Snow Surveys and Water Supply Forecasting
Since 1935, most of the American West has relied on the U.S. Department
of Agriculture's cooperative snow survey program for predictions of
meltwater runoff. This program is a Federal, State, and local partnership
directed by the Natural Resources Conservation Service. Its survey
activities encompass Arizona, Colorado, Idaho, Montana, Nevada, New
Mexico, Oregon, Utah, Washington, and Wyoming. Alaska and southern Canada
are partners also. California has an independent program.
Snow surveys in the West date back to around 1906, when the University
of Nevada's Dr. James Church laid out the first western snow course. Dr.
Church also invented key sampling procedures and equipment. The next three
decades saw a proliferation of snow survey activity throughout the West.
In some States, independent power or irrigation companies spearheaded the
surveys; in other States, universities or State engineers were in charge.
Federal leadership of snow survey activities came as a result of the
unprecedented western drought of 1934. Agricultural leaders requested
USDA's help in forecasting water supplies for the ensuing crop-growing
season. Because many of the watersheds and streams were interstate,
Federal help was needed to coordinate the surveys and to develop uniform
procedures and equipment for surveying and forecasting (fig. 5).
Figure 5. The snow surveyors are well-equipped for a
full day's work.
To find out how much water will be available in summer, snow surveyors
from NRCS and the other cooperating agencies collect data from some 1,600
snow courses several times each winter. They determine the depth and the
water content of the snowpack and estimate the amount of runoff from the
In 1977, NRCS began developing a network of automated radio telemetry
data sites for collecting snow survey data. This snowpack telemetry
(SNOTEL) network provides NRCS offices with daily or more frequent
information on streamflow potential. The information is especially
valuable during periods of flood or drought.
The information collected by the telemetry system (see
Remote surveys) and snow surveyors (see
Manual surveys) is translated into water supply forecasts that NRCS
State offices issue monthly from January to June in cooperation with the
National Weather Service. Major sectors of the Western economy --
agriculture, industry, and recreation -- base their plans on these