern range not having significant drifting similar to data collection sites.A multidimensional nomograph was developed from measured data to estimate SWE for any slope and aspect within the northern range area. The habitat cover type was used to adjust SWE for forested areas.Techniques and relationships developed for the northern range would be transferable to other intermountain areas that accumulate a winter snowpack and that have daily climatic and/or snow pillow data.
Keywords: Algorithm, SNOTEL, Snow cover

North American snow cover variability from satellite data (1972-1993) and comparison with model output - Frei, A.; Robinson, D.A. (61st Annual Western Snow Conference, 1993)
A twenty-one year record of remotely-sensed areal snow cover fluctuations for the Northern Hemisphere is examined, with particular emphasis placed on North America. No trend is apparent, but several periods of positive and negative departures are found. The mid- to late-1970s, and the mid 1980s, had large snow covered areas. The early 1980s, and the period since 1987, are characterized by low snow cover. The most temporally extensive of these has been a period of snow deficit since 1987, particularly in spring and in eastern North America. The five lowest North American spring snow covers on record have occurred since 1987. In autumn, three of the last five years have been extremely low. Recent winters have not been anomalous. Results from one climate model are compared to observations, and are found to simulate accurately winter snow cover on the continental scale, while slightly under-estimating spring and autumn values. On the regional scale, the model is less accurate. Snow cover may be critical for model validation, improvement of parameterizations, and for prediction and detection of climate change.
Keywords: Climate change, Model, Snow cover

River ice conditions determined from ERS-1 SAR - Gatto, L.W. (61st Annual Western Snow Conference, 1993)
CRREL has received digital data for 15 European Space Agency (WSA) European Remote Sensing (ERS) Satellite-1 synthetic aperture radar (SAR) images of the St. Marys, Connecticut and White Rivers, acquired from 16 December 1992 to 5 May 1993. Satellite-borne SARs such as those onboard ERS-1 acquire radar image data in all weather conditions and at night. Data for four of the 15 images have been processed to determine ice conditions on the rivers as detected by this satellite-borne SAR. Extensive data bases of past ice conditions on the rivers, ground observations, ice thickness measurements and low-altitude aerial photographs collected during or within three days of ERS-1 overpasses were used to evaluate SAR image patterns resulting from the river ice on the four images. The preliminary results of the evaluations suggest that satellite-borne SARs will provide data on river ice conditions that are necessary for navigating through ice and evaluating the potential for river ice jams and ice erosion along shorelines.
Keywords: Ice conditions, Satellite

Disaggregation models of seasonal streamflow forecasts - Grygier, J.; Stedinger, J.R.; Hongbing, Yin; Freeman, G.J. (61st Annual Western Snow Conference, 1993)
Pacific Gas and Electric Company (PG&E) has developed a regression-based procedure for disaggregating a seasonal runoff forecast into monthly flow forecasts. These forecasts can be used to estimate the most likely or mean value for each month’s runoff, or to estimate runoff for particular meteorological scenarios, given current conditions. Four basic seasonal-to-monthly disaggregation model families were studied: (1) linear, (2) polynomial, (3) exponential, and (4) logit. The logit model, which ensures that monthly forecasts are always non-zero and less than the forecasted seasonal volume, had larger or comparable R² than the polynomial and exponential models, so the later two were dropped from further analysis. A program was developed which considers the linear and logit models with up to three explanatory variables: the total seasonal forecast, previous month’s flow, and future monthly precipitation. It can select, using standard statistical criteria, a model reasonable for each site and season.
Keywords: Forecasts, Model, Statistical methods

Snowdrift modeling in the CRREL wind tunnel - Haehnel, R.B.; Wilkinson, J.H.; Lever, J.H. (61st Annual Western Snow Conference, 1993)
We modified CRREL’s snow drifting wind tunnel to generate a flow field that simulates the atmospheric boundary layer and installed a trap for measuring the average mass flux. We replaced the previously used activated clay with glass beads and developed a moiré photography system to measure drift profile.We then conducted a series of preliminary calibration tests to verify the similarity of model and full-scale snowdrifts. Two-dimensional calibrations included a Wyoming snow fence and a step. Three-dimensional tests included a right circular cylinder and a rectangular prism. Generally, the agreement was good between model and prototype drift geometry’s. However, there is insufficient quantitative field data available to thoroughly validate the model results.
Keywords: Scale models, Snow drifting, Wind tunnel

Analysis of visible and microwave satellite data for snow mapping in Alaska - Hall, D.K.; Benson, C.S.; Chien, J.Y.L. (61st Annual Western Snow Conference, 1993)
Analysis of passive microwave Defense Meteorological Satellite Program (DMSP) Special Sensor Microwave Imager (SSMI) data, in conjunction with Advanced Very High Resolution Radiometer (AVHRR), topographic data and vegetation maps has been undertaken for a period of time in 1989 in Alaska. The combined use of visible, near-infrared and microwave sensors to map snow will lead to an improved ability to map snow extent, albedo and water equivalent. Such data are available now from the AVHRR, and in the future, from the Earth Observing System Moderate Resolution Imaging Spectroradiometer (MODIS). Passive microwave sensors are necessary in order to augment visible and near-infrared sensors which cannot acquire data through cloud cover and darkness. Results show a strong dependence of the microwave brightness temperature on topography, and land cover. Also, the influence of persistent meteorological conditions on snow temperature is hypothesized as an explanation for a brightness-temperature anomaly observed during the winter in the northern foothills of the Brooks Range, Alaska.
Keywords: Microwaves, Passive microwaves, Radiometers, Satellite, Snow cover

The permeability of temperate snow: Preliminary links to microstructure - Hardy, J.P.; Albert, D.G. (61st Annual Western Snow Conference, 1993)
The intrinsic permeability of snow is an important parameter controlling meltwater flux through a snowpack and snowpack ventilation. Few measurements have been made on the permeability of seasonal snow covers, particularly in temperate zones where ice layers have an important control on the permeability. The purpose of this research was to correlate field measurements of permeability with physical properties of snow.Throughout the 1992-93 winter season, field measurements were made, using an air permeameter, to determine the permeability of different snow types in northern Vermont. Concurrent with the permeability measurements, the physical properties of each stratigraphic layer were measured and samples for microstructural analysis were collected.Permeability values ranged from 3 to 75 x 10-10 sq m and agreed with previously published data. No correlation was found between field-measured physical properties and snow permeability. Stereologic parameters for dry snow correlated well with permeability, but for old snow, especially ice layers, the correlation was poor.
Keywords: Permeability, Snow structure

Snowmelt-induced slushflows, Ellesmere Island, N.W.T., Canada - Hardy, D.R. (61st Annual Western Snow Conference, 1993)
At Taconite Inlet, northern Ellesmere Island, Canada (82deg 50 min N; 78deg 00 min W), a snowmelt-induced slushflow marked the beginning of streamflow in 1992 from the Lake C2 watershed. Meteorological, snowpack, and hydrological measurements were made during May and June prior to the slushflow, to test a hypothesis that the most likely slushflow initiation site was beneath a large south-facing slope. Four days before the slushflow, the snowpack in flat areas was still sub-freezing (e.g. basal temperatures -9deg to -11deg C), with maximum snow wetness less than 1 percent (by volume). In contrast, the south slope snowpack by this time was warmer and afternoon snow wetness was reaching 2 to 5 percent, due to higher radiative inputs. Following three days of vigorous turbulent heat transfer, a slushflow began in the stream channel below the south slope and traveled 1600 m to the lake. Discharge during the event was the highest observed during three summers (5.5 +/- 2 m³/s), yet was insufficient to breach avalanche debris snow dams. Additional slushflows occurred elsewhere in the watershed during the following week.
Keywords: Slushflows

Examining the influence of snow cover on morning air temperature - Hogan, A.; Ferrick, M. (61st Annual Western Snow Conference, 1993)
There are large differences in mean minimum winter air temperature among very proximate New England stations. Daily differences are even greater when research sites are compared. We conducted a series of experiments, in morning twilight during the winter months, to examine the influence of topography and snow cover on early morning air temperature. We have proposed a hypothesis that the impoundment of the Connecticut River extending above the Wilder dam provides a temperature reference plane, allowing evaluation of physical factors modifying air temperatures adjacent to the reference plane. Analyses of surface air temperature with respect to elevation and distance along the Connecticut River valley show consistent vertical temperature structures that are related to snow cover. We present analyses of temperature structure and the relation of surface air temperature to vertical temperature structure in the vicinity of the reference plane.
Keywords: Local influence, Temperature

Snow algae and other microbes in several alpine areas in New England - Hoham, R.W.; Laursen, A.E.; Clive, S.O.; Duval, B. (61st Annual Western Snow Conference, 1993)
Snow algae and other microorganisms are reported from green and orange snowpacks from New England during spring 1992 and 1993. Sites sampled include Mt. Katahdin and Sunday River Ski Area, Maine; Ashland, Hawley, Mt. Greylock and Wachusett Mtn. Ski Area, Massachusetts; Monadnock Mtn. And Mt. Washington, New Hampshire; Mansfield and Stowe Ski area, Vermont. Dominant snow algae belong to the green algal flagellate Chloromonas. Other microbes include snow fungi bacteria, ciliated protozoa, nematodes, rotifers and tardigrades. Laboratory cultures reveal several species of yellow-green algae and green algae not previously reported from snow in eastern North America. Two species of Chloromonas are newly discovered snow microbes, and one appears to be restricted to ski slopes. The distribution and diversity of snow microbes in eastern North America is greater than previously realized. New England isolates of Chloromonas will be used in laboratory studies to further our understanding of snow algal reproductive strategies and physiological ecology.
Keywords: Microorganisms, Snow algae

Snow cover variability in the Great Plains of the United States: 1910-1988 - Hughes, M.G.; Robinson, D.A. (61st Annual Western Snow Conference, 1993)
The duration of seasonal (September-May) snow cover over the Great Plains of the United States has varied considerably this past century. A statistically significant trend toward a greater duration of snow cover from 1910 to 1988 shows region-wide average of 29 days early in the century increasing to 38 days in recent decades. Variability of snow cover duration from year to year has also increased, exhibiting the largest changes in the northwest, central and southeastern parts of the region. Fluctuations on the order of a decade are imbedded in this upward trend i.e., low snow cover in the 1930s, and high snow cover in the 1970s. Decadal variations are associated with changes in both snowfall and temperature; however, only snowfall has shown a statistically significant increase since 1910. The reliance on snow cover for hydrologic and agricultural purposes in this part of the country, the sensitivity of the boundary layer climate to snow cover conditions in the Plains, and the projections by global climate models for this region to become warmer and dryer as a result of increasing atmospheric concentrations of greenhouse gases, necessitates a better understanding of the variability of snow cover over the Plains.
Keywords: Climate change, Climate variability, Snow cover

Southern Michigan's snow belt -- modelled impacts on soil temperatures and freezing - Isard, S.A.; Schaetzl, R.J. (61st Annual Western Snow Conference, 1993)
A physically-based computer model is developed for estimating soil temperatures at 0.05, 0.1, 0.2, and 0.5 m depths in sandy, forested soils, using daily minimum and maximum air temperatures and precipitation as input data. The algorithm is evaluated by comparing its output to 490 soil temperature observations for 1990-93 at stations in southern Michigan. The mean errors of the soil temperature estimates are less than 0.1deg C at the 0.5 m depth, thus comparing favorably to models requiring more detailed input. The model is applied to 14 stations across lower Michigan, using 1951-91 climatic data, in order to examine regional trends in soil temperature and freezing and to compare these trends to patterns of snow thickness and air temperature. Simulations reveal that soils seldom freeze within the deep snow area (lake-effect snow belt) of southern Michigan and along the coast of Lake Michigan. Soil freezing is more common at non-snowbelt, interior locations.
Keywords: Algorithm, Model, Soil temperatures

The relationship of the annual snowpack to the water yield from the inner basin of the San Francisco Peaks, Arizona - Jones, R.A. (61st Annual Western Snow Conference, 1993)
During the period 1970-1991 the glaciofluvial deposits in the inner basin of the San Francisco Peaks, Arizona, have produced as much as 28% and as little as 2% of the annual water supply of the city of Flagstaff. This water is produced from wells and developed springs. Regression analysis indicates that water production shows a good correlation with maximum snow water equivalent, especially the production of the springs (r = 0.92). However, scheduled snow surveys may miss the maximum snow water equivalent measurement. The installation of a SNOTEL telemetry site would produce a daily record, thus insuring this maximum measurement. The SNOTEL data should contribute to the development of better water production forecasts.
Keywords: Forecast, SNOTEL, Statistical analysis

Snow-atmosphere interactions in Arctic snowpacks -- net fluxes of NO3, SO4 and influence of solar radiation - Jones, H.G.; Pomeroy, J.W.; Marsh, P.; Davies, T.D.; Tranter, M. (61st Annual Western Snow Conference, 1993)
Identical experiments on snow-atmosphere interaction were carried out at two arctic sites (open forest and tundra, Inuvik, Canada) prior to spring snowmelt, April 1992. The purpose of the experiments was to estimate the magnitude and direction of net fluxes (dry deposition/re-emission) of NO3 and SO4 between the snow surface and the atmosphere from changes in concentrations of these species in the surface snow over periods of 36-48 hours. The experiment was also designed to determine the influence of solar radiation on fluxes of NO3 and SO4. The methodology included a procedure to homogenize surface snow; this served to normalize the initial chemical conditions for all sample sets used in the experiment. The homogeneous samples were exposed to the atmosphere in a series of mesh bags which allowed free exchange of water vapour, trace gases and aerosols between the atmosphere and the snow. The control study for the influence of solar radiation on the snow-atmosphere exchange was identical to that of the bagged snow under open sunny sky except that it was carried out in the shade of an opaque fly sheet. The chemical composition and snow-water equivalent (SWE) of all bagged snows were determined before and after each experiment. The results from experiments at both sites show that solar radiation had no influence on show-atmosphere exchange of NO3 and SO4. In the first experiment at the forested site sublimation of water vapour from the snow occurred. The mass loss of water vapour was equally offset in sun and shade by significant increases in NO3 concentrations and no net loss or gain of this species by snow-atmosphere exchange thus took place. Changes in the concentrations of SO4 were not significant indicating that no dry deposition of this species had occurred. In the second experiment at the tundra site there was no loss of mass by sublimation. However in this case a significant net exchange of SO4 from the atmosphere to the snow with a dry deposition velocity of 0.09 cm/s was measured.
Keywords: Snowpack chemistry

Relationships between synoptic weather type frequencies and snowfall trends in the lee of lakes Erie and Ontario - Leathers, D.J.; Ellis, A.W. (61st Annual Western Snow Conference, 1993)
The relationship between synoptic weather type frequencies and snowfall trends in the lee of lakes Erie and Ontario is investigated. Large positive trends in monthly snowfall values are documented for the traditional snow belt regions for the period 1931 through 1990 for the month of January. The Temporal Synoptic Index (TSI) is used to identify synoptic patterns that are common to the eastern Great Lakes region during the snowfall season (November through March). The association between an individual synoptic pattern and snowfall is evaluated by consideration of basic meteorological principals. Results indicate that the positive snowfall trends in this region during the month of January are coincident with increasing frequencies of synoptic patterns found to be associated with lake-induced snowfall. Thus, secular variations of the large-scale atmospheric circulation are likely to be an important contributor to the observed positive trend in January snowfall in the snow belt region of the eastern Great Lakes. No relationship between variations in lake surface conditions and the snowfall trends are apparent.
Keywords: Synoptic patterns

The impact of heterogeneous flow paths on snowmelt runoff chemistry - Marsh, P.; Pomeroy, J.W. (61st Annual Western Snow Conference, 1993)
The role of heterogeneous flow paths in determining the chemical composition of meltwater was examined in a field experiment north of Inuvik, NWT. The concentration of major anions were determined for the pre-melt snowcover and for daily flow in 16 separate compartments within a 0.25 m² lysimeter. Daily melt water samples were retained for chemical analysis from four compartments representative of the total range of flows. Early in the melt period the daily flow volume varied from 0.2 to 2.5 times the daily mean flow for the entire lysimeter, while the solute concentrations were typically 2 to 5 times higher in the compartments with low flow than in those with the highest flows. The concentration factors (CF) [ratio of the solute concentration in the flow to initial snowpack solute concentration] early in the melt varied from 1.5 to 10, and then decreased to between 0.1 and 0.5 and after 50% of the melt there was no relationship between flow and concentration.
Keywords: Chemistry, Flow paths

An icing study for a future suspended bridge at Montmorency Falls - McComber, P.; Paradis, A. (61st Annual Western Snow Conference, 1993)
The site chosen by SÉPAQ (Société des établisenments de plein air du Québec) for a pedestrian bridge over Montmorency falls is particularly exposed to icing from droplet spray. ROCHE Ltd, responsible for the design of the bridge, has required a study to estimate the probable ice loads prior to the design of the suspended bridge.A 12.5 mm diameter steel cable was installed on existing towers at the location site of the future bridge. A load sell measured the end tension in the cable. Measurements of icing rate temperature, wind velocity and direction were also collected on site during the 1992-1993 winter, and compared with AES (Atmospheric Environment Service) meteorological data to establish an estimation valid over a longer period of time.Results have shown that a maximum 5 kg of ice collected can be attributed to droplet spray from the falls. In fact, two freezing events 4 and 22 January 1993, have resulted in glaze icing loads from atmospheric sources 3 to 4 times that amount. These results appear to be related to two factors. Firstly, most of the time the spray droplets do not appear to be in the supercooled state essential for their adhesion to the structure. Secondly, the random direction of the droplet cloud results in a low water content impinging locally on the cable. A numerical simulation has shown that in such a case the icing rate on a structure would be small and only very soft rime would form. This type of atmospheric icing would not constitute a hazard for the planned bridge.In conclusion, the additional icing due to the presence of the fall is small and therefore the design has been based on other estimated loads such as wind and glaze icing loads.
Keywords: Glaze, Ice loads, Icing, Rime, Snow loads

Identification and regional/spatial extent of rain-dominated winter storms in California's Sierra Nevada - McGurk, B.J.; Berg, N.H.; Kattelmann, R.C. (61st Annual Western Snow Conference, 1993)
A precipitation type index (PTI) was developed and tested on the record from two meteorological stations in California’s central Sierra Nevada that had visual classification of precipitation as rain, snow, or mixed types. The algorithm used new snowfall depth (S) and total precipitation (P), and was more accurate than classifications based on air temperature. The algorithm [PTI = (P x 100)/(P + S)] was applied to the records from several other mountain stations to identify rain-dominated storms, and to analyze the regional patterns of their magnitude and occurrence. Rain-dominated storms are more frequent, and of greater magnitude, on the north-central west slope of the range than in the south or to the east of the crest of the Sierra Nevada. Rain-dominated storms in the north-central portion of the range are most common during November. In the south and east, no single month dominated the temporal distribution of rain-dominated storms.
Keywords: Algorithm, Classification, Rain dominated, Snow dominated

Gridded snow water equivalent estimation using ground-based and airborne snow data - McManamon, A.; Szeliga, T.L.; Hartman, R.K.; Day, G.N.; Carroll, T.R. (61st Annual Western Snow Conference, 1993)
The National Weather Service (NWS) has developed a methodology to generate real-time gridded (1km) snow water equivalent estimates using ground-based and airborne snow data. The gridded snow water equivalents incorporate the spatial variability of the snowpack induced by orographic effects in the West. A baseline system is currently being implemented by the NWS over the Colorado River basin above Lake Powell.The Snow Estimating and Updating System (SEUS) uses a geographic information system (GIS) to store, analyze and display gridded, point and line data, such as elevation, basin boundaries and snow observations. The system has a calibration component to define basin-specific parameters, and an operational component to ingest real-time data and calculate gridded snow water equivalent estimates, and updating component to incorporate the ground-based snow water equivalent estimates into a conceptual hydrologic model. This paper reviews the system implementation and the results of operational testing during the 1993 snow season.
Keywords: GIS, Model, Snow cover

Snow sciences in North America - The Eastern and Western Snow Conferences in the context of environmental history - Mergen, B. (61st Annual Western Snow Conference, 1993)
The task of environmental history is ‘to deepen our understanding of how humans have been affected by their natural environment through time, and conversely and perhaps more importantly in view of the present global predicament, how they have affected that environment and with what results’ (Worster 1990, p. 1089). By looking at how snow has been described, defined, and classified and by asking how the study of snow fits into the larger cultural, scientific, and economic contexts of the past century, this paper offers an explanation of the significance of snow science in America today.
Keywords: Environmental history, Snow classification, Snow science significance

Snow depth mapping in Mongolia - Norton, D.C.; Bolsenga, S.J.; Badarch, M. (61st Annual Western Snow Conference, 1993)
The Great Lakes Environmental Research Laboratory (GLERL) has a cooperative program with Mongolian scientists to produce snow depth maps for that country. Snow depth data has been provided to GLERL. A raster data set was compiled from these data and preliminary maps produced. Since all stations are currently inside the country in valleys, the snow depths are not correctly projected across the country’s borders or over mountains. This progress report presents the preliminary maps and outlines the future course of the project. Information on locale, climate, people, customs, and problems with the study is also included.
Keywords: Snow depths

Cost analysis of snow control structures in Ontario - Perchanok, M.S.; Bacchus, A. (61st Annual Western Snow Conference, 1993)
The number of snow fences used along Ontario highways has declined as highway maintenance resources have diminished. This study was undertaken to compare alternative windbreak technologies to control drifting snow.Four principal types of windbreaks suitable for controlling snow were identified: 1) temporary snow fence, 2) permanent snow fence, 3) snow hedge, and 4) standing corn stalks when corn is planted in rotation, alternating with temporary snow fence in other years.Material, labour and land costs associated with each type were estimated, and compared on the basis of equivalent annual cost of the net present value, for periods ranging from 1 to 50 years.Where practical, corn stalks with temporary snow fence was the lowest cost alternative for periods from 1 to 6 years. Permanent snow fence was the lowest cost alternative for longer periods. The study showed that permanent snow fence or snow hedge are more cost effective than temporary snow fence inn controlling drifting snow and should be considered for installation where land-use conditions are suitable.
Keywords: Snow control, Snow fences, Windbreaks

