I N D I N G S
RESOURCES AND ENVIRONMENT
Over 75,000 reservoirs in the 48 contiguous States provide
recreation, scenic beauty, flood control, fish and wildlife habitat,
water supplies, hydroelectric power, and other benefits. But over
time, sediment settling to the bottom of reservoirs reduces their
water-holding capacity and the quality of benefits they provide.
Agricultural runoff is a major source of reservoir sediment in
many areas of the country. Sediment washed from fields moves
down streams and settles in lakes and reservoirs. Therefore, steps
to reduce soil erosion on the Nation’s farms and ranches can
protect the benefits provided by reservoirs.
A recent analysis by ERS estimates that the value of a 1-ton
reduction in agricultural soil erosion and the subsequent reduc-
tion in reservoir sedimentation is as high as $1.38 per ton. The
analysis provides per ton benefit values for all of the 2,111 water-
sheds in the 48 contiguous States. Benefit values across the
country vary because of site-specific differences in the physical
effects, that is, the quantity of sediment deposited due to a
1-ton change in soil erosion, and the value people place on
changes in reservoir benefits. In general, as the number of
reservoirs within a watershed increases, physical effects increase.
As the size of the population affected in a region increases, the
total value of benefits increases. Consequently, benefit values
tend to be higher in the East.
The ERS estimates of the benefits of soil conservation, in
terms of their impact on reservoirs, are derived from two models.
The first links changes in soil erosion to changes in reservoir sed-
imentation, using data on reservoir characteristics, sedimentation
rates, and erosion rates. The second model links changes in the
value of reservoir benefits to changes in reservoir sedimentation
and is estimated with data on reservoir characteristics and,
indirectly, dredging costs. The analysis estimates a benefit model