Runoff Quality Effects of Simulated Conservation Practice Scenarios in a Mississippi Delta's Watershed

Ramirez-Avila, J. J., Ortega-Achury, S. L., McAnally, W. H., & Martin, James L. (2012). Runoff Quality Effects of Simulated Conservation Practice Scenarios in a Mississippi Delta's Watershed. 2012 Mississippi Water Resources Conference. Jackson, MS.

The APEX (Agricultural Policy Environmental Extender) model was developed for use in whole farm and small watershed management with the capability of detailed field scale modeling and routing by connecting farm/field sized subareas. The ArcAPEX is an ArcGIS based user interface designed to automate the input parameterization of the APEX hydrologic/water quality model. The objective of this study is to evaluate runoff quality effects of alternative conservation practices scenarios for agricultural production in a northeastern Mississippi’s watershed using the APEX model and the ArcAPEX interface. Model evaluation compares the observed runoff sediment and nutrient losses from a USGS gauging station draining an 11 ha watershed in the Mississippi Delta with the simulated results generated by APEX. Initial stage of the study demonstrated a satisfactory capability of the model in simulating runoff and sediment at annual and monthly scales (R2≈0.8), but not at daily scale. Using no calibrated parameters, the model underestimated observed phosphorus loading. This maybe due to the use of the initial phosphorus concentration in soils set as zero. Modeling of conservation practice scenarios are expected to evidence an improvement of runoff quality condition at the edge of the studied watershed. Final results are also expected to compare APEX performance with other developed model(s) for the same location and scenarios.