Hydrochemistry of snowmelt at Rabbit Ears Pass, Rocky Mountains, Colorado - Peters, N.E.; Leavesley, G.H. (61st Annual Western Snow Conference, 1993)
The chemical composition of snowmelt from ridge-top lysimeters, groundwater along a hillslope transect, and streamwater at the basin outlet was monitored during the spring of 1991 and 1992 in a 2-km² subalpine catchment on the western flank of the Rocky Mountains near Steamboat Springs, Colorado. Most of the snowmelt occurred during two-month periods that began in mid May 1991 and mid April 1992. The solutes in the meltwater were differentially eluted from the snowpack in each year and the meltwater was dominated by Ca(2+) and Mg(2+) and the acid anions, SO4(2-) and NO3(-); the concentration sum of Ca(2+) and Mg(2+) was equal to the sum of SO4(2-) and NO3(-).The composition of groundwater and streamwater was dominated by weathering products, such as Ca(2+), HCO3(-) (measured as alkalinity), and dissolved SiO2, and their concentrations decreased as snowmelt progressed. The SO4(2-) and NO3(-) concentrations of groundwater generally were higher than those of meltwater. In particular, groundwater from one well in the mid-slope position, which was at the highest elevation sampled, had extremely high NO3(-) concentrations during snowmelt in both years. These high NO3(-) concentrations were balanced by Ca(2+) concentrations. As snowmelt progressed, NO3(-) and Ca(2+) concentrations in groundwater decreased, consistent with dilution by meltwater from the snowpack.Solute concentrations in streamwater also decreased as snowmelt progressed. The NO3(-) concentrations decreased more rapidly than did SO4(2-) concentrations. These results indicate that some of the SO4(2-) and NO3(-) in streamwater was derived from sources other than the snowpack, or that the meltwater composition on other drainages was more concentrated with respect to other constituents. Also, the relative changes in the SO4(2-) and NO3(-) concentrations of streamwater indicate that different processes control their mobility.
Keywords: Chemistry, Groundwater, Snowmelt, Water quality

The use of fractual geometry in modelling intercepted snow accumulation and sublimation - Pomeroy, J.; Schmidt, R.A. (61st Annual Western Snow Conference, 1993)
In the boreal forest, interception of snow can store 60% of cumulative snowfall in mid-winter and sublimation of this snow can return over 30% of annual snowfall to the atmosphere as water vapour. A sublimation algorithm for a single ice sphere and an ‘exposure coefficient’ which accounts for the difference in surface area to mass ratios between intercepted snow and the ice sphere permit calculation of the sublimation rate in coniferous canopies. Fractal geometry provides a tool to calculate this exposure coefficient from digitised photographs of snowcovered canopies. Intercepted snow is fractal and the irregularity of its shape depends on locaton in the canopy and age of the snow. The fractal shape of intercepted snow permits a relationship between snowcovered area in canopy photographs and interception load. The analysis shows the feasibility of a physically-based model of intercepted snow accumulation and sublimation that uses standard meteorological measurements and digitised photographs of the canopy.
Keywords: Fractuals, Interception, Modelling, Sublimation

proposed artifical river ice damming to induce flooding of a delta ecosystem - Prowse, T.D.; Demuth, M.N.; Peterson, M. (61st Annual Western Snow Conference, 1993)
Over the last twenty-five years, significant ecological changes have occurred in the Peace-Athabasca Delta largely because of changes in the hydrological regime of the Peace River, including flow regulation. Spring floods historically inundated the delta and supplied the major input to the water balance of many of the perched basins. No flooding of these basins, however, has occurred since 1974 despite historically high flows on the Peace River. As a result of long-term drying, there has been a significant reduction in wetlands and meadows and an invasion of more persistent shrub communities. Recent recognition that ice jams on the Peace River were the only way in which flooding of the perched basins could have occurred, a project has been initiated to flood these basins through the creation of artificial ice dams. An initial trial using surface-flooding was attempted in late-winter of 1993. Although the cover thickness was augmented no flooding occurred. Future plans are to employ spray-ice technology which should permit more rapid ice growth and a greater obstruction of the total flow depth.
Keywords: Dams, Deltas, Flooding, Ice jambs

The developing moderate resolution imaging spectroradiometer (MODIS) snow cover algorithm - Riggs, G.; Hall, D.; Salomonson, V.; Barker, J. (61st Annual Western Snow Conference, 1993)
Elements of the snow cover algorithm to be implemented with the Earth Observing System (EOS) MODerate resolution Imaging Spectroradiometer (MODIS), scheduled for launch in 1998, are being developed and tested. The MODIS snow cover algorithm utilizes unique spectral and spatial characteristics of the MODIS to identify snow by reflectance characteristics. The algorithm implements a series of criteria tests and a Normalized Snow Difference Index (NSDI) to identify snow and to discriminate snow from many types of clouds. Landsat Thematic Mapper (TM ) data, simulated MODIS data, and Advanced Very High Resolution Radiometer (AVHRR) data are used to prototype the algorithm. The snow cover algorithm has been tested on a variety of Landsat TM scenes with consistent snow identification results.
Keywords: Algorithm, AVHRR, EOS, Satellite, Snow cover

Associations between snow cover extent and surface air temperature over North America - Robinson, D.A.; Leathers, D.J. (61st Annual Western Snow Conference, 1993)
We find significant associations between regional snow-cover extent and surface air temperature across North America. In a large majority of cases when the extent of snow cover is above normal, temperature departures are negative. Conversely, negative snow departures are almost always associated with above normal temperatures. Regional correlations are highest in seasons when snow cover is most variable. The largest temperature departures are associated with anomalies of snow cover over the central portion of the continent. An examination of 500 mb heights across North America suggests that – though circulation anomalies doubtlessly contribute to the temperature departures observed in regions of anomalous snow – the presence of absence of snow strongly influences temperatures. This relationship is most apparent in situations of above average snow extent. Results of this investigation should be of interest to those studying middle and high-latitude climate dynamics and climate change from both an empirical and modeling perspective.
Keywords: Climate change, Snow cover

Interactive calibration for the SSARR watershed model - Rockwood, D.M.; Kuehl, D.W. (61st Annual Western Snow Conference, 1993)
This paper illustrates an improved, efficient method for calibrating the watershed portion of the Streamflow Synthesis and Reservoir Regulation model (SSARR). This is made possible by the recent advances in the personal computer (PC) version of the model, together with advances in the new highly developed personal computers.Calibrations are performed interactively within the framework of the SSARR data processing system, operating under an MS-DOS environment. The system provides generalized parameter functions, water balance determinations, statistical error evaluations, and graphical screen displays of results.
Keywords: Calibration, Model, SSARR

Improving estimates of snowpack water equivalent using double sampling - Rovansek, R.J.; Kane, D.L.; Hinzman, L.D. (61st Annual Western Snow Conference, 1993)
Equations are presented to estimate the average water equivalent of a snowpack and the variance of this estimate using double sampling. Double sampling refers to sampling the snowpack in two ways: measuring the depth at a number of points, and measuring the depth and the water equivalent at a smaller number of points. In a given sampling interval, doubling sampling can yield an estimate of snowpack water equivalent having a lower variance than is possible by measuring water equivalent only. The equations presented in this paper were tested during extensive snow surveys conducted on the North Slope of Alaska. The snowpack of the North Slope is similar to that of the Great Plains, thin and variable in both depth and density due to extensive redistribution of snow by wind. This variability makes estimation of an area difficult, and provides a rigorous test of the equations presented here.Two two-hour snow surveys conducted by sampling water equivalent only, and be sampling both depth and water equivalent yielded identical estimates of water equivalent (48.1 mm). However, the double sampling estimate had a variance of only 80% of the variance of the estimate using water equivalent only (4.9 mm² vs. 6.1 mm²). Equations are also presented for calculating the optimal ratio of depth to water equivalent measurements. By considering time as the only cost of collecting the two measurements it is possible to calculate the ratio of depth to water equivalent measurements that will result in the best estimate of average snowpack water equivalent in a given sampling time. The optimal ratio of depths to water equivalent measurements varies between individual surveys, so times measured during snow surveys in a number of different locations and snow conditions on the North Slope were used to estimate a regional optimal ratio of depth to water equivalent measurements of about 14 to 1.
Keywords: Double sampling, Sampling, Snow surveys, SWE

An automated quality control procedure for the water equivalent of snow on the ground measurement - Schmidlin, T.W.; Wilks, D.S.; Cember, R.P. (61st Annual Western Snow Conference, 1993)
Snow water equivalent (SWE) has been measured daily by the United States National Weather Service since 1952 whenever show depth is 5 cm or greater. These data are used to develop design snow loads for buildings, for hydrological forecasting, and as an indicator of climate change, but have not been subjected to quality control. The quality control procedure developed here for the northeastern United States checks daily SWE measurements for common digitizing errors, values beyond reasonable limits, and consistency with daily precipitation and melt. Potential effects of drifting and the intrinsic micro-scale variability of SWE are also considered. A daily SWE measurement is declared suspicious if a sufficient discrepancy is found between the measurement and the expected SWE. Data flagged as errors are checked manually.
Keywords: Errors, SWE

Application of SAR snowcover mapping to hydrological modeling of snowmelt runoff in Southern Ontario - Seglenenieks, F.; Soulis, E.D.; Kouwen, N.; Donald, J.R. (61st Annual Western Snow Conference, 1993)
In this experiment WATFLOOD, a distributed hydrologic model, was set up for the 1991 spring snowmelt event on the Grand River watershed to investigate the possibility of using airborne nadir C-band Synthetic Aperture Radar (SAR) imagery to update the model by providing snow covered area (SCA) information. WATFLOOD parameters were first derived using only atmospheric and ground data, the model was then run again to derive parameters using the SAR imagery to update the model. The results showed that model appeared to simulate the river flow better when updated using the SAR imagery. It was concluded that the present WATFLOOD optimization, which deals solely with river flows, allows for unrealistic values for snowmelt. This can be corrected by separate optimization of snowmelt parameters to known snow cover characteristics and of snowpack hydraulic characteristics to streamflow.
Keywords: Modeling, Radar, Snow cover

Geometry of patchy snowcovers - Shook, K.; Gray, D.M.; Pomeroy, J.W. (61st Annual Western Snow Conference, 1993)
The influence of spatial variation in snowcover water equivalent on areal snow-cover depletion and the geometry of snow patches that form during the ablation of shallow, seasonal snowcovers in open environments is discussed. A simplified snowpack ablation simulation is used to demonstrate that the fractal structure of the snowcover water equivalent causes soil and snow patches to possess fractal characteristics. This program is a distributed, grid-square model that uses a synthetically-generated snowcover and includes an algorithm for approximating the effects of local advection on melt. Fractal dimension(s) of snow patches produced by the model are shown to agree closely with the dimensions of natural ablated snowcovers determined from analyses of aerial photographs.
Keywords: Ablation, Fractals, Grid-square, Model, Snow cover

Stress analysis of a proposed tunnel underr the South Pole skiway - Sodhi, D.S.; Rand, J.H.; Tobiasson, W. (61st Annual Western Snow Conference, 1993)
Unlined tunnels in the snow at the South Pole Station will be used for save movement of personnel to satellite science buildings during the austral winter. The first 1.8 m (6 ft) wide, 3 m (10 ft) high tunnel will pass under the existing skiway. This study determined the depth at which that tunnel should be located so that it is safe when aircraft pass over it. Three efforts were undertaken: (a) conducting a three-dimensional, elastic stress analysis of the snow around the tunnel, (b) comparing the maximum tensile and shear stresses from that analysis with corresponding strengths published in the literature, and (c) performing two experiments at the South Pole to determine the surface pressure required to fail the snow around model tunnels. We found general agreement of theoretical and experimental results and recommended that the roof of the tunnel be located at least 6.1 m (20 ft) below the surface of the skiway.
Keywords: Snow loading, Strength test, Stress, Tunnels

Seasonal snowfall totals to 1992-1993 from 1884-1885 for Oswego, New York - Sykes, R.B. Jr. (61st Annual Western Snow Conference, 1993)
Continuous monthly snowfall information started with the 1884-85 snowfall season. During this 109-year period measurements have been made from at least 9 locations within, and near Oswego City. Interpretation of snowfall data is complicated not only by the number of reporting sites, but also by varying methods of measurement, and by wide variations in snowfall conditions due to high percentages of lake-effect episodes. Space limitations require that this paper concentrate on this 109-year period, Table 1, and on the selection of some recent seasons, Table 2, for brief special comment. Four photographs by the author illustrate typical conditions (Figures 1-4). Dedications and acknowledgments comprise the final text section.
Keywords: Historical records

Selection of the winter representative precipitation station within a basin - Takenouchi, T. (61st Annual Western Snow Conference, 1993)
The shape of Japan is a narrow island and stretches from southwest to northeast. In winter, the wind blows from northeast to southeast. The humid wind which absorbs the high humidity while passing the Sea of Japan, which it releases as snow as it encounters the high mountains.Here we discuss the case where there is some amount of snowfall in the southern part of the topographic divide. We can estimate the depth of spring runoff from the depth of winter accumulated snow at selected station.We estimated a ‘model’ representing the shape of the land where there is a valley in the northern part, intervening the topographic divide, and a small river basin in the southern part.In the model, a good correlation can be found between the depth of winter accumulated precipitation at the selected station and the depth of runoff at the dam site.
Keywords: Location, Orographic effects, Precipitation gage

Partitioning the deposition of winter snowfall as a function of aspect on forested sites - Troendle, C.A.; Schmidt, R.A.; Martinez, M.H. (61st Annual Western Snow Conference, 1993)
Snowpack accumulation, expressed as Peak Water Equivalent (PWE) is usually least and peaks earliest on south facing slopes. This study, conducted as part of an ongoing effort to define snow deposition and ablation processes, attempted to partition the components in the deposition process that could result in the differences in PWE. Total flux into the canopy on opposing north and south facing slopes was found to be similar, although some difference in particle size at interior canopy positions occurred. Ventilation, or windspeed within the canopy, was greater on the south slope. Throughfall (storm basis) was equal on both slopes but accumulation on the south slope lagged behind that on the north slope. The initial lag was attributed to evaporative differences. In March, melt on the south slope was more significant. The south slope had 7.7 cm less water equivalent than the north slope on April 1. One third of the difference was attributed to melt, two thirds to greater vaporization.
Keywords: Sublimation

Hierarchic studies of snow-ecosystem interactions - a 100-year snow-alteration experiment - Walker, D.A.; Lewis, B.E.; Krantz, W.B.; Price, E.T.; Tabler, R.D. (61st Annual Western Snow Conference, 1993)
The Niwot Long-Term Ecological Research (LTER) project is examining the long-term ecological effects of altered snowpack regimes. Key components of the studies include: (1) hierarchic analysis of the relationship between natural snowpack patterns and geobotanical features, and (2) a snow fence experiment. A 3-m high snow fence will be built in the summer of 1993. Baseline soil temperature and snow-depth studies were initiated during the unusually wet winter of 1992-93 (183% of normal precipitation at the D-1 climate station on Niwot Ridge). Minimum winter soil temperatures (15-cm depth) were about -10deg C.
Keywords: Ecology, Snow fencing

Snowpack storage and release of nitrogen in the Emerald Lake Watershed, Sierra Nevada - Williams, M.W. (61st Annual Western Snow Conference, 1993)
Interactions between the storage and release of nitrogen (N) from the seasonal snowpack and basin processes were evaluated from 1985 through 1987 at the Emerald Lake Watershed, located at 2800 m in the southern Sierra Nevada, California. The volume-weighted mean annual concentrations of NH4(+) and NO3(-) in winter snow were <= 5.0 µeq/L and are among the most dilute recorded in the northern hemisphere. However, about 90% of the annual flux on NH4(+) and NO3(-) in wet deposition was supplied during the period of snowmelt runoff, due to the large percentage of annual precipitation that occurred as snow. Dry deposition in N to the seasonal snowpack was not significant relative to wet deposition. Concentrations on NH4(+) and NO3(-) in the first fraction of meltwater were 3-6 fold greater than bulk concentrations measured in co-located snow pits, an ionic pulse. Elution of NO3(-) from the snowpack in the form of an ionic pulse appeared to be the cause of seasonal maxima in NO3(-) concentration in stream waters. In contrast to the export of NO3(-) during snowpack runoff, more than 99% of the ammonium stored in the seasonal snowpack was retained in the basin. The retention of NH4(+) in the basin during snowpack runoff indicates that much of snowpack meltwater infiltrates soils before becoming stream water and that soil processes with relatively fast kinetics must be active at this time.
Keywords: Chemistry, Snowpack chemistry

True Snowfall -- An evaluation of the double fence intercomparison reference gauge - Yang, D.; Metcalf, J.R.; Goodison, B.E.; Mekis, E. (61st Annual Western Snow Conference, 1993)
Based on the analysis of WMO intercomparison data from 1970 through 1990 at the Valdai Hydrological Research Station in Russia, this study found that blowing snow occurred during one-third of the snowfall events greater than 3.0 mm. Wind direction during these events was primarily from the south where a small lake is located. After eliminating the snowfall events during which blowing snow occurred, there remains a systematic difference between the measurements of the bush gauge and the Double Fence Intercomparison Reference (DFIR) gauge, that is, the bush gauge catches more snow than the DFIR. Therefore the correction of the DFIR for wind induced loss is necessary in order to best represent true precipitation. Regression analysis indicates that the most important factor to the correction is mean wind speed during the storm. Correction equations for different types of precipitation have been developed. An example of the application of using the DFIR as a reference standard is demonstrated with two typical North American precipitation gauges.
Keywords: Blowing snow, Gauge corrections, Snow gage, Snow gauge

1992 Title, Contents, and Minutes (60th Annual Western Snow Conference, 1992)

Monitoring snow grain size for passive microwave studies - Armstrong, R.L.; Rango, A. (60th Annual Western Snow Conference, 1992)
The application of passive microwave radiometry to the remote sensing of snow properties is based the ratio of emitted to scattered portions of the upwelling radiation. Increased scattering is indicative of increased snow amount (i.e., the number of snow grains present). However, scattering is directly proportional to snow grain size for a given snow amount. Current snow cover retrevial algorithms produce inaccurate results when snow grain size are unusually large. Therefore, it is necessary to characterize snow grain size on a regional scale (and perhaps a local scale in extreme situations) in order to adjust passive microwave retrieval algorithms. Preliminary analysis indicates that: (1) retrieval algorithms are not as sensitive to grain size as theory would indicate; (2) average grain size data may serve to characterize the detailed stratigraphy of the total snow cover, and; (3) conditions in subfreezing snow which produce cover-climate relationships which can be modelled or monitored on a regional scale.
Keywords: Passive microwave radiometry, Snow grain size, Upwelling radiation

Where has all the snow gone? Snowpack sublimation in northern Utah - Avery, C.C.; Dexter, L.R.; Wier, R.R.; Delinger, W.G.; Tecle, A.; Becker, R.J. (60th Annual Western Snow Conference, 1992)
Climatic data for twenty-one winters was used to construct an index to assess the significance of evapo-sublimation at Flagstaff, Arizona. Large intra- and inter-annual variability was noted in the record using this 'sublimation opportunity index' as well as a similar one based on ('corrected for') the presence of snowcover.An instrument to record evapo-sublimation has been developed and preliminary data is presented which compares values from this 'sublimimeter' to the index values for periods in 1990-91 and 1991-92.While the index is not a predictive model, relatively good (R2 = 0.62, cross-correlation coefficient = 0.89, cross association value = 79%) agreement is found between index values and the observed values.It appears that at least 22% and as much as 70% of the snowpack at this high elevation site may be lost to sublimation and, therefore, that the date of snowpack accumulation is critical to the runoff efficiency of high elevation snowpacks.
Keywords: Evapo-sublimation, Sublimation opportunity index, Sublimimeter

A GIS-based method of modeling water input from rain-on-snow storms for management and regulation of clearcut forest harvest - Brunengo, M.J.; Smith, S.; Bernath, S.C. (60th Annual Western Snow Conference, 1992)
Timber harvest has helped transform the Northwest into a patchwork of cities, farms, clearcuts, plantations, and mature trees, surrounding fragments of primeval forest. Forest canopy affects snow accumulation and melt, particularly during rain-on-snow storms; harvest has thus caused changes in water systems at various scales. The management environment has also changed, with increased attention to protection of woodland resources.DNR now regulates harvest with regard to water input during R/S events. The key layer of our GIS-based system is a map of precipitation zones, based on snow available for melting (used partly to determine which forest-practice applications are examined for R/S implications). Modeling of snowmelt during hypothetical events allows estimation of water reaching the soil in each polygon. Differences between inputs under fully-forested and current vegetation suggest changes in effective storm frequency. Results are used to predict hydrologic effects of harvest scenarios.
Keywords: Harvest, Precipitation zones, Rain-on-snow storms

Expanding SCS's remote sensing program - Cooper, P.D.; Werner, J.G.; Schaeffer, G. (60th Annual Western Snow Conference, 1992)
The Soil Conservation Service (SCS) is involved in an effort to expand it’s application of meteor burst communications from Western water supply forecasting into other resource management concerns. A pilot site was installed in Sherburne County, Minnesota, in May 1990. Local SCS offices have begun utilizing the site’s meteorological data for Evapotranspiration (ET) estimates. These ET estimates are made available to landowners for irrigation scheduling. The irrigation scheduling program is part of an SCS/Extension Service Water Quality Demonstration Project aimed at reducing nitrogen loading to groundwater in the Anoka Sand Plain area.Beginning August, 1991, the Minnesota site, along with ten other new installations east of the Rockies were equipped with meteorological and soil moisture and soil temperature sensors. This newest phase in SCS resource inventory operations is aimed at demonstrating the (etc.)
Keywords: Climatic data, Global change, Meteor burst, Remote sensing, SNOTEL, Water quality

