Conservation practice effects on sediment load in the Goodwin Creek Experimental Watershed

Abstract

Water quality and aquatic habitat due to unstable stream channels and high sediment concentrations during storm runoff events are major environmental concerns on the 2,132 ha (5,266 ac) Goodwin Creek Experimental Watershed in north Mississippi. Effects of enrolling erodible lands in the Conservation Reserve Program (CRP) and instream grade stabilization structures were evaluated using measured rainfall, runoff, and sediment concentration data and model simulations. Signatures of naturally occurring radionuclides indicated that 78% of the total sediment load originated from channel sources. The change of land to a CRP-like state (reducing cultivated land from 26% to 8%) reduced erosion and runoff from fields and thus decreased total sediment concentration by 63% between 1982 to 1990. Simulations using the Fluvial Routing Analysis and Modeling Environment model indicated that mean sediment yields would increase from 15% to over 200%, depending upon location in the watershed, if in-channel structures were not present. The combined effect of the grade control structures and the change of lands to a CRP-state was to reduce sediment yields by 78% near the outlet of the watershed.