Soil Moisture Data Short Course

Understanding/Using Mountain Soil Moisture Data

2008 Western Snow Conference – Hood River, OR

A panel of 4 experts in the installation, calibration, verification and use of soil survey and soil moisture/temperature data provide a comprehensive look into the world of soils and the role they play in hydrology and water supply forecasting.

Click on the title of each presentation to open the PowerPoint file in your browser.

Toby Rodgers – Soil Scientist, NRCS Mount Vernon, WA
Working for the NRCS as a soil scientist for the past 7 years and currently Soil Survey Project Leader, National Park Service Lands of WA.
BS in Geology from California State University Sacramento. MS in Soil Science from Washington State University helping to develop the Remote Area Soil Proxy (RASP) model which focuses on modeling soils and landscapes of remote areas such as the Pasayten and Sawtooth Wilderness as well as the NPS project areas in WA, including North Cascades, Rainier, and Olympic National Parks.
Originally from Placerville, CA. Active as a board member of the Washington Society of Professional Soil Scientists, and active as a member of the Surfrider and Snowrider groups, as well as a volunteer baseball coach during the spring.

ABSTRACT - With concerted efforts in recent years to install soil moisture and temperature sensors at climate stations around the west, a growing wealth of data is now available for soil scientists as they create soil inventory maps. Historically, soil data has been very sparse in the western states. Soil moisture and temperature regimes originally designed to describe cropping regimes of the Midwest have been utilized for taxonomic divisions across the mountainous west. Assignment of the regimes is done through correlation of existing vegetation rather than actual data. Having soil climate data at their fingertips will allow soil scientists to assign more reliable taxonomic divisions. To the trained eye, soil taxonomic divisions convey distinctions important to hydrologic modeling of soil-water interactions within a watershed. 
In addition, for each site where sensors are installed, soil samples are being collected to better characterize the variability in soil types and properties. The Natural Resources Conservation Service maintains a soil characterization database with the data from these soil samples (http://ssldata.nrcs.usda.gov/). Samples are collected for bulk density analysis as well as a variety of other physical and chemical properties including available water holding capacity, particle size distribution, and mineralogy. Many of the measured properties are important in correctly classifying soil types as well as understanding the behavior of a soil and its importance to hydrologic models.
Many of the remote areas now being sampled remain devoid of modern soil survey maps from which soil hydrologic properties and influences can be extrapolated. In order to provide the first generation of soil survey information for remote areas, a GIS-based model of soil distribution was developed through graduate research at Washington State University. The Remote Area Soil Proxy (RASP) model utilizes a supervised classification system to sequentially extract soil-landscape associations from digital data layers. Observed soil, pedologic, landscape, and vegetation relationships are rendered digitally to arrive at a meaningful soil distribution map for study areas. These soil distribution maps can ultimately be utilized as a detailed soil hydrologic input for watershed models of hydrology. 

Sheila Strachan – Hydrologist, NRCS Portland, OR
Sheila Strachan has worked as a hydrologist for the NRCS at the Oregon and Washington snow survey office since January 1999. Prior to that, she spent 10 years working for the US Forest Service mapping soils and vegetation communities on the Gifford Pinchot National Forest, and on the Mt. Hood National Forest conducting watershed analyses working in soil and water conservation in the Sandy and Clackamas river basins. She has a BS in Soil Science with a minor in Watershed Management from Oregon State University and an Associates Degree in Forestry and Land Surveying from Paul Smiths College in the Adirondack Mountains of New York State. She has led the installation of soil moisture sensors at 25 SNOTEL sites in Oregon and Washington.

ABSTRACT - NRCS collects mountain climate data at SNOTEL sites throughout the West in support of water supply forecasting. Additionally, the SNOTEL network provides data that is useful for other hydrologic and climatologic applications in natural resources management and research. Soil moisture sensors are one component of in an array of options design to collect and record additional climate information at SNOTEL sites. 
Under the guidance of the National Water and Climate Center (Portland, OR) and the National Soil Survey Laboratory (Lincoln, NE) techniques for site selection, installation and distribution of soil moisture data have been developed. A key component of the installation procedures is a complete lab characterization of soil properties near the soil sensors.

Mark Seyfried – Soil Scientist, ARS Boise, ID
A native Californian, I Attended the University of California and received a BS degree in Soil Science. After 2½ years working as a soil mapper in New Mexico with the (then) Soil Conservation Service, I returned to academia and received a MS and PhD at the University of Florida. After working a year in the tropics on soil water and fertilizer movement under different cropping systems, I went to the University of Delaware to study kinetics of chemical reactions in soils. Finally, in 1988 I landed a position with the ARS in Boise, Idaho at the Reynolds Creek Experimental Watershed and have been working there since 1988. My research interests include soil water measurements and modeling.

Randall P. Julander – Hydrologist, NRCS Salt Lake City, Utah
Snow Survey Supervisor - NRCS USDA - Utah, Nevada and the Sierras of California
BS and MS - Watershed Management/Hydrology - USU
Adjunct Professor, University of Utah, Civil Engineering, Snow Hydrology
General Chair of the Western Snow Conference
A total of 25 years experience in:
SNOTEL and Snow Course data collection
Water Supply Forecasting
Surface Water Supply Indexes
Reservoir Operation Guides
Climatology
Drought and High Flow analysis
Hydrologic modeling
All things Snow and Water!

ABSTRACT - Soil moisture and temperature data are collected at some SNOTEL sites for the purpose of water supply forecasting. Soil moisture is an integral part of the hydrologic cycle. Soils near saturation are capable of producing runoff while those that are extremely dry are not. Soil moisture data may be useful in determining how much of an existing snowpack is required to bring that soil to a runoff or saturated condition. The location of soil moisture sensor sites may play a vital role in the correlation of snow water equivalent, soil moisture and runoff. SNOTEL sites were located primarily based on snow courses that had SWE values that were highly correlated to streamflow. The snow courses themselves were located on a trial and error basis and the ones that were most closely correlated to streamflow were the ones that were kept in the system when others were eliminated. Those sites that have high SWE correlations may not necessarily be those that are most representative of predominant soils or subsurface processes of the watershed. Thus, they may not be an accurate depiction of the absolute value of snowmelt loss to infiltration. Even though some sites may not be representative in a general context, if they remain relational to the dominant soil type or hydrologic process, they still might be useful in an empirical or even a modeling situation. The movement of water through a soil matrix can be very complex. There is the ever present influence of gravity, but there are many other factors as well, such as impervious material, lateral movement, temperature and capillarity. There are the affects of topography; convergence and divergence. Soil physical characteristics such as texture, particle size distribution, organic matter content and pore size distribution play an important role in water movement. Vegetation exerts a critical role in evapotranspiration during the growing season and hence, the residence time capillary water is retained in the soil matrix. A. R. Croft (1946) found that on the Farmington, Utah watershed, (1) practically all water from rains or snowmelt passes through the soil mantle before it becomes available for runoff and (2) the soil mantle has a high capacity to retain water that otherwise would be available for streamflow - 43 to 56 centimeters (17 to 22 inches) of water. From this high elevation watershed study it is apparent that a large soil moisture deficit has the potential to significantly reduce streamflow from snowmelt. Being able to quantify soil moisture in some capacity may lead to a reduction in forecast error. It therefore, becomes important to understand the data being collected and the impacts that various physical characteristics may have on those data.