40 years snow cover measurements in France - Duband, D.; Lallement, C. (60th Annual Western Snow Conference, 1992)
For nearly 40 years, EDF (French National Electricity Board) has been using a snow survey network in order to forecast snowmelt inflow for the purpose of water management (hydropower optimization, agriculture, water-sports...) during the end of winter, spring and summer. This network, set up at altitudes between 800 m and 2700 m consists of 240 manual gauging sites (having dropped from 650 in the late 60’s), in Alps - Pyrenees - Central range mountains.Meanwhile, in order to get real-time data, EDF has developed an original automatic level gauge service: the 'TELENIVOMETER'. This equipment can measure, once a day or more, the density of different layers of snow (10 cm slices) the snowdepth and the air temperature and thus deduces the water equivalent. The data can be collected by satellite (ARGOS) or by telephone for lower-altitude sites.
Keywords: France, Multipurpose water management, Snow cover measurements

Simulation of snowmelt in a small rangeland watershed - Flerchinger, G.N.; Cooley, K.R. (60th Annual Western Snow Conference, 1992)
Snowmelt simulation of the Simultaneous Heat And Water (SHAW) model was tested by applying the model to two years of data from three sites on a rangeland watershed ranging from transient snow cover on a west-facing slope. The SHAW model is a point energy and mass balance model and simulates a one-dimensional profile extending from the snow, residue or soil surface to a specified depth within the soil. The model’s ability to simulate heat and water movement through plant cover, snow, residue and soil has been demonstrated, but the accuracy of the model in predicting snowmelt outflow has never been tested. The timing and magnitude of simulated hourly and daily snowmelt compared well with measured values. Results suggest that the SHAW model can be applied successfully to predict snowmelt from diverse rangeland sites.
Keywords: Energy balance, Hydrologic modeling, Snowmelt modeling

An improved carrying case for snow tubes - Gluns, D.R.; Rose, G. (60th Annual Western Snow Conference, 1992)
The need by snow surveyors and researchers to travel to remote snow sites by skis, snowshoes or snowmachines necessitates carrying snow tubes and survival equipment. This paper describes a new pack for carrying snow measuring equipment along with personal survival gear in a comfortable fashion and still offer protection for the equipment. The snow tube portion of the pack is removable for summer storage and allows for the main portion of the pack to be used year round. First season field use of the pack is reported and input before commercial production is solicited.
Keywords: Pack, Snow tubes

Snow surveying comes of age in the west - Helms, J.D. (60th Annual Western Snow Conference, 1992)
The Bureau of Agricultural Engineering’s coordination of snow surveying activity was transferred the Soil Conservation Service in 1939 along with several other operations of the bureau’s divisions of irrigation and drainage. The move linked the snow survey operations with an agency which worked directly with many of the main clients of snow survey--the irrigation farmers.This paper recounts the growth of water supply forecasting in the 1930’s and 1940’s with special emphasis on the snow survey network, publicity, concerns about the accuracy and improvement of forecasts, and uses of water supply forecasts including its value for predicting floods.
Keywords: SCS field staff, Snow survey coordination, Water supply forecasting growth

Environmental influences on snow algal microbes - Hoham, R.W. (60th Annual Western Snow Conference, 1992)
Microbes called snow algae are worldwide in their distribution from alpine and polar environments. These microbes have been reported from 13 western states during the time of snowmelt. They occupy extreme conditions of cold temperature acidified snow, high irradiation levers and minimum nutrients for growth during snowmelt and summer drought after snowmelt. Snow algae color the snow green, orange or red, and environmental factors influence the distributions of individual spedies. A recent study of red snow from Wyoming and red and green snow from Antarctica shows differences in pigment ratios, fatty acid ratios and total nitroben content. In another study closely related snow algae from the White Mtns. Arizona and the Adirondacks,N.Y., appear to have lost their capacity to reproduce sexually, but several observations of abnormal sexual reproduction have been observed. These reproductive strategies may be important for the survival of snow algae in the natural environment.
Keywords: Algae, Ecology, Microbes, Physiology, Snow microbes

Harvesting snow when water levels are low - Jairell, R.L.; Schmidt, R.A. (60th Annual Western Snow Conference, 1992)
Designing a snow fence-pit-berm water source for livestock of wildlife on the High Plains begins by estimating available snow transport, from average winter snowfall and fetch distance along the drifting wind direction. Pit excavation must match this volume of water. The pit will then trap one-half the snow transport. A snow fence height is chosen to provide storage for the one-half of snow transport not stored in the pit. The snow fence, pit, and berm are extended across the wind to match the water requirements (number of animals, number of days of use). Cost is less than most wells with pumping systems.
Keywords: Fence-pit-berm, High plains, Livestock water supply, Water source

Predicting snow melt and streamflow volumes in the Arkansas River Basin of Colorado - Kickless, R.C. (60th Annual Western Snow Conference, 1992)
The National Weather Service (NWS) and United States Geological Survey (USGS) are conducting a cooperative study to predict snowmelt in the Arkansas River Basin of Colorado. Extended Streamflow Prediction (ESP) is being used to model the study area. ESP combines statistical frequency analysis with conceptual computer modeling to produce probability forecasts. Observed historical streamflow, simulated historical streamflow, and conditional simulated streamflow, and conditional simulated streamflow are used to develop probability distributions for each data type.Inflow volumes are being predicted for Pueblo Reservoir, Colorado during the spring and summer runoff periods. These volumes will be used by the U.S. Army Corps of Engineers to maximize reservoir storage. A comparison is being made between NWS-Soil Conservation Service Water Supply Forecasts and Extended Streamflow Prediction at selected water supply forecast points.
Keywords: Frequency analysis, Inflow volumes, Predict snowmelt

Applying a climatic change scenario to a semi-distributed watershed model - Kite, G. (60th Annual Western Snow Conference, 1992)
Atmospheric general circulation models (CGMs) predict major changes in the earth’s climate due to an expected doubling of atmospheric greenhouse gases such as CO2. Watershed models have been used to estimate the effects of the changed climate on water resources but these models have generally assumed that the watershed itself will remain unchanged. It is more likely that a changing climate will change the distribution and the transpiration efficiency of vegetation. A semi-distributed hydrological model was applied to a watershed in the Rocky Mountains of British Columbia. The watershed was divided into a number of sub-basins and each sub-basin was divided into land-use zones. The paper discusses the methods available for linking the output of the GCM to the watershed model and discusses the results of the application in terms of the model responses.
Keywords: Climate change, Watershed models

Snow-fall event climatology: The finale - Mahoney, J.L.; Brown, J.M. (60th Annual Western Snow Conference, 1992)
Two distinct types of snowfall events that produce heavy snow along the Front Range of Colorado are discussed in Part 2 of the snowfall-event climatology. A 40-year snowfall-event archive was used as the basis for the study. The additional analyses of synoptic surface and upper air maps, soundings and quasi-geostrophic diagnostics led to the identification of two distinct synoptic patterns, which we shall refer to as a Four Corners Low and a Southeast Colorado Low.The Four Corners Lows were characterized by surface high pressure of arctic regions to the north of Colorado with a cyclone to the southwest of the state, shallow upslope below 700 mb capped by an inversion layer with southwesterly winds above, and lack of synoptic-scale forcing of vertical motion. The Southeast Colorado Lows featured an intense surface cyclone over the southern High Plains associated with a strong upper trough or closed low, deep upslope flow over northeast Colorado, a jet from the northeast quadrant 750 and 500 mb, and strong vertical coherence in the synoptic-scale forcing of vertical motion. We will present examples of each synoptic.
Keywords: Climatology, Colorado winter storms, Snowfall event, Synoptic scale patterns

Propylene glycol and ethanol: A replacement for glycometh as an antifreeze in precipitation gauges - McGurk, B.J. (60th Annual Western Snow Conference, 1992)
Federal and state agencies have used a 40 percent ethylene glycol-60 percent methanol solution (glycometh) as an antifreeze solution in precipitation gauges for over 25 years. Current and future disposal regulations, however, make the continued use of the toxic glycometh unfeasible. Propylene glycol (PG) and denatured ethanol have been identified as likely substitutes for glycometh because they have similar characteristics but have low toxicity levels. This paper reports on cold room experiments (0 to -40 degrees C) to ascertain the freezing point of five different mixing ratios of PG and ethanol (PGE) in ten dilutions (1:0 to 1:7) with water. Little difference in freezing point was found across the five mixing ratios, so solution density and cost are important in recommending the best mixing ratio. An equation combines factors such as annual precipitation and minimum January temperature to predict the quantity of PGE that is required as a 'charge' at a precipitation gauging site.
Keywords: Ethylene glycol, Freezing point, Methanol, Solution density, Toxic glycometh

Estimation of 30 year average annual precipitation for SNOTEL sites in Idaho - Morrisey, P.S. (60th Annual Western Snow Conference, 1992)
The Soil Conservation Service (SCS) operates and maintains a network of 69 automated SNOTEL (SNOw TELemetry) sites in Idaho. Most have a continuous daily precipitation data record from 1982. 1961-1990 average annual precipitation (AAP) was estimated for 65 of the sites having more than five years of data using simple linear regression. Water year annual precipitation for the available years was compared to nearby national Weather Service (NWS) stations. Up to 14 NWS stations were analyzed for each SNOTEL site. The three highest correlating NWS sites for each SNOTEL site were selected and the 1961-1990 AAP at the NWS sites was used to estimate three 30 year AAP values for each SNOTEL site from the regression equations. The final 1961-1990 AAP for the SNOTEL sites was the mean calculated from the three individual values. High correlations were consistently obtained between SNOTEL and NWS annual precipitation.
Keywords: 30 year average annual precipitation, Daily precipitation, SNOTEL sites

Minimizing Measurement Errors in Automated Snowpack Profile Temperature Measurements - Sauter, K.A.; Tanner, B.D. (60th Annual Western Snow Conference, 1992)
Snowpack profile temperatures were measured hourly during the winter season in the Bear River Mountains of northern Utah. A monofilament fish line ladder was constructed to support 20 junction chromel-constantan (Type E) thermocouple (TC) string in the snowpack. To minimize conductance, 0.25 mm TC wire was routed along the ground surface, up and horizontally across 10 cm spaced ladder rungs. Hourly, a datalogger measured each TC junction 10 times and calculated an average temperature.During the season, a maximum cavitation of 1 cm in diameter and 2 in depth was observed around the mono-filament support structure. Under isothermal conditions (Tsnow = 0 degrees C), TC temperatures were within +0.05 C of 0.0 C. Effects from surface conductance was evident in upper snowpack temperatures to an approximate depth of 20 cm.
Keywords: Snowpack profile temperatures, Thermal conductance, Thermocouple

Prediction of snowmelt rates at a forested alpine site in northern Utah - Sauter, K.A.; McDonnell, J.J. (60th Annual Western Snow Conference, 1992)
This study examined snow surface energy exchanges in the forested Bear River mountains of northern utah. The site was located at Beaver Mountain (2600 m) on a northeast aspect slope and instrumented to measure net radiation, incoming and reflected shortwave radiation air temperature, soil temperature, snow temperature, relative humidity, wind gradients, snow temperature, relative humidity, wind gradients and direction, snow depth, and percipitation. Measurements were taken every 30 seconds and averaged over 30 minute intervals. The data was transmitted daily 32.9 km to Logan, Utah, via radio telemetry.Strong winds and warm, humid air preceded frontal weather systems passing over the Bear River mountains. Nevertheless, maximum daily average recorded wind speed was only 1.6 m/s, and the mean daily average was just 0.57 m/s. Snow surface energy exchanges were determined by bulk aerodynamic equations. Low momentum exchange resulted in net radiation dominating the surface energy budget. (etc.)
Keywords: Energy exchange, Melt season, Net radiation, Snow surface

Sublimation of intercepted snow as a global source of water vapour - Schmidt, R.A.; Troendle, C.A. (60th Annual Western Snow Conference, 1992)
Considering the vapor loss from grains on the snow surface produced a model to predict the sublimation rate of snow intercepted on conifer branches. Experiments to test this model showed that the controlling environmental factors, temperature, humidity, radiation, and wind speed, were properly accounted for. These results, combined with other experiments on the redistribution of snow by wind, show that most of the water increase associated with timber harvest in snow country may be attributed to reduced sublimation losses. If so, then up to a third of snowfall may return directly to the atmosphere from forest canopies. The paper compares the significance of timber harvest with climate change in influencing the magnitude of this component of the global water balance.
Keywords: Global water balance, Redistribution, Sublimation

Snow management in the reclamation of sodic soils - Steppuhn, H.; Curtin, D. (60th Annual Western Snow Conference, 1992)
Sodic soils contain an excess of exchangeable sodium relative to other captions. This imbalance together with other conductive conditions cause soil aggregates to separate into smaller particles, alter the soil structure, restrict infiltration, and reduce permeability. Reclamation of sodic soils often includes the application of calcium amendments to displace and free the sodium for subsequent leaching. When irrigation water is unavailable, the rate of the reclamation depends on natural precipitation. Snow management to increase water quantities for these Ca-amended soils might facilitate and accelerate reclamation.A trial in Saskatchewan using plastic snow fencing erected on small plots demonstrated that snow management practiced on highly sodic soil amended with Ca can improve water intake. Snow fenced plots accumulated water equivalents seven-fold greater (76 to 11 mm) than comparable unfenced plots. Upon melting, this snow cover enhancement supplied 41% more water and to deeper within the soil profile to 60 cm.
Keywords: Calcium ammendments, Sodic soils, Sodicity, Soil reclamation

Snowpack loss component for a water budget model using a Geographical Information System for the San Juan Aquifer Basin in New Mexico and Colorado - Waltemeyer, S.D.; Kernodle, J.M. (60th Annual Western Snow Conference, 1992)
A water budget model was applied to the San Juan basin aquifer New Mexico and Colorado. Direct recharge was estimated at the mouth of 272 surface basins. Mean annual winter precipitation for each surface basin was weighted upon the respective basin area and the isoline intersecting each basin using a Geographical Information System (GIS). Overall winter precipitation component was estimated at 8,600 cubic feet per second for the aquifer basin.Mean annual discharge for three distinct physiographic regions were used to estimate the streamflow component. The overall streamflow component was estimated at 2,670 cubic feet per second for the aquifer basin.A snowpack loss component was determined from a relation of April 1 water content and a corresponding relation of average basins mean annual winter precipitation. The snowpack loss component was derived.
Keywords: DEM, Physiographic regions, Streamflow components, Water budget

Hydrologic flowpaths of snowpack runoff in a high-elevation catchment - Williams, M.W. (60th Annual Western Snow Conference, 1992)
High-elevation basins will show hydrologic and hydrochemical effects from global or regional climate change much sooner than will basins located at lower elevations. The combination of small hydrologic storage in groundwater reservoirs, the predominance of intrusive igneous rocks that weather slowly, the thin acidic soils, large amount of precipitation, and low buffering ability of alpine basins result in high-elevation areas of the Sierra Nevada responding quickly to changes in the quantity and quality of precipitation. In particular, global or regional climate change may increase both the magnitude and frequency of floods from snowpack runoff. Hydrologic and hydrochemical effects of snowpack runoff are a function of the path water takes as it leaves the snowpack and moves towards surface waters. It is essential to understand hydrological flowpaths in high-elevation basins if we are to forecast the hydrologic and hydrochemical consequences of a changing climate.
Keywords: Global climate change, High-elevation basins, hydrochemical effects, Regional climate change

1991 Title, Contents, and Minutes (59th Annual Western Snow Conference, 1991)

Monitoring global snow cover - Armstrong, R.L. (59th Annual Western Snow Conference, 1991)
Snow cover is an important variable for climate and hydrologic models due to its effects on surface albedo, energy, and moisture budgets. A model is currently being developed at the University of Colorado which will provide global snow cover information on a daily/operational basis. The basic data generated for each grid point (40 km resolution) are calculated average snow depth, maximum snow depth, age in days of the total snow cover, number of days since the last surface accumulation, as well as data source flags and summary diagnostics.Surface measurements used by the model are obtained through the World Meteorological Organization (WMO) synoptic data collection network. The model also uses passive microwave satellite data (DMSP/SSMI) which provide global, all-weather, day/night information on snow cover extent. In addition, the potential to extract snow depth information from passive microwave data is utilized.Special routines have been developed to handle problems associated with both surface observations (optimal interpolation, extrapolation into data-sparse mountain areas, missing data) and passive microwave
Keywords: Global snow cover, Global Snow Cover Model, Monitor

Snow sensor data quality indexing - Brandow, C.A.; Lourick, A. (59th Annual Western Snow Conference, 1991)
California's automatic snow sensing network produces volumes of snow water equivalent (SWEQ) data. Even when the data is reduced to daily values, the sensor network produces over ten-thousand SWEQ values per snow season. With such a large and rapidly growing record, identifying which sensors and periods have good quality data and which do not is a problem. One solution is to index the quality of the snow sensor data. This paper describes a snow data quality index (SDQI) system that has been devised for California's snow sensor network. Using a unique feature of the California Data Exchange Center (CDEC) data base, SDQI scores, indicating the relative quality of the data, can be calculated for each sensor by water year. An SDQI score of zero indcates no usable data. An SDQI score of one-hundred indicates perfect data---should we ever achieve such a thing. These SDQI scores can be computer generated, using a program we wrote for this purpose. The SDQI scores can be displayed in a table.
Keywords: Automated network, Automatic Snow Sensing, Sensor editing, Snow Data Quality Index

Effects of sampling density on estimations of snowpack characteristics - Cooley, K.R.; Rango, A. (59th Annual Western Snow Conference, 1991)
While remote sensing offers great potential for snowmelt modeling, many of the techniques being proposed need to be tested against ground truth (actual snow measurements), but how does one determine the number of measurements required? Unfortunately, the number may depend on the parameter being measured and on the variability of the snowpack. One of the problems in determining the density or intensity of measurements needed is the lack of validating information. In this study, samples obtained on a 30 by 30 meter grid over a 26 hectare wind swept basin in southwestern Idaho are used to determine the number of samples needed to adequately describe snowpack characteristics under conditions of extreme spatial and temporal variability. Estimates of snow covered area obtained from sample measurements are compared with estimates based on aerial photos. Estimates of snow water equivalent and snow depth are determined for a range of grid and sample spacings.
Keywords: Aerial photographs, Distribution, Sampling, Snow, Snowmelt, Variability

A scaled index of winter severity - Farnes, P.E. (59th Annual Western Snow Conference, 1991)
A procedure for indexing the severity of a winter would be helpful to wildlife managers and general public in understanding how mild or how severe conditions are for any given season or month. The Scaled Index of Winter Severity (SIWS), has a scale from -4.0 for most severe to +4.0 for mildest with 0 being near a normal winter. The index uses minimum daily temperatures, snow depth, snow water equivalent, snow density and precipitation accumulation (or SWE), above or below a threshold level. The weightings and threshold for each parameter can be changed to represent different species. Stations can be accumulated or weighted to represent winter range areas. Months can be looked at individually or accumulated for a season. Depending on the area, summer growth on winter ranges may also be a factor affecting winter severity.Frequency analysis of data provides probability of nonexceedance that is used to determine the level of any given component or combined components for the winter severity index.Trends of SIWS for a portion of Yellowstone National Park for the past 40 years is presented.
Keywords: Precipitation, Snow, Temperature, Wildlife, Winter severity, Yellowstone National Park

Bringing federal coordination to snow surveys: An historical survey - Helms, D.; Mergen, B. (59th Annual Western Snow Conference, 1991)
Drought in the 1930's prompted western interests to push for legislation to authorize federal coordination of snow surveys. Although small in number, the core of snow survey supervisors in the Bureau of Agricultural Engineering, and later in the Soil Conservation Service, created a regional network by eliciting cooperation from other federal and state agencies that managed land in the West and from conservation districts. The paper will discuss the history of important issues that have revolved around federal coordination of snow surveys. Some of those issues are the role of research in snow survey operations, development and adoption of new technologies such as oversnow vehicles and SNOTEL, organizational arrangements and location of snow survey operations in the Soil Conservation Service, and the expanded uses of snow survey information. Sources for the paper are records of the Bureau of Agricultural Engineering and the Soil Conservation Service in the National Archives, publications, and oral history interviews.
Keywords: History, Snow survey

A history of rain-on-snow floods in the Sierra Nevada - Kattelmann, R.C.; Berg, N.H.; McGurk, B.J. (59th Annual Western Snow Conference, 1991)
The largest floods on record in Sierra Nevada rivers have resulted from rainfall extending into the snowpack zone. Several large rain-on-snow floods have been documented in the 19th century that allow us to estimate that 16 regional floods exceeding the general magnitude of the largest floods of the past decade have occurred in the past two years. Although some of these events have been much larger than others in particular river basins, rain-on-snow floods with the potential to cause serious damage throughout the Sierra Nevada may recur, on the average, about once per decade. Floods with a ten year recurrence interval tend to be about twice as large as the mean annual flood in most Sierra Nevada rivers. There were no obvious trends in flood magnitude or frequency over the period of record.
Keywords: Flooding, Rain-on-snow, Snow-zone watersheds

Time series analysis of hydrometeorological data - Kite, G. (59th Annual Western Snow Conference, 1991)
Analyses of hydrometeorological time series for practical purposes, for example to aid in the design of reservoirs for hydroelectric power generation, have generally assumed stationarity of the data. Similarly, climatologists have related their analyses to 30-year climate `normals'. The most obvious exception to this general assumption has occured when the effects of man on a watershed are so large as to force attention; for example, the various diversions into and out of the Great Lakes.Recently, attention has concentrated on a much larger scale anthropogenic effect, the `greenhouse warming' and it's anticipated change in climate and, hence, in water resources. Projections have forecast decreases in runoff of up to 50% resulting from an increase of 1 degree C in temperature.
Keywords: Climate change, Hydrology, Lake levels, Time series analysis

Variation of snow water equivalent and streamflow in relation to the El Nino/southern oscillation - Koch, R.W.; Buzzard, C.F.; Johnson, D.M. (59th Annual Western Snow Conference, 1991)
Snow water equivalent (SWE), precipitation and seasonal streamflow for selected locations throughout the western United States were related to an index of the El niño/Southern Oscillation (ENSO). The strongest relations were observed when either the summer or fall averaged Southern Oscillation Index (SOI) was correlated with the maximum SWE, winter season precipitation and streamflow during the subsequent runoff season. These results suggest that the SOI can be used as a predictor of both SWE and streamflow as early as October each year with varying degrees of confidence. The magnitude of the correlations were quite variable throughout the western U.S. with the strongest associations observed in the Pacific Northwest. During El niño events, SWE, precipitation and streamflow tend to be below normal. When the opposite condition, often called La Nina, occurs SWE, precipitation and streamflow tend to be above average. These results have some important implication in water supply forecasting.
Keywords: El Nino, SOI, Water supply forecasting

