| Abstract: | In the United States, cropland erosion has decreased by an estimated one billion tons or 42 Percent for the period 1982 to 1997 (USDA NRCS, 1998) through erosion reduction provisions of the Food Security Actof 1985 and the ongoing soil conservation programs administered by the United States Department ofAgriculture's Soil Conservation Service (USDA-SCS), which became the Natural Resources ConservationService (USDA-NRCS) in 1997.The U.S. Geological Survey has measured suspended sediment loads at strearn gages from 198O through1989 and showed primarily decreases of from 1 to 12 percent for most regions and increases for only threeregions, ranging from 2 to l2 percent.A Reservoir Sediment Information System (RESIS) was created so that decades of dare on reservoir sediment deposits could be evaluated (Atwood, 1994, Steffen, 1994; Atwood and Steffen, 1994). Theresults of analyses show a major increase in unit-area sediment deposition rates during the period 1970through 1985, which may be attributable to increased cropland acreage, a switch from diversified farming tointensive monocultUred crops, with widespread adoption of soybeans. The most recent measured ratesshow that 25 percent of the United States reservoirs would be at least half-filled with sediment by 2O18,although there is a significant data gap since 1985. Relatively few reservoirs were surveyed since 1985 dueto lack of funding priority and increased survey labor costs. |
