A Sensitivity Analysis of Impacts of Conservation Practices on Water Quality in L’Anguille River Watershed, Arkansas

Assessing the performance of appropriate agricultural conservation practices (CPs) frequently relies on the use of simulation models as a cost-effective tool instead of depending solely on the monitoring of water quality at individual field and watershed levels. This study evaluates the predicted impacts of several CPs on nutrient and sediment loss at the hydrological response unit scale in the L’Anguille River Watershed, which is a watershed identified as a “focus watershed” under the Mississippi River Basin healthy watershed Initiative (MRBI) program. The Soil and Water Assessment Tool model was calibrated and validated between 1998–2005 and 2006–2012, respectively for flow, sediment, total phosphorus, and nitrate nitrogen. Out of the seven MRBI CPs modeled in this study, the highest reduction in sediment (80%) and nutrient (58% for total phosphorus and 16% for total nitrogen) was predicted for the critical area planting practice, followed by filter strip, irrigation land leveling, grade stabilization structure, irrigation pipeline, nutrient management, and irrigation water management. Some of the predicted impacts conflicted with expected CP performance. The study underscores the importance of the proper formulation of CP algorithms in using simulation models for predicting impacts on water quality.