Trends in snowcourse and streamflow data in British Columbia and the Yukon - Leith, R.M. (59th Annual Western Snow Conference, 1991)
In this study, records for nine snowcourse and eighteen streamflow stations in British Columbia and the Yukon are analyzed for trends which may be associated with climate change. The longest record is 72 years and the shortest is 26 years.Streamflow and snowcourse data have properties such as non-normal distribution, missing record and external interventions which impede statistical analysis. In particular, interventions (changes) may significantly affect the stochastic manner in which a series behaves. Such changes generate trends. For these reasons the analysis of such data is conducted using various smoothing techniques and test statistics, generally termed exploratory data analysis.From a visual examination of the output of the smoothing techniques, it appears that there is a tendency over the last thirty years for a decrease in snow water equivalent and streamflow in the southern portion of British Columbia and an increase in the north. But a more rigorous statistical analysis shows only a small percentage of the records have statistically significant trends.
Keywords: British Columbia, Snow course, Streamflow trends, Trends, Yukon

Climatology of snowfall-event characteristics at Denver - Mahoney, J.L. (59th Annual Western Snow Conference, 1991)
A climatology of snowfall-event characteristics for Denver, Colorado, was developed to help improve snow fall forecasts. A snowfall-event is a period of time during, which any type of frozen precipitation is observed at the station. A break between events occurs when 12 hours elapses with no precipitation. Hourly surface observations from 1948 to 1988 were examined for these features. In the investigation, characteristics such as diurnal oscillations in snowfall, preferred beginning/ending time of an event, and temperature and wind patterns were considered.The statistical approach used to analyze event characteristics reveals several interesting relationships. For example, the beginning time of precipitation is strongly tied to the timing of frontal passages, which are dependent on the time of day. One mechanism responsible for the diurnal periodicity in frontal passages is the temperature pattern. During the warmest part of the day in the spring and fall, cold fronts are insufficient in depth to penetrate west of the Continental Divide. At sunset, the temperature quickly cools so the front can continue its movement south.
Keywords: Climatology, Event forecasting, Snowfall event, Winter forecasting

North American participation in the WMO solid precipitation measurement intercomparison - Metcalfe, J.R.; Hanson, C.; Pangburn, T. (59th Annual Western Snow Conference, 1991)
In North America, standard methods of snowfall measurements vary significantly not only between the United States and Canada but within each country. In order to address hydrological and meteorological problems of concern to both countries, compatible spatial and temporal measurements of precipitation are required. The World Meteorological Organization (WMO) has initiated an international comparison to assess national methods of measuring solid precipitation to determine the wind related errors in measurement, including consideration of wetting and evaporative losses, and to derive standard methods for correcting solid precipitation measurements. The reference method in this 5-year intercomparison which began in 1987, is an octagonal vertical double-fence surrounding a Tretyakov precipitation gauge.
Keywords: Measurement, Precipitation, WMO

The western regional climate center - Redmond, K. (59th Annual Western Snow Conference, 1991)
The Western Regional Climate Center (WRCC), inaugurated in 1986 and located at the Desert Research Institute (a part of the University of Nevada System), is one of six which serve the contiguous United States. The area covered by WRCC consists of the eleven western states. Data are also available from Alaska and Hawaii. The center acts to fill several functions at the regional level: a) Maintain historical and current regional databases. These include those of NOAA and of other agencies. b) Disseminate and interpret original and manipulated data and information for users. c) Improve cooperation and coordination among governmental and private organizations of climate services at state, regional and national levels. d) Perform research on problems of applied climatology and meteorology.
Keywords: Climate data analysis, Climate databases, Regional Climate Centers

A trend of decreasing snowmelt runoff in northern California - Roos, M. (59th Annual Western Snow Conference, 1991)
During the last couple of decades, the fraction of annual natural runoff during the April through July period in California's Sacramento Basin has decreased. The decline seems to have started around 1960. Estimates of natural or unimpaired runoff are developed by adjusting measured flow for upstream water development. There is no evidence of changes in the way the estimates are derived. Although the trend is compatible with global warming, it is doubted that this is the reason. Some subtle shifts in patterns of precipitation appear to be the primary cause, along with some prominent midwinter rain floods which have increased the winter fraction of runoff. The trend may be part of some broad scale regional shifts in ocean or weather patterns.
Keywords: Climate change, Precipitation pattern shifts, Runoff patterns, Snowmelt runoff, Water resources

A comparison of snowmelt models for erosion prediction - Tarboton, D.G.; Al-Adhami, J.M.; Bowles, D.S. (59th Annual Western Snow Conference, 1991)
The prediction of erosion requires precise information on the rate of snowmelt delivery to the soil surface and drainage courses where erosion may occur. We have developed a modular approach to snowmelt modeling that can combine and interchange components from several popular energy balance and temperature index models such as the SHE model, PRMS model and USU model. Comparisons are made against data from SNOTEL sites widely distributed in the western U.S., as well as some experimental sites where more detailed data are available. These sites cover a range of settings with differing forest cover density, climatic region and elevation. We evaluate the various models and model combinations with a view to determining the most appropriate combination for use in an erosion prediction model.
Keywords: Erosion prediction, Process-oriented, Snowmelt model, WEPP

Climate and hydrological circumstances antecedent to selected landslide events in southeastern British Columbia - Toews, D.A. (59th Annual Western Snow Conference, 1991)
Debris torrents and debris avalanches in southeastern B.C. are usually associated with snowmelt. The hydroclimatic circumstances and possible influence of forest harvesting on 6 landslide cycles that occurred over a 10 year period are investigated in this paper. Slides appear to occur when a rain storm or a hot spell coincide with peak snowmelt at the particular elevation zone above an unstable slope. Melt may be due to either rain-on-snow or radiation and case studies of slides illustrating each circumstance are examined. The event that caused the largest amount of impact was a 90 mm rain-on-snow event on July 12, 13, and 14, 1983. This storm caused hundreds of debris torrents in watersheds with a significant area above 2000 m, the approximate snow line at the time of the slides. In 1988 at least 10 debris avalanches were associated with a radiation event in mid April, when the snow line was at a much lower elevation. Snowmelt data collected from a nearby lysimeter indicated peak snowmelt of 22 and 40 mm respectively in a forested and clearcut site.
Keywords: British Columbia, Mass washing

Seasonal snowpack dynamics and chemistry in the Sierra Nevada (California, USA) and the Tien Shan (Xinjiang Province, China) - Tonnessen, K. A.; Elder, K.J.; Kattelmann, R.C.; Williams, M.W. (59th Annual Western Snow Conference, 1991)
As part of NASA's Earth Observing System (EOS) Program we are investigating the hydrology and hydrochemistry of small, headwater basins that are seasonally snow-covered. Two of these study sites are the Emerald watershed on the western slope of the Sierra Nevada, Califonia (2800 m) and Dry Cirque, located at the headwaters of Urumqi River in the Tien Shan, northwestern china (3800 m).The objective of this research is to understand the physical and chemical dynamics of seasonally snow-covered regions of the earth in an effort to detect changes in global hydrologic and biogeochemical cycles. To realize this objective we are studying drainages ranging from 1 sq km to 100 sq km in area. Field surveys will be used in conjunction with remote-sensing data to predict and monitor the impact of climate change.
Keywords: China watershed, Season snow-covered basins, Snowpack chemistry, Snowpack dynamics

Global change: can we detect its effect on subalpine hydrographs - Troendle, C.A. (59th Annual Western Snow Conference, 1991)
The subalpine Water Balance Model (WATBAL) was used to simulate the effect of temperature and precipitation change on streamflow from subalpine forests. Comparisons are made between the simulated change and the long-term variability of observed flow. The magnitude of the simulted flows were well within the range of observed flow but the timing of the peak, under a warming scenario, was advanced 3-weeks.
Keywords: Global change, Simulated flows, Subalpine hydrology, Warming scenario

Effect of global warming on Sierra Nevada mountain snow storage - Tsuang, B.J.; Dracup, J.A. (59th Annual Western Snow Conference, 1991)
Snowmelt runoff processes in an alpine watershed located in the Sequoia National Forest are analyzed using an energy-based snowmelt runoff model. Using a global warming scenario, the results of the analysis indicate that the hydrograph of snowmelt runoff shifts between 19 and 93 days earlier and the snow season ends between 25 and 68 days earlier at an elevation of 2800 m. The most striking change is a decrease in the snow/precipitation ratio at elevations below 2300 m. Here the ecological balance suffers a major impact due to a small increase in air temperature that causes a significant amount of snow to occur as rain. In addition, the shorter snow season decreases the albedo of the land surface since the albedo of snow is much higher than that of vegetation or soil. As a consequence, regional warming is increased due to a snow albedo feedback process.
Keywords: Global change, Global warming, Sierra Nevada

Is April to July runoff really decreasing in the western United States - Wahl, K.L. (59th Annual Western Snow Conference, 1991)
Several investigators have presented evidence that the ratio of April-July runoff to annual runoff has been decreasing in Western North America. The trend has been recognized both in rainfall-runoff and snowmelt-runoff streams. The decline in this ratio has been attributed to a change in the seasonal distribution of precipitation; there is concern that the changing ratio reflects a decrease in April-July runoff. Analysis of streamflow records for gaging stations that record natural flow confirms that the ratio has been declining at selected streamflow stations along the Pacific coast. The decline in the ratio, however, is by no means pervasive. Furthermore, tests for monotonic trend, while confirming a decline in the ratio, show no discernable trend in total April-July runoff, indicating that April-July runoff has not decreased. The trend in the ratio does appear to represent an increase in winter precipitation.
Keywords: Annual runoff, Fractional runoff, Seasonal runoff, Trends

1990 Title, Contents, and Minutes (58th Annual Western Snow Conference, 1990)

Precipitation extremes at the Central Sierra Snow Laboratory, California - Azuma, D.L.; Berg, N.H. (58th Annual Western Snow Conference, 1990)
Information on return periods of precipitation in snow country is essential to a variey of engineering tasks--including estimating structural loading, designing reservoir capacity, and forecasting runoff. Using records from 1899 to 1988, extreme value theory was used to develop 10-, 20-, 50-, and 100-year return periods for precipitation during 1- to 10-day intervals at the Central Sierra Snow Laboratory in California's Sierra Nevada. Precipitation ranged from over 14 cm for the 10-year return period and 1-day interval to almost 70 cm for the 100-year return period and 10-day interval. During the 89-year daily precipitation record, mean daily precipitation was 11 cm but ranged up to 118.2 cm for individual days. Mean precipitation was 38-40 cm for many of the longer (12+ days) events and was over 78 cm for one 10-day event. Precipitation is common at this site with 1-, 2-, and 3-day precipitation periods occurring an average of 25 times annually.
Keywords: Central Sierra Snow Laboratory, Precipitation extremes, Sierra Nevada

Coping with extreme points of view - Brandow, C.A. (58th Annual Western Snow Conference, 1990)
Should snow sensors remain in wilderness areas? This controversial question has persisted since the Wilderness Act was passed by congress in 1964. In 1989, the Western Snow conference reaffirmed its position by publishing a brief policy statement. To gauge public sentiment, responses to this policy statement were solicited from a large number of individuals, groups, and officials. This paper summarizes the range of viewpoints on this question, and suggests how this information could help derive a political solution to this problem.
Keywords: Snow sensors, Wilderness

A method of modeling the frequency characteristics of daily snow amount, for stochastic simulation of rain-on-snowmelt events - Brunengo, M.J. (58th Annual Western Snow Conference, 1990)
In the mountainous West, rain-on-snowmelt (R/SM) storms are common events having extreme effects: warm winter rains combine with snowmelt to generate water inputs greater than either could produce alone, which can then result in flooding and lansdslides.A stochastic approach to estimation of R/SM properties uses a computer model to create a series of simulated storms, with the realizations examined for insight into the storms' effects. My study involves modeling of storms, and the resultant snowmelt and percolation, based on data from the Cascade Range of Washinton. I have adpated a mixed-probability distribution, with regression against date and elevation, to estimate the probable amount of snow on the ground when the storm occurs.These methods can be used to generate frequency curves, define the location of the transient snow zone, and compare the effects of R/SM events on cleared and forested land.
Keywords: Cascade Range, hydrometeorology, Rain-on-snowmelt, Stochastic modeling

Let's involve school kids in data collection efforts - Clagett, G. (58th Annual Western Snow Conference, 1990)
School teachers are extremely receptive to new ideas that provide a 'hands-on' learning experience for kids. Climate data, so vital to our everyday lives, is a natural for the science classroom environment. Kids are fascinated by the relationships of everchanging weather to the historical normals and extremes. The teachers like to use the current data collected in practical applications of local interest and as real-life projects to apply to computer training. In Alaska, schools throughout the state are collecting daily precipitation, snow depth, snow water content, and temperature data for the entire schoolyear for their own uses and submitting these data to the Soil Conservation Service for publication and entry into the Central Forecast System data base. The kids, with a little supervision, don't take a back seat to anybody when it comes to collecting consistent accurate data. Alaska's 'Schoolyards' climate data collection program has application to any rural school in the nation.
Keywords: Schools, Snow data collection

Changes in the timing and magnitude of high and low flows, 1958-1988, Eagle Creek, Oregon - Fedora, M.A. (58th Annual Western Snow Conference, 1990)
Eagle Creek is located on the south face of the Wallowa Mountains in northeastern Oregon and has a snow dominated runoff regime. A multiple regression approach was used to detect changes in streamflow extremes over a 31 year period. Measures of snow-water equivalent, temperature, precipitation and time were used as independent variables with peak flows and the timing and volume of streamflow available for irrigation as dependent variables. The magnitude of peak flows was best explained by the April 1 snow-water equivalent. Variation in the timing of low flows during the irrigation season was best explained by the April 1 snow-water equivalent and mean April-June temperature. The volume of streamflow through the irrigation season (July 1-September 30) was best explained by the April 1 snow-water equivalent, mean April-June temperature and time (in years). The time variable was significant at the 90% confidence level and indicated that streamflow available for irrigation increased by an average of 0.038 inches per year (316 acre-feet per year) over the study period.
Keywords: Oregon, Regression, Snowmelt

Learning from watching snowmelt - Frazier, J.W.; Brandow, C.A. (58th Annual Western Snow Conference, 1990)
The WRENSS handbook contains a hydrologic procedure for estimating increased water yield from silvicultural treatments. The difference in annual evapotranspiration for a forested watershed under harvested and unharvested conditions approximates the annual water yield increase. Annual water yield inreases predicted by WRENSS require area precipitation and general forest stand characteristics. However, forest stand characteristics had little effect on predicted water yields. Annual water yield estimates were only as accurate as the basin wide precipitation data. The WRENSS predicted water yield increases were accurate for the snow dominated region. Potential model upgrades include improved estimates of snow vaporization, evapotranspiration rates, indexed precipitation or orographic functions, and assessment of streamfow generation processes from alpine areas for water yield increases in alpine-subalpine basins.
Keywords: Bed load movement, Ice flow, Oversnow flow, Rain-on-snow, Snowmelt observations, Stream morphology, Subalpine meadows

Improvements in snow sensor installation techniques - Gehrke, F.; Hart, D. (58th Annual Western Snow Conference, 1990)
Much of the snow zone within the State of California lies at high elevation in remote areas. Increasing demands on the water supply forecasting activity has resulted in the need for accurate and timely mesurement of the current snowpack. Introduction of snow sensors to this environment has resulted in some unique obstacles to maintaining the measurement equipment. This poster paper presents solutions developed by the California Cooperative Snow Surveys program to two of these problems, bear damage to the sensor tanks and waterproof housing for the pressure transducer.
Keywords: Bears, Installation, Snow sensor

Temporal accumulation and ablation patterns of the seasonal snowpack in forests in varying stages of growth - Hardy, J.P.; Hansen-Bristow, K.J. (58th Annual Western Snow Conference, 1990)
The effects that varying forest structures, resulting from timber harvest, have on a snowpack's distribution, its snow water equivalence (SWE) and its ablation rate were examined in order to better understand the potential timing and volume of runoff within a forested watershed. Four plots of varying forest structure were measured for snow depth, snow density, and SWE throughout the snow accumulation and ablation season of 1988-89. Results indicate a good negative correlation existed between canopy density and maximum SWE accumulation (Pearson's coefficient = -.54; p-value = .0000). The pre-harvest water regime, in terms of snow accumulation and the rate of ablation, of a cleared forest may not return until the mean age of the forest approaches 79 years.
Keywords: Acid precipitation, Algae, Chemistry, Microorganisms

Status of the California cooperative snow survey program - Hart, D.; Gehrke, F. (58th Annual Western Snow Conference, 1990)
California occupies a unique position in the West of administering its own snow survey and water supply forecast program. This program, which was established in 1928 by the Legislature, is currently administered by the Department of Water Resources and combines the efforts of the Department and a number of other interested agencies throughout the State. This paper presents a history of the program and its approach to meeting the needs of the water users in California.
Keywords: California, Snow survey

Refinements in the remote sensing of snow-covered area - Holroyd III, E.; Carroll, T.R. (58th Annual Western Snow Conference, 1990)
Snow-covered area can be mapped in the visible bands by Landsat MSS, SPOT, and GOES systems. But the white snow is difficult to distinquish from white clouds and saline soils. Conifers and other vegetation can obscure the satellite view of a snowpack. There can also be discontinuous snow within a pixel for any of the available resolutions. Refinements in the operational techniques have been investigated. Adjusting image brightnesses to approximate vertical sun and flat terrain and then subtracting a summer reference image increases the detection of snow in mountainside conifers. Such change detection also seems appropriate for saline soils. Fractional snow coverage, as seen by Landsat, was compared with the brightness of snow in the coarse AVHRR pixels. Vegetative cover and snowpack aging make it inappropriate to adopt a simple transformation from snow brightness into percent snow-covered area with a pixel.
Keywords: AVHRR, GOES, Remote sensing, Snow cover mapping

Use of state-of-the-art systems for optimum water management - Horciza, E. (58th Annual Western Snow Conference, 1990)
Moist Pacific air masses and effects from the Pacific 'high' can create a wide range of weather conditions in California. As a result, the annual runoff in California has ranged from 18 to 167 million dekameters during recent years. Such variability of the water supply makes it difficult for water agencies and public utilities to manage optimally their water resources.Pacific Gas and Electric Company, which owns and operates fifteen hydroelectric developments in northern and central California, uses many state-of-the-art methods and equipment to make the best possible use of the available water supply.The systems PG&E uses to manage its water resources and to comply with license and contract requirements include supervisory control and data acquisition systems, dam, canal, and penstock safety monitoring systems, power plant efficiency monitoring systems, the Hydroelectric Systems Scheduling Model, and Hydro-Thermal Optimization Model.
Keywords: Equipment, Extremes, Systems, Water Management, Water supply

An evaluation of methods used by different river forecast centers to calculate reasonable maximum and reasonable minumum forecasts - Huber, A.L. (58th Annual Western Snow Conference, 1990)
This paper compares methods used by the different river forecast centers for calculating the reasonable maximum and reasonable minimum water supply forecasts. Five procedures used by different forecast centers were identified and evaluated. Results from using the five methods on common watersheds with the same prediction equations are summarized and compared for four forecast dates. Although each method purports to provide estimates of the reasonable maximum and reasonable minimum that would be exceeded only 10 percent of the time, or once every ten years, the actual return periods for the difference methods ranged from 3 years to over 500 years.
Keywords: Multiple regression, Reasonable maximum, Reasonable minimum, Statistics, Water supply forecasting

Snow fencing for water supplies - Jairell, R.L.; Schmidt, R.A. (58th Annual Western Snow Conference, 1990)
Drought conditions during 1988-89 in southeastern Wyoming created opportunities to test several snow fence designs that capture snow as a water source for livestock, wildlife, and fisheries. Snow fence-embankment combinations that were most efficient in small-scale tests proved to be good choices to provide livestock water at several locations where deep wells went dry. Removal of upwind brush and installation of a metal apron in the accumulation area improved efficiency of a snow fence that supplied a guzzler for wildlife. Another snow fence accumulated enough additional water to prevent winter kill in a fishery.
Keywords: Snow fence, Water supply

Future directions of snow surveys and water supply forecasting in the Soil Conservation Service - Johnson, D.E. (58th Annual Western Snow Conference, 1990)
This paper will cover five aspects of the future direction for Snow surveys and Water Supply Forecasting in the SCS:1. Increasing demands on water resources and needs for data,2. Data collection technologies,3. Water supply forecasting,4. Interagency cooperation, and5. Decision making for water resources.
Keywords: Data collection, Interagency cooperation, Water resources, Water supply forecasting

Snow hydrology of an alpine basin in the Sierra Nevada - R C Kattelmann (58th Annual Western Snow Conference, 1990)
Hydrologic and meteorologic observations at Emerald Lake in Sequoia National Park over a five-year period provide the first detailed description of the snow hydrology of an alpine basin in the Sierra Nevada. More than 95 percent of all precipitation was in the form of snow. Prolonged periods between storms permit sublimation losses to exceed 20 cm per winter, but little or no melt occurs during the winter in basins with northern exposure. Seasonal snow storage prior to spring melt ranged from 60 to 200 cm water equivalence. Average basin-wide snowmelt was about 1 to 1.5 cm per day in April and May and up to 3 cm per day in June and July. Peak snowmelt runoff exceeded 0.75 cm per day on at least 20 days per year. Instantaneous discharges rarely exceeded 0.5 cu m/sec/sq.km. More than 75 percent of the peak snowpack water equivalence and spring precipition became streamflow.
Keywords: Alpine hydrology, Sierra Nevada, Snow hydrology, Snowmelt

