Predicting effects of best management practices on sediment loads to improve watershed management in the midwest, USA

Abstract

Targeted implementation of agricultural best management practices (BMPs) to reduce non-point source pollution is the most recent strategy to improve U.S. surface waters. Little empirical evidence exists documenting effectiveness of U.S. BMP programs at the basin-scale. This knowledge gap hampers the ability of future programs to adapt implementation strategies. Additionally, U.S. agencies may lack sufficient knowledge of upstream processes necessary to plan enhancement of downstream large rivers. This study used the Soil and Water Assessment Tool (SWAT), a deterministic hydrologic model, to predict reduction of sediment erosion and transport over a 30-year period due to grass and woody-riparian establishment on cropland in the La Moine River Basin, U.S.A. Mean annual sediment reduction due to BMPs was predicted to be 3.6% at the downstream watershed gage. Identification of sediment sources in this watershed based on predicted hillslope erosion indicated a cost-effective strategy to reduce sediment load may be constrained by BMP placement primarily in the 100-year floodplain. This study indicated upland areas should be targeted for BMP establishment. Better representation of channel and floodplain sediment processes in SWAT and other hydrological models may be required if BMP targeting in agricultural settings will be assessed by computer simulations instead of on-the-ground monitoring. © 2008 Taylor and Francis Group, LLC.