Column: No snow, no water. know snow, know water
As an incredible ski season winds down all eyes are looking toward our rivers and streams in anticipation of summer rafting, fishing, and the start of the irrigation season. Farmers and ranchers, municipal and industrial water suppliers, and recreation companies must make important decisions based on the water supply predictions. There is one source of information that has provided this important data for nearly 50 years—the Natural Resources Conservation Service (NRCS) Water and Climate Center.
Throughout the Mountain West, the NRCS Water and Climate Center operates over 700 Snowpack Telemetry Sites (SNOTEL). These automated sites collect snowpack and snow water equivalent (SWE) measurements which are used to forecast the available water supply for a watershed under the varying climatic conditions experienced from year to year. The water supply forecast is a prediction of the volume of water anticipated to runoff, generally from April through July.
The first known attempts to measure the snowpack date back to 1834, with early settlers acknowledging the importance of snowpack. In 1906, Dr. James Church, a professor at the University of Nevada in Reno, established the first systematic snow survey. The snow survey used two simple measurements: snow depth and SWE, which are used to determine snow density. SWE is the amount of water contained within the snowpack and provides insight into the amount of water available to produce the summer runoff as the entire snowpack melts off.
These measures proved to be a suitable way to forecast the next season’s water supply. The techniques quickly caught on, spurring other entities to take it upon themselves to implement snow surveys, providing important information to water users throughout many western states.
Following the Dust Bowl, farmers and other water users demanded better predictions of stream flows. In 1935, Congress enacted a federal snow survey and water supply forecasting program, which has evolved into the SNOTEL system in place today.
The ideal location to measure snowpack is in a forested clearing which acts to break the wind and allow snow to accumulate with minimal drifting. Located in remote, high mountain meadows, sites are selected to best represent snowpack for a watershed. Access to the snow course often requires snow shoes or skis.
NRCS relied on manual snow courses until the first automated SNOTEL site was established in the early 1970s. Snow courses entail collecting snow depth and core samples over a representative area using a hollow aluminum tube, known as the federal sampler. Each core sample is weighed with a scale. The weight of the sample determines the SWE. Manual surveys are conducted once a month. With demands or more accurate information, more frequent measurements are needed to accurately predict water availability using a greater number of locations
The advent of the SNOTEL network in the early ’70s enabled the collection of near-real time data. They operate unattended and without maintenance for a year or longer with batteries charged by solar cells. The information obtained from SNOTEL sites is then transmitted back to the master data stations — located in either Boise, Idaho or Ogden, Utah — via meteor burst radio wave communications. With a low-powered transmitter and a simple antenna, data from SNOTEL sites update on an hourly basis and are accessible to the public via the NRCS’s website.
Manual snow surveys are still used in conjunction with the automated SNOTEL data, in some cases to ground truth the automated sites. Local NRCS employees and personnel from partner agencies go out monthly during the winter and collect data at snow survey courses in the area. Living in an arid climate, 50-85 percent of our annual water supply is stored in the winter snowpack “reservoir.” With most of the water supply in the West arriving in the form of snow, snowpack monitoring and water-supply forecasts provide much needed information to water users and planners and are critical for determining reservoir operations from year to year.
As water demands continue to increase and climatic conditions continue to add uncertainty to our water supply, the services provided by the NRCS will be increasingly important. For more information and access to SNOTEL reports, please visit the NRCS SNOTEL website at http://www.wcc.nrcs.usda.gov/snow.
The Bookcliff, South Side and Mount Sopris Conservation Districts provide technical, financial and educational resources to local land users for the conservation of soil, water and related natural resources. To find out more, please visit our website at http://www.bookcliffcd.org.
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