Freezing resistance of arctic tundra plants on Svalbard - Odasz, A.M. (58th Annual Western Snow Conference, 1990)
Arctic tundra plants collected from limestone-ridge vegetation on Svalbard (79 N) in summer survived freezing tests to only -2 degrees C or -4 degrees C. In winter, although injured by freezing, species retained capacity to grow after tests to -67 degrees C. Plants also survived -67 degrees C in a simulation experiment with 'continental' conditions where high ambient temperatures caused water stress while soils remained frozen. Most species survived the effects of a simulated warm spring followed by a freeze. Surprisingly there was no difference in cold tolerance of graminoid and cushion-plant herbaceous species.
Keywords: Arctic, Cold tolerance, Freezing resistance, Tundra

Possible climate change and its impact on snowmelt and water supply in California - Roos, M. (58th Annual Western Snow Conference, 1990)
Global Climate modelers are forecasting relatively large future climate changes, with warming of 2 to 5 degrees C. The changes, if they do come to pass, would have profound impacts on California's water resources. A shift in runoff patterns would be expected with less spring snowmelt and more winter runoff. This shift will make it difficult to fill major multi-purpose reservoirs once the flood season is past, with losses in water yield and hydroelectric power. Also the predicted rise in sea level may cause problems with water transfer in the Sacramento-San Joaquin Delta. Increased risk of levee failures in the Delta and a potential increase in ocean salinity intrusion could affect water supplies of the central and southern portions of California.
Keywords: Climate change, Global warming, Greenhouse effect, Sea level rise, Snowmelt runoff, Water projects, Water resources

Snow in mountain watersheds: Connections to climate and ecosystem health - Sommerfeld, R.A.; Fox, D.G.; Musselman, R.C. (58th Annual Western Snow Conference, 1990)
The amount of snow accumulated annually in mountain watersheds profoundly affects those watersheds as well as downstream users. The amount of snow affects the snow melt pattern and the delivery of water and associated nutrients to ecosystems. In turn, the amount of snow is affected by larger scale variables such as wind, precipitation and temperature. The chemistry of the snow pack is affected by atmospheric quality and affects productivity and health of dependent high elevation lakes and streams. Processes associated with these interactions are reviewed. A series of studies designed to improve our understanding of the role of mountain snow on regional water availability and on the health and viability of high-elevation ecosystems will be outlined.This paper also reviews snow research conducted at the Glacier Lakes Ecosystems Experiment Site (GLEES) in the Snowy Range Mountains.
Keywords: Climate, Ecosystem, Snowpack chemistry

The 1948 flood of the Columbia river an analysis of its cause and its importance in operation planning - Speers, D.D.; Barcellos, D.J.; Wortman, R.T. (58th Annual Western Snow Conference, 1990)
The 1948 flood on the Columbia River has significant implications to the Corps of Engineers in the formulation of flood control criteria for reservoirs in the Columbia basin, because it had a large runoff forecast error - in which spring runoff was significantly greater than predicted by snow and winter precipitation indices. An analysis was made of the hydrometeorology of this event, including the magnitude of the snowpack, magnitude and distribution of spring rainfall, and temperatures. Using the SSAARR hydrologic model these factors were simulated in various combinations and compared with other years. The conclusions were that no single factor that produced the flood was extremely rare, but their combination was relatively unique. The event could be considered more rare than its nominal recurrence interval of approximately 50 years computed from streamflow records.
Keywords: Floods, Reservoir Operations, Snowmelt modeling, Water supply forecasting

Using ratios of runoff to snow water content and to projected rainfall to-come, as a method of narrowing the water supply forecast range - Stein, R.E. (58th Annual Western Snow Conference, 1990)
The need to provide accurate, weekly water supply forecasts when snow surveys are conducted only monthly, and the need to be continuously prepared if dry conditions persisted during this last drought, led to development of a forecasting technique that uses a combination of snow survey information, and the historical relationship between runoff and snow water content and rainfall. The observed decrease in the historical ratio of runoff to precipitation as seasonal rainfall declined, was included in the forecasting technique.Initially, runoff amounts (water years) for all available years of record were compared with seasonal rainfall (rainfall years) to develop runoff to rainfall ratios, which provided the general change in the ratio from wet to dry years.
Keywords: Ratio, Water supply forecasting

Discharge characteristics of a rangeland stream - Sturges, D.L. (58th Annual Western Snow Conference, 1990)
Ice formation in the fall and early winter in combination with increasing distance from a spring affected short-term discharge characteristics of a small rangeland stream. Average daily flow measured 4.6 km downstream from the spring was reduced more than 25% on 55 days over a 21-year period. On another stream, discharge measured 45 m below the spring was stable because water remained above freezing. Intraday discharge rates were extremely erratic when icing was active; maximum daily discharge was commonly four or more times larger than minimum discharge. Such restrictions in flow probably have important biological impacts. Daily discharge data ensembles, transformed into modular coefficients, did not show a normal distribution.
Keywords: Discharge reduction, Icing effects, Rangeland, Stream, Streamflow

Estimating snow transport from wind speed records: estimates versus measurements at Prudhoe Bay, Alaska - Tabler, R.D.; Benson, C.S.; Santana, B.W.; Ganguly, P. (58th Annual Western Snow Conference, 1990)
A process-based model for wind-transported snow developed by Pomeroy (1988) has been used to derive an equation relating total snow transport in the first 5 m above the surface, q(sub0-5) (kg/m.s), to 10-m wind speed, u(sub10) m/s:q(sub0-5)=u(sub10)exp4.04/458800This equation is valid for u(sub10) >or= 6.5 m/s when snow supply is unlimited. A four-year comparison at Prudhoe Bay showed that snow transport estimated by this relationship compared favorably with measured snow accumulation at tall snow fences when basic requirements for snow conditions and wind data were satisfied. Analysis of historical wind records at Prudhoe Bay for 1968-1989 provided estimates for snow transport.
Keywords: Blowing snow, Snow fences, Snow transport, Snowdrifts, Wind speed

Comparison of two methods for remote measurement of snow depth - Tanner, B.D.; Gaza, B. (58th Annual Western Snow Conference, 1990)
Hourly snow depth and snowpack temperatures were measured in the Wasatch Mountains of northern Utah over the winter of 1988-89. Measurements were retrieved remotely via a radio frequency link. A commercial acoustic sensor originally developed by Atmospheric Environment Service, Canada (Goodison, et al., 1988) was used for the snow depth measurements. A thermocouple (TC) string constructed to minimize heat transfer along the TC wires was used to measure temperatures in a profile at 10 cm spacings.The acoustic sensor performed well but disagreement with manual readings was often greater than the manufacturer's rated accuracy of +/-1 cm. New low density snow was sometimes underestimated. Snow depths estimated from the maximum daily temperature difference observed at a given height were generally within 1-2 TC spacings. The effects of heat conducted from the air to the TC junctions is evident in the measurements of the upper portion of the pack.
Keywords: Acoustic snow sensor, Snow depth, Snow measurements, Snow temperature

Hydrologic and biologic consequences of an avalanche striking an ice-covered lake - Williams, M.W.; Clow, D.W. (58th Annual Western Snow Conference, 1990)
The hydrological and biological effects of large avalanches striking ice-covered lakes have rarely been documented, due to the extreme weather conditions, remote locations and hazards often associated with these events. Here we report the effects of a large avalanche striking ice-covered Emerald Lake on February 17, 1986. The lake is located at an elevation of 2800 meters, in the southern Sierra Nevada, California. The avalanche, traveling about 20 m/sec, struck the lake with a force of 2.12x10(6) N. About 70% of the unfrozen water (90,000) m(3) in the lake was displaced into the outlet stream. The floodwave in the lake's outflow removed 5.4x10(5) kg of snow from the channel. Scouring of the streambed was observed throughout the exposed reach. The survival rate of embryos and sac fry from the resident brook trout (Salvelinus fortinalis), in the lake's outlet, decreased from close to 90% before the flood to 2.5% after the flood.
Keywords: Avalanche, Flood, Lake, Snow, Trout

1989 Title, Contents, and Minutes (57th Annual Western Snow Conference, 1989)

Correlation of average basin snow line estimates derived from SNOTEL, aircraft, and satellite snow cover data - Allen, M.W.; Palmer, P.L. (57th Annual Western Snow Conference, 1989)
For many years, water supply forecasters in the Western United States have employed various methods of estimating the average snow line elevation in mountainous watersheds. The US Army Corps of Engineers uses fixed-wing aircraft to estimate average snow line elevations for reservoir requlation. The US Soil Conservation Service operates a mountain snowpack telemetry system in the West (SNOTEL) for water supply forecasting. Since 1985, the National Weather Service (NWS) has been producing operational areal extent of snow cover data derived from satellite data for major basins in the West. In 1987, the NWS generated area/elevation curves for 275 Western basins using a digital elevation model. The area/elevation curves provide a common base for comparison of snow cover estimates by converting percent snow covered area to average snow line elevation. SNOTEL, airborne, and satellite snow cover estimates are (etc).
Keywords: Aircraft snow cover mapping, Area/elevation curves, SNOTEL data, Snow covered area

Detection of avalanches using atmospheric infrasound - Bedard, A.J. Jr. (57th Annual Western Snow Conference, 1989)
Long-range detection of avalanches may be feasible by detecting low-frequency acoustic waves generated by avalanche processes. A review of recent measurements of long-range atmospheric infrasound associated with avalanche activity indicates that unique acoustic signatures are launched by avalanches, perhaps providing a means of characterizing avalanche details at distances of hundreds of kilometers. This paper will review progress to date and indicate the form that an infrasonic avalanche detection system could take. The potential uses of a reliable detection system include avalanche forecast verification, comparisons with prediction models, and better definition of regional avalanche statistics.
Keywords: Acoustic waves, Atmospheric infrasound, Avalanches

A practical test of a telemetered accoustic snow depth sensor - Bergman, J.A. (57th Annual Western Snow Conference, 1989)
During the 1987-88 winter, data from an accoustic snow depth sensor and observed snow depth were compared at the Central Sierra Snow Laboratory in the Sierra Nevada of California. The Sierra snowpack is characterized as being deep and wet with melt occurring during mid-winter. Snow depth during the test period reached 190 cm and surface snow densities ranged from 110 kg/cubic meter to 400 kg/cubic meter. Surface melt-freeze crusts reached a thickness of 40 cm. Correlation between sensor telemetry data and observed 8 am snow depth was 0.99 with a standard error of estimate of 3.6 cm. On an hourly basis, snow depth from the accoustic sensor varied inversely (with) changes in air temperature during periods of no precipitation. Snow depth variations of up to 12 cm occurred between hourly readings and went as high as 17 cm over a 24 hour period. During the test period, air temperature ranged from -18 to 17 degrees centigrade with differences as high as 19 degrees centigrade between the maximum and minimum. The variations associated with temperature change were not (etc).
Keywords: Acoustic sensor, Snow depth, Snowpack, Sound

A sequential flash for photographing trajectories of saltating particles - Bird, K.G.; Jairell, R.L. (57th Annual Western Snow Conference, 1989)
To obtain statistically useful samples of the maximum heights attained by saltating snow during drifting, several thousand particle trajectories must be measured. This paper describes the light source for photographs of sufficient quality that computer analysis can determine heights automatically. The method uses eight small electronic flash units fired in sequence through color filters, with the light focused through a single lens. Since the number. color and interval between flashes can be varied, the device could be used for other studies where object position or speed is of interest.
Keywords: Electronic flash, Photographs, Saltating snow, Sequential time intervals

A good solution to the wilderness snow sensor problem - Brandow, C.A. (57th Annual Western Snow Conference, 1989)
There is a good solution to the problem of retaining some snow sensors in wilderness. However, it will require: 1) legislative action by Congress, 2) a major investment in improving forecasting techniques and hydrometeorologic networks, and 3) a small amount of give and take on the part of the parties involved in the debate. First, Congress needs to make the language in Title III, Section 305 of the Utah Wilderness act of 1984 applicable to the Wilderness Act of 1964 and all subsequent wilderness acts: 'the Wilderness act (1964) shall not be construed to prevent the installation and maintenacce of hydrologic, meteorologic, climatological, or telecommunications facilities, or any combination of the foregoing, or limited motorized access to such facilities when non-motorized access means not reasonably available or when time is of the essence, subject to such conditions as the Secretary of Agriculture and Secretary of the Interior deem desirable, where such facilities of access are essential to flood warning, flood control or reservoir (etc).
Keywords: Congress, Hydrometeorologic data, Sensor removal, Wilderness, Wilderness Act

Cost-benefit analysis of airborne gamma radiation snow water equivalent data used in snowmelt forecasting - Carroll, T.R. (57th Annual Western Snow Conference, 1989)
The paper briefly discusses (1) the technique used to make airborne snow water equivalent measurements using natural terrestrial gamma radiation, (2) the errors associated with airborne measurements made over agricultural areas, and (3) and estimate of the marginal and total costs to conduct the February 1985 airborne snow survey over Indiana, Michigan and Ohio.
Keywords: Airborne measurements, Gamma radiation, Snow survey, Total costs

Assessing the effects of climate changes on snowpack and streamflow - Cooley, K.R. (57th Annual Western Snow Conference, 1989)
Projected increases in the atmospheric concentration of carbon dioxide could significantly change the earth's climate. Estimates of expected changes in temperature and precipitaion have been made by a number of researchers using theoretical models, empirical relationships, and actual long-term climatic data. The estimated changes range from warming the global surface temperatures by more than 4 degrees celsius, to cooling the surface temperature somewhat, and increasing or decreasing precipitation by about 10% in certain areas or regions of the world. In this sudy, the National Weather Service River Forecast System Model (NWSRFS) was used to estimate the effects of temperature and precipitation changes, of the magnitude suggested, on snowpack and streamflow for the Lower Willow creek Watershed, Montana, which is a predominately snowmelt-fed system.
Keywords: Climate change, Runoff, Snowmelt

A direction toward improved streamflow forecasting in the western mountains - Day, G.N.; Schaake, J.C.; Ellis, J.H. (57th Annual Western Snow Conference, 1989)
Conceptual hydrologic modes can be used to simulate basin snowpack and resulting streamflow. These models account for the detailed water balance of a basin and require accurate estimates of mean basin precipitation and temperature. The high spatial variability of precipitation in the mountains and the relatively sparse network of point measurements can lead to large uncertainties in modeling precipitation and current snowpack conditions. Improved estimates of snowpack conditions and their uncertainties will translate into more reliable streamflow forecasts. Other data, i.e., point and flight line water equivalent, areal extent of snow cover, and streamflow represent additional sources of important information that might be used to adjust model simulated conditions. This paper presents a framework for incorporating these data and an orographic precipitation model into a forecast system. It also presents a (etc).
Keywords: Conceptual models, Forecasting, Snow, Water Supply

Interannual variations in snowpack in the Rocky Mountains - Doesken, N.J.; Chanano, D.; McKee, T.B. (57th Annual Western Snow Conference, 1989)
Unpredictable year to year variations in surface water supplies present substantial challenges to present and potential water managers and users in the West. As a part of a study of climate variations and their effect on Western water supplies, data from USDA Soil Conservation Service snowcourses with continuous data since at least 1951 have been investigated for the entire area from the southern Rockies to the Canadian border. Several characteristics of snowpack variations have been indentified and will be described. Systematic differences in snowpack distribution between wet and dry years will be discussed. Large-scale associations between snowpack, gage precipitation and streamflow will be presented. Reasons for year to year regional flucuations in the ratios of snowpack to precipitation and snowpack to streamflow will be suggested. Finally, apparent long-term trends toward wetter winters in the southern Rockies and drier winters farther north will be assessed in terms of known climatic flucuations.
Keywords: Climate variability, Hydrologic variability, Snowpack, Streamflow

Estimating the effects of wildfires on water supply in the northern Rocky Mountains - Farnes, P.E.; Hartman, R.K. (57th Annual Western Snow Conference, 1989)
Wildfires during the summer of 1988 burned a significant portion of several Northern Rocky Mountain wastersheds. A procedure was needed to adjust pre-burn calibrated water supply forecasting procedures to reflect post-burn conditions. The described procedure operates with a set of physically based, empirical relationships derived from data collected in Western Montana and Northwestern Wyoming. The premise of the procedure is that a reduction in timber canopy will lead to reduced interception of snowfall and spring precipitation. It is proposed that reduce summer evapotranspiration will have a minor effect on the concurrent seasonal volume. Instead, reduced summer evapotranspiration will have its greatest effect on the following season's volume by providing a higher level of antecedent soil moisture.
Keywords: Water supply forecasting, Wildfire

Snow microorganisms and their interaction with the environment - Hoham, R.W. (57th Annual Western Snow Conference, 1989)
Snow microorganisms include bacteria, algae, fungi, lichen pieces, protozoa and rotifers. The dominant forms are algal flagellates, Chloromonas and Chlamydomonas (Division Chlorophyta). Snow algae have been reported from 13 western states in mountainous regions, high elevation plateaus and high latitudes. The distribution and coloration of individual species is most regulated by irridation levels, and thus snowfields containinf algae may be red, yellow to orange, or green. Several species have been studied axenically in the laboratory, and results indicate that nutrients, pH, temperature, light and allelopathic effects from conifers may influence their growth. Studies indicate that snow algae accumulate trace metals in high concentrations. Acid precipitation may be selecting for more acidic strains of snow algae in the NE U.S. when compared to strains studied from Arizona snow. Preliminary studies in New York and Quebec indicate that snow algae appear to affect snow chemistry through metabolic processes.
Keywords: Acid precipitation, Algae, Chemistry, Microorganisms

Mapping snow cover with satellite imagery: comparison of results from three sensor systems - Holroyd, E.W. III; Verdin, J.P. (57th Annual Western Snow Conference, 1989)
A satellite snow cover mapping project was jointly undertaken by the NWS, USGS, and the Bureau of Reclamation. It included an intercomparison of results obtained from three statellite sensor systems: GOES-VISSR, NOAA-AVHRR, AND Landsat-TM. The study area was the San Juan Mountains of southwest Colorado during the 1987 melting season. snow maps were operationally produced for 5 dates from GEOS visible (1+ km) data using successive images to remove clouds. snow maps for 8 dates derived from NOAA-AVHRR (1 km) data used a partitioning of albedo versus elevation. A second method partitioned spectral space defined by AHVRR Band 1 (visible) and the combination of band 3 minus band 4 (both IR) to lessen the thermal component of band 3. A similar partitioning of spectral space of Landsat-TM band 3 (red) and band 5 (mid-IR) defined snow.
Keywords: GOESS-VISSR, Landsat-TM, NOAA-AVHRR, Snow cover mapping

Water release from a low elevation snowpack in the Sierra Nevada - Kattelmann, R.C.; McGurk, B.J. (57th Annual Western Snow Conference, 1989)
The intermittent snowpack zone of the Sierra Nevada occupies more than a third of most river basins on the west slope of the range. Snow cover changes rapidly throughout winter in this one from about 1000 m to 1600 m elevation. Despite the importance of this region in producing winter streamflow, little is known about its snow hydrology. Measurements from three snow melt lysimeters of 20 square meters each at Blue Canyon provide the first detailed look at snowpack water release in the imtermittent snow zone of the Sierra Nevada. At this site, water input to the soil occurs almost continuously over a six month period. Snowmelt occurs on almost all winter days except during snow storms. New snow begins to melt within a few hours after a stom. The shallow snow cover causes little delay to rainfall and can melt rapidly during particularly warm storms. Combined rainfall and snowmelt at the site has exceeded 20 cm per (etc).
Keywords: Intermittent snowpack, Snowmelt, Water release

A hydrologic model using remotely sensed data - Kite, G.W. (57th Annual Western Snow Conference, 1989)
The paper describes the application, on a microcomputer, of a distributed hydrologic model, with snow component, using data from satellite as well as conventional ground-based data. The data are combined in a database written as a 'front-end' for hydrometeorological modelling on micro-computers. Two basins in western Canada with significant snowpack are being studied; the Kootenay and the Souris. The model has seven components and is modular form so that components can be quickly changed. Daily visible and near infra-red data from a NOAA satelite are used, both from digital tape and from black and white photographs. The objectives of the study are to investigate the utility of data from satellite in a hydrometeorological model in different physiographic and climatic areas, and to use the model as a test bed for different physically-based components.
Keywords: Hydrology, Modelling, Remote sensing, Satellite

Reservoir operations guides - application on three reservoirs - Marron, J.K.; Farnes, P.E.; Pacheco, C. (57th Annual Western Snow Conference, 1989)
The Soil Conservation Service, Water Supply Forecasting Staff developed and released a technique and software to help water users manage reservoirs to achieve the goal of the structure whether that goal was to optimize water supply for irrigation or reduce damage done by excess runoff. the reservoir management technique reviewed here bases nanagement decisions on water supply forecasts. The technique has been applied on several reservoirs in the west. Three reservoirs were selected for review. All of these reservoirs are dominated by snowmelt runoff. This paper will review the possible implications of the application of this process.
Keywords: Management technique, Operation Goal, Reservoir Operations, Water Supply Forecasts

Evolution of a research-oriented snowmelt-runoff simulation model into an operational forecasting tool - Rango, A. (57th Annual Western Snow Conference, 1989)
Although many snowmelt-runoff models are proposed, only a few make it to the stage of true operational application in the forecast mode.There are many pitfalls and barriers that must be overcome to successfully transform a research model into an operational product. Such evolution is a gradual process with many aspects to consider. Some important considerations are model complexity, user compatible software, operational requirements, availablitity of required input data, forcasts of meteorological data, simulation and forecast reliability, applicability in geographically diverse areas, and realtime updating capabilities. Experiences with the snowmelt-runoff model (SRM), which requires remote-sensing inputs, are used as examples of the evolutionary process. The current status on SRM will be examined, and specific forecasting situations will be illustrated on the Upper Rio Grande basin of Colorado.
Keywords: Model development, Remote sensing, Snow cover, User compatibility

