Snow Surveys and Water Supply Forecasting

Summary

The major reason for the snow survey program with its extensive data collection network has always been the forecasts of annual streamflow volume at specific points along a river system. These forecasts are a vital input to water management. Irrigation, reservoir operation, domestic water use, power generation, fisheries management, and flood control are typical of the activities dependent on streamflow (fig. 16). Others are concerned with the actual measurements rather than forecasts, and the management of certain resources such as wildlife and range can be tied directly to these data (fig. 17). Traditionally, information has been distributed by NRCS in each State through the monthly mailing of printed water supply outlook reports from January through May. Also, water supply products for the Western United States (including snowpack, precipitation, and streamflow forecast maps) produced jointly by the NRCS and the National Weather Service are available from their respective web sites for the same period. The final product for the water year is an annual snow data summary. Snow data are maintained in a national archive.

Figure 16. Reservoirs such as Lake San Cristobal in Colorado are dependent
on streamflow.

Figure 17. Range management
can be tied directly to annual
streamflow volume data.

The modern snow survey program, with real-time data provided by SNOTEL and CFS, is delivering a broader range of more timely information than is possible with printed reports. And the information is keyed to the specific needs of NRCS and conservation district offices and an expanding user community: news media, civic organizations, emergency agencies, recreation manager, and others.

Resources management agencies such as USDA's Forest Service, U.S. Department of the Interior's Bureau of Land Management and Bureau of Indian Affairs, or State departments of fish and game and forestry require up-to-date water supply information. CFS presents opportunities for NRCS to work cooperatively with these agencies to accomplish soil and water conservation objectives.

Demands are increasing for the often limited water supply in the western river systems (fig. 18), and forecasts must be as current and reliable as possible. The computer access provided through CFS not only makes the latest data instantly available, but it provides many standard and customized analysis procedures to support specific needs for information.

Figure 18. Many Americans mistakenly
believe that there is an inexhaustible
supply of water. But even rivers like the
Gallatin River in Montana face increasing
demands for this limited resource.