ABSTRACT:
The high annual cost of damages attributed to sediment justifies the importance of gaining a better understanding of the relationship between the Conservation Reserve Program (CRP) and stream sediment loads. This relationship was studied for two watersheds within the Cache River basin of extreme southern Illinois. CRP enrollments of 15.6% and 26.5% of all cropland in the Big Creek (80.29 km2; 31 mi2) and Cypress Creek (62.16 km2; 24 mi2) watersheds resulted in estimated decreases in erosion of 24% and 37%, respectively. Despite this, it was estimated using path analysis (a two-step regression analysis) that a negligible 0.0125% and 0.265% decrease in sediment load occurred in these streams in the period 1986–1988. These negative results, however, should be viewed in the context of temporal and spatial considerations. First, studies of drainage basin sediment dynamics imply that reductions in suspended sediment in response to CRP enrollments are likely to be delayed for a considerable period as in- and near-stream sediments are remobilized. Second, few of the CRP enrollments were in near-stream locations where hydrologic theory indicates they would be most effective in trapping and stabilizing existing near-stream sediments.
Footnotes
D. Kevin Davie and Christopher L. Lant are in the Department of Geography at southern Illinois University-Carbondale, Carbondale, IL 62901–4514. The authors wish to acknowledge the continuing efforts of local, state, and federal agencies towards a greater understanding of erosion and sediment transport. In particular, this research would not have been possible without the data collection efforts and cooperative attitude toward sharing data held by the regional offices of the USDA Soil Conservation Service and Agricultural Conservation and Stabilization Service, and the Illinois State Water Survey. Thanks Rich, Mike, and Laura.
- Copyright 1994 by the Soil and Water Conservation Society
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