Required accuracy of input data for WRENSS to determine silvicultural treatment effects on annual water yield - Stednick, J.D. (57th Annual Western Snow Conference, 1989)
The WRENSS handbook contains a hydrologic procedure for estimating increased water yield from silvicultural treatments. The difference in annual evapotranspiration for a forested watershed under harvested and unharvested conditions approximates the annual water yield increase. Annual water yield increases predicted by WRENSS require area precipitation and general forest stand characteristics. However, forest stand characteristics had little effect on predicted water yields. Annual water yield estimates were only as accurate as the basin wide precipaitation data. The WRENSS predicted water yield increases were accurate for the snow dominated region. Potential model upgrades include improved estimates of snow vaporization, evapotranspiration rates, indexed precipitation or orographic functions, and assessment of streamflow generation processes from alpine areas for water yield increases in alpine-subalpine basins.
Keywords: Modelling, Silvacultural treatments, Water Yield

Automated collection of water-quality and discharge data on streams - Sturges, D.L.; Winter, C.J. (57th Annual Western Snow Conference, 1989)
The availability of relatively inexpensive electronic sensors for measuring water quality parameters and the availability of data loggers with low power requirements enable water-related data to be collected from remote sites at a reasonable cost. We present information about a system installed on a stream that collects information about water conductivity, pH, temperature, water stage, and air temperature. Information about sensor installation and calibration procedures, system maintenance tips, and samples of several data output formats are also presented.
Keywords: Automatic collection, Data loggers, Hydrologic investigations, Water stage

Evaporation and seepage from a livestock reservoir equipped with a snow fence for water recharge - Sturges, D.L. (57th Annual Western Snow Conference, 1989)
Drifting snow can provide water to recharge livestock reservoirs on windswept lands that normally receive little surface inflow. Field experience with such installations indicates that snow fences collect significant quantities of snow, but that the stored water is often gone by the grazing season. A study was conducted in the spring of 1988 to determine the quantity of water lost by evaporation and by seepage from a small livestock reservoir recharged from snow deposited by a snow fence. Measurements started during snowmelt and extended through June when the pond was nearly dry. Evaporation was sensitive to daily wind movement and ranged to 1.3 cm per day. Pond seepage, however, exceeded evaporation several fold. The factor limiting success of the snow management effort was leakage from the reservoir.
Keywords: Blowing snow, Livestock reservoirs, Snow drift, Snow fences

Snow management increases alfalfa yields - Waddington, J.; Steppuhn, H. (57th Annual Western Snow Conference, 1989)
Three varieties of alfalfa were seeded in May of 1986 into random plots within and adjacent to a 3.3 ha (8 acre) shelterbelt consisting of Orbit tall wheatgrass wind barriers located near Swift Current, Saskatchewan. The barriers had been established from a 1976 double-row, north-south oriented seeding spaced 15 m apart and now occupying about 5.5% of the land area. The grass annually produces culms which over the years averaged 1 m in height and provided a snow-deposition zone whose annual maximum capacity exceeds the 75th snowfall percentile by 3 fold. Although this maximum was not reached during any season since the alfalfa was seeded, snow cover retentions at the time of measurement in 1987 and 1988 averaged 150% or greater than those surveyed outside the shelterbelt. Alfalfa forage production on 60 plots, half within and half outside the shelterbelt, was measured during the 1987 and 1988 growing seasnons; no comparisons were made in the 1986 establishment year. Oven-dried, above-ground biomass in (etc).
Keywords: Alfalfa, Shelterbelts, Snow deposition, Tall wheatgrass windbreaks

Statistical forecast model for Libby basin, Montana - Wortman, R.T. (57th Annual Western Snow Conference, 1989)
A statistical procedure has been developed that significantly improves the inflow volume forecast for the basin above Libby Dam, Montana. The criteria used to assess the forecast performance is the standard error of the first-of-month forecast of the April-August runoff volume. The previous model fitted a multivariate linear regression model to the observed April-August runoff using lumped values derived from observed snow, rain, and antecedent runoff variables. During the forecast season station averages were used as surrogates for unavailable variables. The factors in the new procedure instrumental in reducing the standard errors were 1) restructuring from a single-season regression equation for two subbasins to a single basin best-fit model developed for each date-of-forecast, 2) employment of a 'best correlation to residuals' scheme to aid in variable selection, and 3) use of principal components regression to develop the final model, presented in terms (etc).
Keywords: Best-fit model, Principal components, Standard error, Volume Forecast

1988 Title, Contents, and Minutes (56th Annual Western Snow Conference, 1988)

Toward correlating California's wilderness snow sensors - Brandow, C.A.; Azuma, D.L. (56th Annual Western Snow Conference, 1988)
Following a strict interpretation of the Wilderness act (P.L. 88-577), the US Forest Service (USFS) insisted and the California Department of Water Resources (DWR) agreed to correlate the wilderness snow sensors with sensors outside USFS-administered wilderness. Further, SWR agreed to install these 19 wilderness snow sensors by 1989, and to remove them by 2004. This paper outlines the progress that has been made on this correlation effort. Topics reviewed are: 1) background of the USFS/DWR agreement and subsequent events, 2) installation and operational status of the wilderness and correlative snow sensors, 3) techniques for editing snow sensor data, 4) efforts to develop and test a suitable statistical methodology for performing the correlations, and 5) an attempt to estimate the effects of removing the wilderness snow sensors on water supply forecasting, assuming succssful correlations. Finally, the authors speculate on the future of the correlation effort and possible alternatives.
Keywords: Hydrometeorology, Snow sensors, Water management, Wilderness

The Wyoming windshield - an evaluation after 12 years of use in Alaska - Clagett, G. (56th Annual Western Snow Conference, 1988)
Wyoming windshields in Alaska indicate a catch efficiency on the order of 80 to 90 percent of total snowfall rather than only 48 percent, as reported by the U.S. Forest Service's Rocky Mountain Forest and Range Experiment Station (Sturges 1948). Also, Wyoming windshields afford a catch 200 percent greater than National Weather Service's standard unshielded gages during the November to April coldest period of the winter and 100 percent greater for the whole winter. These assertions are based on a fairly small collection of comparable data. But the implication remains firm that the Wyoming windshield provides the best available estimate of snowfall in windy, exposed and remote locations.
Keywords: Arctic, Precipitation, Snow Surveys, Wyoming Windshield

Snowpack variability on western rangelands - Cooley, Keith (56th Annual Western Snow Conference, 1988)
Snow accumulations vary greatly on large tracts of western rangelands due to wind patterns, topography, and storm characteristics. These variations complicate water supply and flood forecasting techniques. Most hydrologic models assume snow accumulation and melt to be unifom over relatively large areas or elevation zones. Detailed measurements of snow depth and density, precipitation, snowmelt, and streamflow on a 26 hectare watershed in southwestern Idaho were used to assess the magnitude of the variations and to assist in understanding the processes involved. Samples taken 30 meters apart varied in depth from zero to 5 meters, and snow density determined from the same samples varied from less than 15 to over 50. The relationship between accumulated snow and accumulated precipitation was different for each field and exposure. Streamflow responded to overland flow from early snowmelt and subsurface flow from later melt of isolated drifts.
Keywords: Runoff, Snow Density, Snow depth, Snowmelt, Streamflow

The Canadian automatic snow depth sensor: a performance update - Goodison, B.E.; Metcalf, R.A.; Wilson, R.A.; Jones, K. (56th Annual Western Snow Conference, 1988)
In Canada, a need exists for a reliable, low cost automatic snow depth sensor. The Atmospheric Environment Service (AES) has developed and tested an acoustic ranging device, which provides an accurate and economical method of measureing snow depth remotely. The AES sensor has been licensed for commercial manufacture. Field tests were conducted at various sites across Canada, to assess the accuracy and performance of the sensor. Results indicated that the automatic sensor measured within plus-or-minus 2.5 cm of independent ruler measurements, and over the winter season, its measurement time series replicated daily ruler measurements. The sensor is now configured to measure with a 1.00 mm resolution; however, it is not practical to expect measurement accuracies of this precision over such a dynamic surface as snow. Factors which can influence the measurements of snow depth and snowfall using acoustic ranging devies are presented. With proper siting, the AES Automatic Snow Depth Sensor provides a reasonable and accurate measurement of snow depth.
Keywords: Acoustic, Automatic sensor, Commercial, Ranging, Snow depth

Precipitation measured by gages protected by the Wyoming shield and the dual-gage system - Hanson, C.L. (56th Annual Western Snow Conference, 1988)
The Wyoming shield and dual-gage measuring systems were developed to measure all precipitation, but more specifically, snowfall under windy conditions. Results of studies that were designed to determine precipitation catch relationships between the two systems for climatic conditions on the Reynolds Creek Experimental Watershed in southwest Idaho are reported. The computed catch from a tree-protected dual-gage system was 2 to 3% more than from a nearby unprotected dual-gage system mesasured the same amount as Wyoming shielded gages when air temperatures were higher than -2.2 degrees C. For snowfall, amounts computed form the dual-gage system were slightly more, especially under windy conditions.
Keywords: Catch efficiency, Dual-gage system, Precipitation gage, Wyoming shield

Portable animal protection shelter and wind screen - Jairell, R.L.; Schmidt, R.A. (56th Annual Western Snow Conference, 1988)
Shelters formed by locking two steel corral panels in a 'V' pointing into the wind and covering them with reinforced plastic tarp or plastic snowfence provide temporary protection from wind and drifting snow. Developed primarily to aid stockmen by protecting problem animals during calving, these portable shelters also facilitate machinery repair or construction outdoors during blizzards or strong winds. Tests comparing porous (snowfence) and solid (tarp) coverings show greater wind protection with the porous cover, which also collects a snowdrift if blowing snow occurs. The solid tarp causes greater turbulence in the protected region, giving less wind protection, but no snow deposition occurred in tests during blizzards. Panels used in the tests were 5 ft high, 8 ft long, and weighed 105 lbs. Shelters were stable in gusts to 60 mph, when pointed into the wind. Anchoring is recommended if wind reversal is a possibility.
Keywords: Animal shelters, Blizzards, Snow drifts, Wind protection

Snow volume comparisons for atmospheric deposition monitoring - Marks, D.; McGurk, B.J.; Berg, N.H. (56th Annual Western Snow Conference, 1988)
Chemical loading due to atmospheric deposition depends on both snowfall volume and chemistry. At a forest clearing in the central Sierra and at a windy site in the southern Sierra Nevada, precipitation, air temperature, wind direction and speed, and humidity were recorded. At the sheltered site, precipitation volumes from replicated shielded and unshielded Belfort gauges were similar. The experimental collector's volumes were similar to the Belfort's volumes. At the windy site, the daily and weekly snow boards collected more snow than the experimental or Belfort collectors. At the forest site, the inability of the snow boards to retain rain and melt caused their seasonal totals to be less than the other devices. The traditional 'wet-dry' precipitation collector worked well at the sheltered site, but only with frequent servicing by technicians. This 1-year study showed that uniform procedures will not produce accurate volume and chemical concentration data at sites with different physical characteristics.
Keywords: Atmospheric deposition, Precipitation gauges, Snow boards, Snow measurement, Snow pits

Flow fingers and ice columns in a cold snow cover - Marsh, P. (56th Annual Western Snow Conference, 1988)
When melt water infiltrates into a dry snow cover, the wetting front does not move uniformly into the snow. Instead, it breaks up into well defined flow fingers. These flow fingers are there since they allow water to move rapidly into the snow-pack without wetting the entire snow cover. As a result, melt water may reach the snow-pack base well before the entire pack is wet and isothermal at 0 degrees C. An understanding of these processes is essential in order to predict melt water run-off. These flow fingers are very difficult to study under normal situations. They are often short lived, they are not easy to see visually in a snow pit, and they are not easily studied with remote instrumentation. However, if the snow is sufficiently cold, enough water will freeze to block all the snow pores, with ice columns the final result. Because these features are easy to locate, they provide an exellent method to study the natural movement of water into the dry snowcover. Field work carried out in the Mackenzie Delta, N.W.T., in 1986 and 1987 provided excellent observations of the formation of ice columns. This work has important implications to snow metamorphism processes in both warm and cold snow covers, and therefore to the modeling of snow-melt runoff.
Keywords: Snow melt, Snow metamorphism, Water flux in snow

Density of new snow in the central Sierra Nevada - McGurk, B.J.; Azuma, D.L.; Kattelmann, R.C. (56th Annual Western Snow Conference, 1988)
The density of newly fallen snow is often assumed to be 100 kg/cu m (10%) so that water equivalent can be estimated from snow depth. Unlike snow in the Rocky Mountains, Sierran snow often falls at near-freezing temperatures, and warmer temperatures could result in snow with a higher density. Three years of replicated snow board measurements were analyzed to determine the effects of air temperature on new snow density. Analysis of 282 replicates showed that, for boards within 5 m of each other, the mean difference was 1.3 kg/cu m. For the 4 years, 403 samples produced a mean new snow density of 120 kg/cu m with a 95 percent confidence interval of 4.8 kg/cu m. The average air temperature was -3.1 degrees C with a standard deviation of 2.6 degrees C, but numerous storms had above-freezing average temperatures. While plots of temperature versus density showed a positive correlation, regression of temperature on density produced a standard error of 38 kg/cu m and a coefficient of determination of only 0.27.
Keywords: Air temperature, Snow, Snow board, Snow density, Snow density prediction

Snowpack-vegetation dynamics: mountain hemlocks in the Lake Tahoe area - Nachlinger, J.L.; Berg, N.H. (56th Annual Western Snow Conference, 1988)
Snow patterns within mountain hemlock (Tsuga mertensiana) stands were compared to those within other adjacent subalpine vegetation types in the Lake Tahoe area. We found that more snow accumulated in mountain hemlock stands than in shrub stands. Snow cover lasted longer in the mountain hemlock stands than within the other vegetation types. Avalanche activity, elevation, slope inclination, and site moisture all snow related parameters were important in determining stand size structure. Snow, site moisture, and parent rock material were important factors in determining species composition in hemlock forests. Mountain hemlock stands with relatively moderate snow accumulation potential had the greatest species richness.
Keywords: Mountain hemlock, Snow accumulation, Snow duration, Species composition, Stand size structure, Subalpine vegetation, Tsuga mertensiana

Use of new SSAR model automatic adjustment updating procedure - Orwig, C.E.; Davis, E.M. (56th Annual Western Snow Conference, 1988)
Real-time forecast operations with the SSARR model have always required that the model have a routine to automatically adjust model streamflows to abserved conditions. Recently, efforts by the Corps of Engineers and the National Weather Service have led to an improved method for automatic model adjustment. Testing of the new procedure on both a rainfall runoff area and on a snowmelt area demosntrate that the new method shows promise for application in real-time forecasting efforts.
Keywords: Real-time Forecasting, Snowmelt modeling

The SCS snow survey water supply forecasting program: urrent operations and future directions - Palmer, P.L. (56th Annual Western Snow Conference, 1988)
The Soil Conservation Service (SCS) operates a Snow Survey and Water Supply Forecasting program in the Western United States, to provide information on forthcoming water supplies from streams that derive most of their runoff from snow melt. A network of over 1800 manual snow courses and 500 automated SNOTEL sites is used in predicting spring and summer streamflow volumes at over 500 forecast points west-wide. An automated data analysis and product dissemination system, known as CFS (Centralized Forecast System), analyzes and archives snow and other hydrometeorologic data, generates stramflow forecasts and related products, and disseminates these products to water users and managers in a timely manner.
Keywords: Centralized Forecasting System (CFS), SNOTEL, Snow surveys, Streamflow Forecasting, Waster Supply Forecasting

Seasonal streamflow forecasting in the Upper Rio Grande basin by incorporating the use of SNOTEL data in the SSAR hydrologic model - Perkins, T.R. (56th Annual Western Snow Conference, 1988)
The SCS has calibrated a conceptual hydrologic computer model (SSARR) for the Rio Grande near Del Norte, Colorado, to determine if improvements to seasonal runoff estimates can be made. Since the model can be calibrated using data from a short time series, SNOTEL data from sites located in the high producing areas of the basin were used. Also, watershed relationships, such as soil moisture conditions, can be conceptually integrated to help reduce the forecast variability.
Keywords: Rio Grande, SNOTEL, SSARR, Streamflow runoff model

Results of 1986 snow acidity sampling in California - Roos, M. (56th Annual Western Snow Conference, 1988)
During 1986, snow surveyors in the California Cooperative Snow Surveys Programs field tested the snowpack for acidity while doing their regular snowpack depth and water content measurements. The purpose of the special sampling was to provide broad coverage of the snow zone in California to see if there appeared to be a widespread problem of snow acidity or if specific 'hot spots' or zones of acidity existed. The field tests of surface snow acidity were made with small litmus paper test kits. About 520 snow course determinations of pH were made from about January 1 through April 1. Field pH values clustered around 5.3, not significantly different from the 5.6 theoretically expected from clean precipitation. Results did not indicate any widespread acidity problem in the California snowpack, at least not in 1986.
Keywords: Acid rain, Acid snow, pH, Snowpack chemistry

A peakflow forecast for Payette Lake using SNOTEL data - Sarantitis, B.C.; Palmer, P.L. (56th Annual Western Snow Conference, 1988)
Flow into Payette Lake, Idaho has been regulated within natural range since at least 1923. The goal is to capture the maximum volume of runoff without causing high water damage to the lakeshore. Flow restriction is by tainter gates and removable stoplogs, a method which allows only a minimal flow adjustment once the stoplogs are placed. If outflow is stopped too far ahead of peak flow, the risk for high water around the lakeshore increases; if peak flow is missed, the maximum runoff volume may not be captured. A large proportion of runoff to Payette Lake is contributed by the late lying, high elevation snowpack in the surrounding mountains. The snow water equivalent in the pack is available on a daily basis from Soil Conservation Service SNOTEL sites in the basin. Climatic data is recorded at several NWS CLIMATE stations in the basin and daily runoff flows are generated by the Bureau of Reclamation using lake levels. This is combined to forecast the date of peak runoff and a volume flow and provides an operational tool for efficient reservoir regulation.
Keywords: Peak flow, Reservoir management, SNOTEL, Snowmelt runoff, Streamflow

Measuring snow interception and loss from an artificial conifer - Schmidt, R.A.; Jairell, R.L.; Pomeroy, J.W. (56th Annual Western Snow Conference, 1988)
A 1-m high artificial christmas tree and the snow held on its branches is weighed by an electronic balance that transfers values to a computer in a nearby mobile laboratory. An insulated box provides a stable environment for the balance, and plastic bushings in a metal tripod gave low-friction support to the vertical shaft supporting the tree. Measurements are sufficiently accurate that evaporation of intercepted snow could be correlated with environmental factors during periods as short as 10-15 min, for mid-winter conditions in a lodgepole pine stand.
Keywords: Snow, Snow evaporation, Snow interception

The effect of in situ evaporation on perceived snow distribution in partially clear-cut forests - Swanson, R.H. (56th Annual Western Snow Conference, 1988)
Differences in snow found under trees and within clearings of partially clear-cut forests are variously attributed to interception, redistribution and/or aerodynamic trapping of the falling snow. Measurements in Alberta during 1973 revealed that the snow present on the tree- or clearing-side of the sunlit edges of 60 to 120 m diameter circular clearings was less than at the shaded edge, raising a fourth possibility; that of differential evaporation or melting of snow between the sunlit and shaded portions of clearings. The evaporation from snow during precipitation-free days in January through March 1985 was 0.18 mm d-1 under the trees on the shaded edge; 0.42 mm d-1 under trees on the sunlit edge. The 4 to 7 mm of evaporation estimated during the 22 snow-free days in February 1973, was less than 1/3 the 25 mm of precipitation that occurred. On March 1, the snow measured on treed and open sides of the north edge was less than the amount measured there on February 1. More than 18 mm of snow loss were unaccounted for by in situ evaporation from the snowpack.
Keywords: Clear-cutting effects, Evaporation from snow, Snow measurements

Estimating dates of the snow accumulation season - Tabler, R.D. (56th Annual Western Snow Conference, 1988)
It is often necessary to estimate the average snow accumulation season, defined as extending from the first persistent snowfall to the time of peak water-equivalent, as a first step in estimating average winter precipitation. The snow accumulation season is shown to be delimited by dates when air temperatures reach 0 degrees C, as computed from mean monthly temperatures. For locations lacking climatological records, estimates can be derived from multiple regressions relating 0 degrees C dates at surrounding stations to elevation, latitude, and longitude. Regression equations are presented for all states in the snow belt, and a general equation indicates that dates of the snow accumulation season vary at the average rate of 2.5 days per 100 meters of altitude, 5.5 days per degree of latitude, and 1 day per degree of longitude, earlier northward, eastward, and upward in the fall, and the reverse in the spring.
Keywords: Air temperatures, Precipitation, Snow accumulation, Snow transport

Numerical simulation of snow transport deposition, and redistribution - Tesche, T.W. (56th Annual Western Snow Conference, 1988)
The Snow Accumulation and Numerical Transport Algorithms (SANTA) model consists of a Mountain Windfield Model (MWM), a sophisticated Transport and Diffusion Model (TDM), and a bulk Cloud Microphysics Model (CMM). The model is formulated to treat atmospheric transport, cloud microphysics, snow deposition and resuspension at comparable levels of sophistication. In its general formulation, SANTA is a three-dimensional, time-dependent, multispecies hydrometeorological model. It simulates the time evolution of solid, liquid, and vapor water fields within fields within cold orographic storms over complex mountain topography, and may be applied for both local scale and regional scale analyses. Comparison of hourly and daily average snow accumulation and water equivalent precipitation predictions for the 30 March 1982 Sierra storm shows that the SANTA model predictions of total daily precipitation match observations closely. Based on preliminary verification exercises, the SANTA Model has potential as a tool in regional and local avalanche hazard forcasting.
Keywords: Snow deposition, Snow redistribution, Snow transport

Translating snow hydrology research results into guidelines for forest managers: gaps between theory and practice - Toews, D.A.A.; Gluns, D.R. (56th Annual Western Snow Conference, 1988)
The snow hydrology-forest harvesting interface is examined from the perspective of forest land managers who must make decisions on timber harvesting in watersheds used for community water supply. Particular reference is made to the problems encountered and the land management context in southeastern B.C. The background knowledge, guidelines, and analysis methodologies currently in use are briefly summarized. The gaps between theory and application are examined by addressing questions related to the topics of peak flows, water yield, and low flows that have arisen during discussions with land managers.
Keywords: Forest harvestiang, Forest land management, Snow hydrology

Snow deposition processes in a forest stand with a clearing - Troendle, C.A.; Schmidt, R.A.; Martinez, M.H. (56th Annual Western Snow Conference, 1988)
Electronic sensors supported on towers simultaneously measured the influx of snow falling into a forest and a clearing, in experiments to compare fluxes during storms with those occurring when wind redistributed intercepted snow after snowfall ceased. The latter process was intermittent and showed very low fluxes compared to those during storms.
Keywords: Snow, Snow interception, Snow redistribution, Wind

Hydrograph recession limbs - a case of deja vu - Van Haveren, B.P. (56th Annual Western Snow Conference, 1988)
The upper Columbia River Basin is snowmelt-dominated and characterized by a relatively dry precipitation regime in summer and early fall. Streamflows in the Basin peak in May or June, followed by a very constant recession decay from July to October. A method was developed to forecast monthly river flows during the latter part of the recession period. This method takes advantage of the uniformity in recession-period decay and the hydrologic momentum of large watersheds. A model-year approach is used where the target year's monthly flows are compared to the same recession period of all the years in the historical record. The period of record is searched for the model year which best matches, based on an appropriate objective function, the target year's hydrograph. Using regression analysis, a relationship is developed between the model year and the target year and then employed to predict future monthly flows in the latter portion of the recession period. Nearly every snowmelt hydrograph in the historical record has at least one other snowmelt hydrograph that very closely resembles it. This 'hydrograph similitude' can be used as a forecasting tool.
Keywords: Hydrograph similitude, Recession flows, Streamflow forecasting

Predicting snow course snow water equilavent - Zuzel, J.F. (56th Annual Western Snow Conference, 1988)
A procedure for predicting future snow course snow water equivalent from current data and the statistical characteristics of monthly historical data is presented. The method depends on the autocorrelation of snow water equivalent between months and includes a prediction error term which is determined for exceedance probability level of 10 through 90 percent. The algorithm was developed and tested using 44 years of January through April snow course data from a site in the Cascade Mountains of Oregon. Testing of the procedure produced acceptable results for high, average, and low years and for all exceedance levels. Results can be used to modify streamflow forecasts based on the probabilities of additional snow accumulation.
Keywords: Autoregression, Forecasting, Probability, Statistics

1987 Title, Contents, and Minutes (55th Annual Western Snow Conference, 1987)

Settlement pressures on roof structures - Albrecht, R.G. (55th Annual Western Snow Conference, 1987)
Buildings which are located in very heavy snow zones and which could be completely covered with snow during the winter have effective snow roof loads considerably in excess of the actual snow loads on the projected area of the roof. When this happens some weight of snow which would ordinarily be supported by the ground can be transferred through shear to the roof. Although no known experiments have been performed to evaluate the settlement pressures on an actual roof, data from shear and tensile tests on snow gives a means of estimating the weight of snow from the area surrounding a building which would be additive to the weight of snow directly over the roof. An experimental setup is proposed for measuring the increase in snow load due to settlement pressures on a buried roof. Buildings which have been known to have been damaged by settlement pressures are identified.
Keywords: Roof loads, Snow loads

The role of micro-computers in data acquisition and analysis at the Salt River project - Anderson, R.K.; Ester, C.E. (55th Annual Western Snow Conference, 1987)
The Salt River Project (SRP), a water and power utility serving the greater Phoenix area, operates a system of six water storage reservoirs on the Salt and Verde Rivers of central Arizona. Excess water cannot be released until the reservoirs are near their combined capacity of 2,000,000 acre flood events in the Phoenix area. Furthermore, updated hyrometeorology studies for the 13,000 square mile watershed indicate that reservoir capacities and dam outlet works are inadequate for controlling large flood flows. These concerns, coupled with recent improvements in watershed monitoring and forecasting, have led to the need for advances in data axquisition, processing and analysis system.
Keywords: Data Acquisition, Hydrometeorology, Microcomputers, Water Management

Accuracy and repeatability of in situ snow wetness measurements using the newly developed twin-disc capacitance sensor - Bergman, J.A. (55th Annual Western Snow Conference, 1987)
If water from snowmelt and rain-on-snow can be tracked as it moves through the snowpack, streamflow forecasters could be informed of the potential for excessive snowpack outflow before actual outflow occurred and gain time to apply mitigation procedures to accommodate the extra water. During the winter of 1985-1986, eight twin-disc capacitance sensors, used to track changes in the liquid water content of snow (wetness) at the USDA Forest Service’s Central Sierra Snow Laboratory, in northern California, were calibrated and tested for their ability to repeat measurements. For all sensors, snow volume wetness varied less than 0.06%, indicating low 'between measurement' variability. To assess accuracy, twin-disc sensor wetness was compared with wetness measured by the Denoth-Fogler snow moisture meter. For all sensors, the difference between the measurement means of the two methods was 0.25% snow volume wetness.
Keywords: Accuracy, Capacitance, Measuring undisturbed snow, Snow wetness, Twin-disc sensor

Assessing landslide occurrence with snow data and other site information - Cheng, J.D. (55th Annual Western Snow Conference, 1987)
In early April, 1985, large landslides occurred at several low elevation forested locations iN south central B.C. causing damage to railroad and fish habitats with economic and legal implications. The causes of these landslides were assessed using snow and temperature data as well as other site information. Field inspections revealed that several features combined to make these locations very susceptible to mass wasting. These features include steep and convergent slope, shallow soil with high density subsoil, and the evidence of scars from uprooted trees by previous windthrow. However, these landslides were considered to have been mainly triggered by an extraordinary climatic event that provided an extremely large amount of water to the soil. Analyses of snow course, snow pillow and temperature data indicate that this climatic event in fact produced record-breaking snowmelt water (380 mm) at these low elevation locations.
Keywords: Extreme Climatic Event, Landslides, Mass Wasting

Heavy snow failures - Coen, C.C.; Crane, D.A. (55th Annual Western Snow Conference, 1987)
A pictorial representation of various heavy snow failures. The paper includes various structural types: wood, post-tensioned concrete, and steel. It describes the failure of the Blyth Ice-skating Arena, site of the 1960 Olympics, and many other structures. Wood failures include compression perpendicular, horizontal shear, and bending. Also included are impact failures, ice dam failures, and others.
Keywords: Roof loading, Snow loads

Diurnal fluctuations in remote precipitation gage readings - Cooley, K.R.; Robertson, D.C.; Lute, D.; Beard, G.A. (55th Annual Western Snow Conference, 1987)
Precipitation gage readings from hundreds of remote sites could dramatically improve the accuracy of western streamflow forecasts. Unfortunately, diurnal fluctuations of more that 3 cm have been observed when precipitation did not occur. Reliable data must be available for forecasts to be accurate, since errors of 3 cm could indicate catastrophic flooding. This study attempted to determine the cause of the diurnal fluctuations. A simulated remote precipitation gage site was installed so that temperature and pressure readings could be monitored at 15-minute intervals, and visual observations and changes to the system could be made frequently. Results indicated that: (1) thermal expansion and contraction produced daily pressure changes of less than 0.3 cm of H20; (2) concentration of methyl alcohol-ethylene glycol affects the magnitude of the fluctuations; and (3) diurnal fluctuations (etc.).
Keywords: Flood Forecasts, Rainfall Measurements, Water Supply

The contribution of SNOTEL precipitation measurements to climate analysis, monitoring and research in Colorado - Doesken, N.J.; Schaefer, G.L. (55th Annual Western Snow Conference, 1987)
Precipitation data collected by the Soil Conservation Service SNOTEL network in Colorado is compared to traditional National Weather Service data sources for the 1980-1986 period. Differences in gages and observational procedures are shown to have significant effects on precipitation measurements. Differences in gages and observational procedures are shown to have significant effects on precipitation measurements. Improved gage catch efficiencies make SNOTEL measurements surerior to NWS data for the October-May winter season. Summer SNOTEL accueulation undermeasures precipitation by at least 10%. NWS data are superior to SNOTEL data for assessing timing and frequency of daily events, but SNOTEL data are adequate to show relative differences in precipitation frequencies from one location to another.
Keywords: Climate, Precipitation, Raingage, SNOTEL, Snowfall

Graphics system for SNOTEL data - Grimsted, L.A. (55th Annual Western Snow Conference, 1987)
Since the SNOTEL system acquires daily readings instead of the average six winter season readings, the increased volume of data was very difficult to handle using existing techniques. SNOTEL data analysis routines needed to be modernized to manage the large quantities of SNOTEL data. To address this need, SCS decided to develop a micro-comuter graphics software package for the data manager's use. This package provides the user with the ability to download the data from SNOTEL, file the data, edit, graphically display the data, and upload the edits to SNOTEL. This paper discusses the development of this graphics package including a description of the functions, the problems encountered during development, and the uses being made of this package.
Keywords: Editing, Graphics, Microcomputers, SNOTEL

Scaling and constructing models for outdoor snowdrift tests - Jairell, R.L. (55th Annual Western Snow Conference, 1987)
Reduced-scale models have proved a useful tool in predicting snowdrift patterns formed by structures and terrain features, solving practical engineering problems on an individual case basis. Successful modeling requires attention to dynamic conditions and to the model's proper scaling, their durability, and advanced preparation for modeling runs. This paper describes experience gained in 7 years of constructing these small-scale models that give consistant results in this dynamic environment.
Keywords: Blowing snow, Scale models, Snowdrifts

Methods of estimating liquid water storage in snowpacks - Kattelmann, R. (55th Annual Western Snow Conference, 1987)
Most streamflow forecasting procedures account for liquid water storage in the snowpack. More than a dozen methods of estimating this quantity have been developed. This paper evaluates and compares these known techniques both in terms of theory and application. The paper also compares estimates of snowpack water retention obtained from these various methods to change-in-density measurements, snowmelt lysimeter lag times, and response of small streams in the Donner Summit area of California. Measurements at the Central Sierra Snow Laboratory indicated that layers of fresh snow usually retained less than five percent liquid water by volume under conditions experienced over three winters. The response of snowmelt lysimeters to rain-on-deep-snow events indicated there are only a few hours of delay between the onset of rain and snowpack outflow. Similarly, small streams began to rise within a few hours of the beginning of rainfall.
Keywords: Liquid water, Snowmelt lysimeter, Snowpack water retention

A microcomputer-based watershed modeling and data-management system - Leavesley, G.H.; Lumb, A.M.; Saindon, L.G. (55th Annual Western Snow Conference, 1987)
The U.S. Geological Survey's Precipitation-Runoff Modeling System (PRMS), an interactive processor for hydrologic modeling and data management called ANNIE, and a modified version of the National Weather Service's Extended Streamflow Prediction (ESP) program have been modified and enhanced for microcomputer application. Watershed-simultion capabilities are provided by PRMS, a modular-design distributed-parameter watershed model. Model input is read from files prepared by ANNIE, and model output can be generated for graphical and statistical analysis by ANNIE. ANNIE helps a user interactively create, check, uptdate, reformat, transform, and statistically and graphically analyze meteorologic and hydrologic data. Forecasting capability is provided by the coupling of PRMS and ESP. ESP prodcuces a probablistic forecast for streamflow variables, such as maximum flow, flow volume, and the date flow decreases below a selected volume.
Keywords: Microcomputers, PRMS, Snowmelt Model

Factors limiting snowmelt runoff in a permafrost environment - Marsh, P. (55th Annual Western Snow Conference, 1987)
Snowmelt runoff has long been recognized as a major component of streamflow in permafrost environments. Due to the cold snow cover and soil in these regions, a number of processes combine to both delay and limit runoff from snow cover. In more temperate climates these processes are often ignored, but in northern areas they take on added importance and must be considered when calculating runoff. These processes include: reducing the cold deficit of the snow, soil heat flux, refreezing of soil infiltration, and the growth of basal ice. A field study of these processes was carried out in a lake basin in the Mackenzie Delta, N.W.T. During the 1986 snowmelt period, the cold content of the snow and the strong negative soil heat flux delayed the arrival of meltwater at the snow cover base, and most of the melt water infiltrated the soil. As a result there is little immediate runoff from snow cover to the lake. This has important implications to the hydrology of these Delta lakes.
Keywords: Melt Metamorphisis, Permafrost, Snowmelt Runoff

Roof snow loads; drifting against a higher wall - O'Routke, M.; Hmadi, K.E. (55th Annual Western Snow Conference, 1987)
Snow drifts at the change in elevation of a multilevel roof are considered. An analysis of actual field measurements indicates that the height of the triangular drift is related to the length of the upper level roof, suggesting that triangular drifts form at backward facing steps. Conversely quadrilateral drift heights appear to be related to the length of the lower level roof, suggesting that quadrilateral drifts form at forward facing steps. Among large drifts, the triangular shape is the most common. A previous empirical relationship for the drift height of triangular shapes is reviewed and a new empirical relationship for predicting quadrilateral drift height is presented. For the vast majority of quadrilateral shapes in the database, the measured ground load and drift were less than the design ground load and drift height specified in the 1982 American National Standard Institute provisions.
Keywords: Drifts, Roofs, Snow, Structural design

Observations on the consistency and reliability of field data in snow survey measurements - Powell, D. (55th Annual Western Snow Conference, 1987)
Since the first decade of the 20th Century, snow surveys have been taken manually with some version of the Mt. Rose snow sampler. Although increasingly augmented or superseded by more sophisticated and modern techniques, much knowledge of an valuable insights into what is involved in acquiring consistent and reliable data in a dynamic environment can result from long experience with field measurements and winter travel to and from data sites. The author has spent 30 years in measuring snow courses at high elevations in the southern Sierra Nevada, as well as field seasons in Afghanistan and Chile establishing snow survey programs. From this experience, he offers observations on problems, difficulties, and constraints in data acquisition which can be of value to users and interpreters of snow course data whatever method of acquisition is used in North America or elsewhere.
Keywords: Field measurements, History, Snow courses, Snow surveys

Snowmelt-runoff modeling in the microcomputer environment - Rango, A.; Roberts, R. (55th Annual Western Snow Conference, 1987)
The snowmelt-runoff model (SRM) is a simple degree-day model that requires remote sensing input in the form of basin of zonal snow cover extent. The model has been successfully tested on several U.S. and foreign basins in the simulation and forecast modes. In all these tests the model has been run on a mainframe computer. As operational application of SRM increases, it is assumed that the availability of a microcomputer version will allow easy widespread application plus minimize the turnaround time needed for operational forecasts. To facilitate its use, a SRM version has been developed for IBM compatible personal computers likely to be available in field offices. The program itself features user oriented input and multiple self help screens which allow the user to select the kind of data input used and the output products desired. The SRM microcomputer version has been tested successfully on several basins.
Keywords: Microcomputer, SRM Model, Streamflow forecast

Designing structures for snow loads - Sack, R.L. (55th Annual Western Snow Conference, 1987)
Economical structural design in deep-snow country requires an accurate prediction of ground and roof snow loads. The latest standard of the American National Standards Institute (ANSI) has focused attention on this area over the past 10 years. ANSI produced a new country-wide ground snow load map, Canada has been updating their national map, and many Western U.S. States have prescribed their local ground snow loads. The data bases used are those produced for runoff and weather predictions (i.e., SCS and NWS, respectively in the U.S.). Ground-to-roof conversion factors and data for additional considerations (e.g., ice damming, drifting, and lateral pressure) stem from studies sponsored by NRC of Canada, CRREL, NSF, and various local jurisdictions. The latest design information is being incorporated into the large building codes in the U.S. (i.e., UBC; and BOCA). Work is in progress to increase the knowledge data base, and incorporate these findings into the standards.
Keywords: Building Codes, Roof Loading, Snow Loads

Roof load predictions using artificial snow - Sack, R.L.; Giever, P.M. (55th Annual Western Snow Conference, 1987)
A series of companion field and laboratory studies have shown that roof snow loads can be efficiently and effectively modeled in a cold room. Water and air are precooled by a heat exchange unit before passing through mixing nozzles in a cold room where the temperature is controlled to meet the requirements of the experiment. The artificial snow has small crystals with specific gravity from 0.13 to 0.26. Small-scale gable and shed roofs, equipped with load cells and thermocouples, are placed in the cold room, and snow is deposited until the required depth is reached. The room temperature is regulated to yield the design weather pattern. Loads and temperatures are monitored periodically by a data logger and the information is transmitted to a central computer. Probabilistic models were developed and simulation used to predict 50-year mri roof loads. These loads were comparable to those predicted by a field-derived model.
Keywords: Artificial snow, Roof loads, Small scale modelling, Snow loads

Reliability of results and conclusions based on statistical analysis of hydrological data in land-use hydrology - Salway, A.A. (55th Annual Western Snow Conference, 1987)
Forest managers require answers to basic hydrological questions for operational planning of timber harvesting activities in consumptive use watersheds in the Nelson Forest Region of British Columbia. Considerable documented evidence indicates that forest cover removal results in increased snow accumulation in cutblocks and causes water yield increases in streamflow but the magnitude of such effects is highly variable. A selection of relevant case studies are examined, statistical tests applied to original data and conclusions drawn. Peak snow water equivalent increases in clearcuts relative to the forest are generally substantial but best described by linear regression equations, rather than average percentages that are highly variable. Annual and monthly streamflow increases have been obtained via paired watershed experiments but some decreases have also been observed.
Keywords: Case studies, Consumptive use watersheds, Increased snow accumulation, Statistical tests, Timber Harvesting

Slide rule for snow fence design - Tabler, R.D. (55th Annual Western Snow Conference, 1987)
A method for determining required height and number of rows of snow fences has been used for more than 10 years to design effective snow fence systems for controlling drifts and augmenting water supplies. Because the procedure involves complex equations that are difficult for the typical user to solve, a simple pocket-sized slide rule has been developed that allows required fence height to be quickly determined from input values for fetch (contributing distance) and precipitation. Other design criteria included on the slide rule include required spacing of fences from the area to be protected, snow storage capacity, and required number of rows of 4.5- and 9-ft fences. The paper explains the basis for all calculations and simplifying assumptions, and includes drawings of the scales needed to fabricate the slide rule.
Keywords: Blowing snow, Snow fences, Snow transport, Snowdrifts

Snow loads on multi-level flat roofs in Canada - Taylor, D.A. (55th Annual Western Snow Conference, 1987)
Between 1967 and 1982, snow depths and densities were recorded on 44 single- and multi-level flat-roofed buildings between Halifax and Edmonton. Analysis of the data indicates that the specific gravity of snow on roofs is about 0.3 and is on the average, about 18% higher than that recommended for design In the 1985 National Building Code of Canada (NBC). The paper presents maximum average and maximum roof snow loads on upper and lower roofs (outside the drifts) and compares these to values recommended for design in the NBC. Data on maximum snow loads in the drifts is compared to NBC provisions. The statistical variability of the snow loads is analyzed to aid establishment of load factors for Limit States Design in the Canadian Code.
Keywords: Building codes, Flat roofs, Multi-level roofs, Snow density, Snow drifts, Snow loads, Snow variability

Runoff in the Upper Colorado river basin, water years 1983-85, and comparisons with forecasts of runoff to Lake Powell - Wahl, K.L.; Collins, D.L.; Aldridge, B.N. (55th Annual Western Snow Conference, 1987)
Runoff in the Upper Colorado River Basin was unusually great during water years 1983-85. Measured runoff to Lake Powell during 1984 was only 0.3 percent less than the record measured runoff in 1917. The runoff for 1983 ranks third, and the 1985 runoff ranks seventh largest since 1914. The combined 2-year runoff for 1983-84 was a record. Recurrence intervals for peak discharges were generally less than 100 years, while recurrence intervals for volumes of 30 days or more exceeded 100 years at several gages in 1983 and at numerous gages in 1984. The virgin flow equaled that for 1917 and tied for second and third largest since 1895. Errors in the 1983 forecasts of runoff to Lake Powell were records, but the 1984 and 1985 forecasts were more accurate.
Keywords: Errors, Forecasting, Recurrence interval, Runoff, Upper Colorado River Basin

Interceptioon and redistribution of snow in a subalpine forest on a storm-by-storm basis - Wheeler, K. (55th Annual Western Snow Conference, 1987)
Small clearcut openings in subalpine forests commonly have 30% greater snow water equivalence (SWE) than the surrounding forest. This may result from the clearings capturing wind transported snow. This study measured the SWE in a small clearcut and the surrounding forest on a storm-by-storm basis. The average windspeed and SWE for each storm were compared to determine the effect of wind on snow accumulation. Redistribution of intercepted snow between storms occurred once out of the 21 possible times. It accounted for 2% of the measured accumulation in the clearing. Regression of the percent difference in SWE between the upwind forest and the clearing versus windspeed showed a negative correlation (r = -0.74). Acculumation in the clearing decreased relative to the forrest as the average windspeed increased.
Keywords: Clearcuts, Interception, Redistribution

1986 Title, Contents, and Minutes (54th Annual Western Snow Conference, 1986)

Snow accumulation patterns in the Sierra Nevada - Aguado, E. (54th Annual Western Snow Conference, 1986)
This paper examines the spatial characteristics of snow accumulations in the Sierra Nevada. In particular, it addresses the question of whether snow courses located within individual basins, but at differing elevations, are more consistent in having above or below normal accumulations than are locations of similar topography but greater spatial separation. Nearly thirty years of data for Feb. 1 and April 1 were obtained for 28 snow courses. The data were standardized and subjected to principal complonents analysis to obtain preliminary results regarding the homogeneity of the snow accumulation across the Sierra. Most stations were highly correlated with each other and loaded strongly on the first component. However, several sites at lower elevations exhibited less uniformity with the other snow courses. This results from the influence of warm weather precipitation being in the form of rain instead of snow at the lower elevations. More detailed examination of accumulation patterns will also be presented.
Keywords: Principal Components, Sierra Nevada, Snow Accumulation Patterns

Monitoring snowpack conditions with an interactive geostationary satellite system - Allen, M.W.; Mosher, F.R. (54th Annual Western Snow Conference, 1986)
The National Severe Storms Forecast Center (NSSFC) collects and maintains real-time data bases of atmospheric and surface observations in addition to full resolution GOES data with the Centralized Storm Information System (CSIS). These data sets and the analyses derived from these data sets are then combined with topographic, hydrologic and/or geopolitical boundaries to assist hydrologic users as well as the primary severe storm forecasting users. During the 1985 smowmelt season the Satellite Field Services Station (SFSS) began utilizing CSIS capabilities to derive operational digital snowcover maps from 1 km visible GOES data. These maps were derived for 85 United States Geological Survey (USGS) hydrologic catalog units covering 35,000 square kilometers. Optional 1986 services utilizing satellite data include snowcover mapping by elevation zones, solar insoH-tion, and skin temperature over snow covered area. Atmospheric observations of air temperature, relative humidity, wind speed and direction at 5,000, 10,000 and 18,000 feet can be combined with analyzed lapse rates to estimate free atmospheric conditions at specified elevations.
Keywords: Centralized Storm Information System, Interactive processing, Satellite hydrology, Snowcover mapping

A watershed management pilot project in Alberta - Bernier, P.Y.; Swanson, R.H. (54th Annual Western Snow Conference, 1986)
The Province of Alberta is currently planning a pilot-scale test of water yield increase through patch clear-cutting of timber. The chosen basin occupies 157sq km of foothills terrain. Planned operations call for 50% of the 98 sq km of operable forest to be harvested. Ideally, because of effect of wind on snow, clear-cuts should be kept small, with windward lengths between 5 and 8 times the height of the surrounding trees (H). The economics of timber harvesting disfavor small openings. The compromise reached between snow management theory and timber harvesting practice calls for strips of 8H in windward length. With an estimated baseline flow of 186 mm, such treatment would incresase annual yield by 18% to 221 mm. If the estimation of dominant wind direction is wrong, windward lengths along the strips could reach 15H or more, for an estimated water yield increase of less than 10%.
Keywords: Snow management, Timber management, Water yield

Generation of a snow depletion curve for an alpine basin - Buchanan, L. (54th Annual Western Snow Conference, 1986)
Snow depletion curves were generated in the 1985 snowmelt season for an alpine basin, the Green Lakes Valley of the Boulder watershed. The assumption, used in several snowmelt runoff models, of homogeneous snow distribution does not apply to the alpine where wind redistributes snow into discontinous patches. The snow depletion curves were implemented into the Precipitation Runoff Modeling System (PRMS) and describe Snow Covered Area (SCA) recession on each Hydrologic Response Unit (HRU) as it relates to the swe/maximum swe ratio. Snow course data were used 1) in curve estimation, 2) to adjust model snowpack in May and 3) to estimate DSCOR, a model parameter that distributes snow in the accumulation phase. Model performance improved substantially after addition of the snow depletion curves especialy in late season due to prolonging of snow contribution to runoff.
Keywords: Aerial Photography, Precipitation Runoff Modeling System, Runoff Modeling, Snow Covered Area, Snow Depletion Curve

Cost-benefit analysis of airborne gamma radiation snow water equivalent data used in snowmelt flood forecasting - Carroll, T. (54th Annual Western Snow Conference, 1986)
The paper briefly discusses (1) the technique used to make airborne snow water equivalent measurements using natural terrestrial gamma radiation, (2) the errors associated with airborne measurements made over agricultural areas, (3) an estimate of the marginal and total costs to conduct the February 1985 airborne snow survey over Indiana, Michigan, and Ohio, and (4) the dollar benefits directly attributable to the airborne snow survey.Additionally, an estimate of the 1982 flood costs and the subsequent flood protection plans implemented later are discussed. An estimate of the 1985 flood costs is given with and without the implementation of the 1982 flood protection plan and the 1985 airborne snow survey. The various costs associated with the airborne snow survey conducted over the three state region are summarized and contrasted with the dollar benefits obtained as a result of the early flood warnings and forecasts for the city of Fort Wayne and surrounding counties.
Keywords: Airborne snow water equivalent, Cost-benefit analysis, Gamma radiation, Remote sensing, Snowmelt Flooding

Evaluation of the NWSRFs model on a montana watershed - Cooley, K.R. (54th Annual Western Snow Conference, 1986)
In an effort to improve, 1) snow accumulation and melt routines in watershed hydrology models, and 2) water supply forecasting techniques; components of the NWSRFS Model were evaluated using data from a Montana watershed. Specifically, the snow sub-model HYDRO-17 was tested against data from two snow pillow sites, and additional sub-models relating to soil moisture, unit hydrographs, and stresamflow routing were tested against streamflow from the Lower Willow Creek Basin in southwestern Montana. Relationships between snow pillow site and zonal snow water equivalent are presented. Also presented are methods used to arrive at preliminary estimates of some model parameters, assumptions used to develop needed snow pack volume, and variability of parameters with time and area of consideration. Results emphasize the importance of on-site data, and the expedience of properly locating precipitation and snow water equivalent monitoring equipment.
Keywords: NWSRFS, Runoff Modeling, Snowmelt Runoff

Identifying and comparing organic carbon source areas in an alpine watershed - Hoffman, K. (54th Annual Western Snow Conference, 1986)
Spatial patterns and variation in dissolved organic carbon (DOC) concentration and mass flux were identified in a 7.1 km² alpine basin during the 1985 snowmelt season. Two all-basin reconnaissances were conducted, one prior to and one following peak discharge. Chemical data collected at 98 sites included surface water temperature, pH and specific electrical conductance. Laboratory analysis for DOC revealed values ranging from 0.47 = 8.60 mg C/l. DOC concentration differences between north v. south-facing slopes---and---the lower v. upper basin were not as marked as expected. Mass flux levels showed greater contrast with a strong control by discharge. Of environmental influences on DOC, slope angle displayed the strongest control. Tundra grass commuities produced the highest concentrations among vegetation types. Elevation and slope aspect were shown to be poor predictors of DOC concentration.
Keywords: Organic Carbon, Snowpack Chemical Analysis

Problems associated with the variability of southwest precipitation and seasonal snowpacks - Jones, R.; Brazel, A.J. (54th Annual Western Snow Conference, 1986)
The effects of variability in the general climate of Arizona are considerable on snowpack conditions and resultant runoff from major watersheds of the region. The limited predictability of these conditions exacerbates problems of surface water management. Long term planning for surface water resources and analyses of seasonal snow conditions must be based on a reporting scheme that considers appropriate definitions of normals.The precipitaton regime and snowpack conditions of Arizona can be characterized as consisting of many dry years interspersed by extremes of wetness. This kind of regime lends itself to employing measures such as the median as a representation of the most frequent or normal condition. The current reporting of snowpack and precipitation relative to the mean or average long term condition may misrepresent the interpretation of an individual yearly pattern in the context of the long term expected snowpack and precipitation climate of the Southwest region.
Keywords: Arizona, Median, Precipitation variability, Snowpack climatology

Snow compaction effects of nighttime freezing - Kattelmann, R.C. (54th Annual Western Snow Conference, 1986)
Artificial compaction of snow is amoung the most drastic of our snow management and engineering techniques. Snow is compacted to improve recreational skiing conditions; to create winter roads, parking lots, and runways; and for use as building material. Compaction increases both the density and hardness of snow. As part of a study to assess some of the hydrologic effects of snow compaction at ski areas, nighttime freezing depths of both compacted and natural snow were measured at two Sierra Nevada sites. The degree of nocturnal refreezing of the snowpack affects the timing of meltwater release on the following day and may partially account for observed differences in runoff from compacted and natural snow. The compacted snow froze an average of 13 cm deeper than the uncompacted snow, based on 16 pairs of measurements. The greater depth of freezing of the compacted snow can be explained by the increase in thermal conductivity with increased density and bonding.
Keywords: Refreezing, Snow Compaction

Snowmelt runoff simulation using a degree-day and nonlinear multiple recession model - Kim, S.; Busch, J.R.; Molnau, M. (54th Annual Western Snow Conference, 1986)
A snowmelt runoff model was developed using (a) the degree-day method and (b) a nonlinear multiple recession equation. The nonelinear multiple recession equation was derived using the concepts of superimposition and three nonlinear sequential recessions. The developed equation is infinite and nonlinear, and accounts for delay and attenuation of the runoff process. The derived equation simulates the total runoff hydrograph without separating the runoff into a number of runoff components. For snowmelt estimation, the degree-day factor is determined using computed and observed snow cover data. The model was applied to the Snake River basin above Heise (14,900 km2) for eleven snowmelt seasons. The average volumetric difference between computed and the observed runoff was within one percent and R square was 0.91. The model appears to be effective for operational snowmelt runoff forecastiang as the timing of low and high runoff matches the observed.
Keywords: Multiple Recession, Operational Forecasting, Recession, Snow Cover, Snowmelt Runoff

Persistence of soil moisture changes resulting from artificially extended snowmelt - MacDonald, L.H. (54th Annual Western Snow Conference, 1986)
Snow redistribution due to forest harvest has been extensively studied in the Sierra Nevada, and several public utilities are conducting cloud-seeding programs. The effectiveness of such management actions in increasing summer runoff was investigated by simulating extended snowmelt on four 960 sq m plots using a gravity-flow irrigation system. Intensive groundwater and soil moisture monitoring was carried out on two of these treated plots, two adjacent control plots, and in the areas between the plots and the first-order stream. Shallow piezometers indicated a rapid response to the simulted snowmelt and a sharp decline in water levels after treatment ceased. Tensiometer and soil moisture block data indicated that soil moisture differences may persist for several weeks compared to the control plots, and that this effect may extend downslope under certain conditions. The persistence of this change in soil moisture suggests a physical basis for claiming an increase in mid- and late summer streamflow.
Keywords: Artificial Snowmelt, Cloud Seeding, Soil Moisture

Parameter estimation for the precipitation runoff modeling system using snow course and snow telemetry system data - Marron, J.K. (54th Annual Western Snow Conference, 1986)
A distributed parameter, deterministic, physical process model known as the Precipitation Runoff Modeling System (PRMS), developed by George Leavesley of the US Geological Survey is used to determine the feasibility of using telemetered as well as manually measured snowpack and precipitation information to develop a forecasting tool for use in the East Fork of the Carson River, Nevada. Sources of error in streamflow simulations are a result of the incorrect indentification of the form of precipitation, and the simulation of the highly variable distribution of precipitatioN and air temperature on the watershed. Procedures that identify the form and improve the distribution of precipitaton on the watershed are developed and tested. A probability analysis technique developed for use with PRMS is reviewed and possibilities for its application and further development are discussed.
Keywords: Precipitation & Temperature Distribution, Precipitation Form, Probability, SNOTEL

Precipitation and snow water equivalent sensors: an evaluation - McGurk, B.J. (54th Annual Western Snow Conference, 1986)
Telemetry is a major source of snow water equivalent and precipitation data, but questions remain as to the sensors' accuracy and reliability. Hourly measurements at the U.S.D.A. Forest Service's Central Sierra Snow Laboratory, near Soda Springs, California, provided the basis for a comparison of data from a snow pillow, a precipitation storage gauge, and a weighing rain gauge during water years 1984 and 1985. These data were supplemented with meteorologic data and manual snow measurements for seven events that lasted 6 or 7 days and deposited 5 - 18 cm of moisture. Analysis showed that 2 - 6 hours often passed before the pillow registered new snow and 12 - 48 hours often passed before the total storm amount registered; the 46 cm storage gauge overmeasured while the 20 cm weighing gauge undermeasured; variations in sensor excitation voltages produced 2 cm depth fluctuations; and the storage gauge occasionally registered the bulk of a storm's precipitation 6 - 24 hours after the storm ceased or showed 5 cm increases when no precipitation occurred.
Keywords: Precipitation, SNOTEL, Snow pillows, Snow sensors

Consumptive loss from manmade snowmaking - Mills, K.; Eisel, L.M.; Leaf, C.F. (54th Annual Western Snow Conference, 1986)
Colorado Ski Country USA has undertaken a two year Management Research Study (October 1983-September 1985) designed to investigate the amount of consumptive water loss due to manmade snowmaking. This research has been divided into two studies: (1) the initial loss which occurs at the snowmaking machine, and (2) the watershed loss which occurs during the time the artificial snow resides in the natural snowpack and is subject to evaporation and sublimation loss. The initial loss was estimated using data gathered during field experiments and used as input to three models: (1) a blowing snow model, (2) a thermodynamic energy balance model, and (3) a mass balance model. Estimates on the amount of consumptive loss during the watershed loss phase were estimated by employing the Leaf/Brink Hydrologic Simultion Model of Colorado Subalpine Forest. Six Colorado ski areas were instrumented to collect data required to simulate runoff from their watershed. Once calibrated and validated to an area, precipitation input was changed to represent artificial snow and simulation runs were made to estimate consumptive loss during dry, average and wet years.
Keywords: Consumptive Loss, Ski Area Snowmaking, Snowmaking

Estimating snow course water equivalent from SNOTEL pillow telemetry: an analysis of accuracy - Palmer, P.L. (54th Annual Western Snow Conference, 1986)
Regression analysis between SCS SNOTEL snow pillow and manually measured snow course data allows estimates of snow course water equivalent to be made directly from pillow telemetry. The regression equations were based on data collected over a five year period at 62 snow data collection sites in Idaho.Actual snow course measurements taken during the 1985 snow season were compared to estimates made from snow pillow telemetry. The residuals were divided into accumulation season and melt season categories. In both cases, errors were normally distributed around the mean. Accumulation season estimates had an average absolute error of 5.6 percent and a standard deviation of 9.5 percent. During the melt season, errors were higher and more widely distributed, with an average absolute error 11.8 pecent and standard deviation of 21.4 percent. This analysis provides the necessary relationship to update streamflow forecasts at any time of the month using real-time telemetered data. Examination of estimating error provides a basis for sensitivity analysis of forecasts based on telemetered data.
Keywords: Estimating snow course data, SNOTEL, Snow course, Snow pillow

Probabilistic prediction of snow loads on sloped roofs - Sack, R.L.; Pinkard, J.J. (54th Annual Western Snow Conference, 1986)
Snow loads on sloped roofs are influenced by roof slope, roof surface, snow properties, and meteorological conditions. A statistical model of the snow accumulation and sliding processes for slippery roofs is developed using field data for the winters of 1983-84 and 1984-85 from six prototype shed roofs with varying slopes. The predictive model uses temperature as the primary indicator of sliding and incorporates sliding both at the roof surface and within the roof snowpack. Roof snow loads at four different geographical locations are simulated using the model and 25 years of meteorological data. The ground-to-roof conversion factors for sloped roofs Cs, as proposed by the American National Standards Institute (ANSI) are compared with those predicted by the simulation. The results indicate that Cs is affected by climatological differences, and the values of Cs as given by ANSI are condiderably higher than the simulated coefficients.
Keywords: Probabilistic snow loads, Roof snow loads, Simulated roof snow loads, Slippery roofs, Snow sliding

Spatial and temporal variability in forest soil frost development in western Montana - Saul, L.A.; Potts, D.F. (54th Annual Western Snow Conference, 1986)
Systematic sampling grids of methylene blue frost tubes were used to study temporal and spatial characteristics of soil frost development in a 1250 m elevation forest stand and adjacent clearcut in western Montana during the winter of 1985-86. The inverse relationship between snow accumulation and frost depth is very strong. Consequently, the influence of forest canopy on snow accumulation resulted in greater frost depth in the stands than in the adjacent clearcuts. There was a difference of almost 80 days in the timing of maximum frost depth between the two elevations. Relative variability in frost development (indicated by the coefficient of variation) was nearly identical and constant on the low site treatments, and very similar but not constant through the winter on the high site treatments. Frost will be gone before snow on the high sites. Snow was gone before thaw began on the low sites.
Keywords: Frost Depth, Soil Frost Development

A centralized forecasting system for the western United States - Shafer, B.A.; Huddleston, J.M. (54th Annual Western Snow Conference, 1986)
As a result of a reorganization in the Soil Conservation Service (SCS) Snow Survey Program in 1983, a number of functions including streamflow forecasting, data base support, hydrologic modeling, and report generation were assigned to the West National Technical Center in Portland, Oregon. To fulfill these responsibilities, a Data General MV-8000 minicomputer was acquired and a centralized forecasting system (CFS) designed and implemented on it that supports snow survey activities in 12 western states. Within CFS, an operational data base consisting of daily and monthly time series data has been created. Access to CFS is provided to other federal and state agencies as well as the general public through both asynchronous and synchronous communications. CFS is conceptualized as the primary focal point for snow survey data collection, data exchange, and forecast product dissemination. It is being integrated into SCS' Field Office Communication and Automation System (FOCAS) implementation plan to help expedite delivery of planning information to local users.
Keywords: Forecasting system, Hydrologic data bases, SNOTEL, Streamflow forecasting, Water management planning

Managing snow to extend the areal range of winter wheat production - Steppuhn, H.; Nicholaichuk, W. (54th Annual Western Snow Conference, 1986)
Snow possesses excellent insulative properties, its use in the construction of igloos is legend, its cold-temperature protection for over-wintering crops well known, indeed, in climates where winter air temperatures commonly dip below -20 degrees C, the occurrence, persistence and uniformity of snowcovers dictate the areal range within which winter wheat can be profitably produced. In this study, snow management practiced over a five-year period extended the range of winter wheat into an area where the crop traditionally could not always survive the winter. Two management techniques were tested; tall wheatgrass barriers for annual cropping and chemical fallow for biennial production. Although the winters of 1983-84 and 1984-85 proved extra difficult for the survival of many overwintering crops, wheat grown under snow management wintered well and yielded satisfactory economic crops. This test demonstrated the merits of snowcover enhancement for winter wheat survival in a cold climate and the extension of wheat production into regions hitherto marginal.
Keywords: Chemical fallow, Grass barriers, Snow management, Snowcover enhancement, Winter wheat survival

Snow fencing to increase streamflow: preliminary results - Sturges, D.L. (54th Annual Western Snow Conference, 1986)
A 3.8-m-tall snow fence 800 m long was placed on a 307-ha sagebrush-covered watershed in southern Wyoming in a paired watershed study. Snowmelt discharge increased 137%, snow accumulation increased 58%, and runoff was lengthened 18 days, over values predicted by pretreatment regression relationships the first 2 years after treatment. Overall water yield efficiency of snow stored in the fenced section was 32%, but yield efficiency of additional snow stored by the fence was 85%. Placement of additional snow over natural snow accumulations maximized water yield efficiency. The fence trapped virtually 100% of blowing snow.Average suspended sediment concentration in water was less than 11 mg/liter and deposition of coarse sediment was less than 0.11 cu m/sq km before and after fencing. Specific conductance of water ranged between 150 and 760 micromhos/cm at 25 degrees C; approximately 40% of the water samples had a conductivity between 300 and 400 micromhos/cm.
Keywords: Snow fences, Snow management, Specific conductance, Suspended sediment, Water yield improvement

Snow accumulation and ablation on adjacent forested and clearcut sites in southeastern British Columbia - Toews, D.A.A.; Gluns, D.R. (54th Annual Western Snow Conference, 1986)
A synoptic survey of adjacent forested and clearcut sites was undertaken to determine differences in snow accumulation and rate of ablation and to investigate regional patterns with respect to elevation and aspect. Snow accumulation as measured on 60 sites over a 3 year period averaged 37% greater on clearcut sites whereas snow ablation rates as measured on 15 sites were 38% faster. Synoptic relatioNships of accumulation to aspect and elevation were generally weak. Local comparisons between adjancent north and south slopes indicated a 16% greater accumulation on north slopes than south slopes. The weekly snow ablation rates varied between aspects with peak seasonal ablation occurring earlier on the south aspect than the north aspect. Also, the snow disappearance was 7 and 14 days earlier on the south than the north forest and clearcut, respectively. These differences in melt rates and disappearance dates between high energy and low energy aspects can be used to purposefully desynchronize water delivery to channels.
Keywords: Snow ablation, Snow accumulation, Timber harvesting

The effect of patch clearcutting on the water balance of a subalpine forest slope - Troendle, C.A.; Meiman, J.R. (54th Annual Western Snow Conference, 1986)
Peak water equivalent in the snowpack, soil moisture content before, during, and after snowmelt, and soil moisture content during the growing season were monitored on three adjacent study plots on a 35 percent north-facing slope. After 2 years of calibration, the center plot was clearcut, creating a 4-tree height opening in the 20-m stand. During the next 3 years, up to 50 percent more snow water equivalent accumulated in the opening than in the upwind control. This increase is evident both for individual events and for the entire season. The increases occurred primarily during the snowfall events, where no measurable redistribution occurred between events. Soil water recharge in all plots was not affected by clearcutting. However, significantly less soil water depleted (-5.1 cm) from the clearcut plot than from either the up or downwind forest after harvest. Increased snowpack accumulation in the opening accounted for 14.8 cm of the estimated 19.9 cm increase in water available for streamflow for the clearcut; reduced soil water depletion accounted for the remaining 5.1 cm.
Keywords: Clearcutting effects, Soil water recharge, Subalpine forest

Snowmelt hydrograph separation: Chemical and graphical methods compared - Woo, S.; Berg, N. (54th Annual Western Snow Conference, 1986)
In the semi-arid United States, snowmelt runoff has historically supplied high-quality water for domestic, industrial, and agricultural uses. Yet snowmelt runoff may carry atmospheric and terrestrial pollutants, the fate of which is tied to runoff volume and flowpath. Flowpath information is also required in snowmelt prediction models. In a study conducted at a small mountain watershed near Donner Summit, California, water chemistry and discharge data were gathered to compare chemical and graphical techniques of snowmelt hydrograph separation. From the graphical approach, estimated seasonal baseflow is approximately 12% of total flow. Given measurement uncertainties for discharge and total dissolved solids (TDS), predictions from the two methods agreed fairly well. However, the chemical method estimated seasonal baseflow to be 32% of total flow. This percentage is likely an overestimate, considering the shallow soils and granitic bedrock of the experimental watershed. Overestimation from the seasonal chemical method is attributed to the assumption that baseflow TDS is constant.
Keywords: Chemical Analysis, Total Dissolved Solids, Water Chemistry

1985 Title, Contents, and Minutes (53rd Annual Western Snow Conference, 1985)