Modeling Best Management Practices in a Small Watershed Using Process Based Modeling Approach

Soil erosion is a problem that causes both the loss of valuable soil and water quality degradation by sediment and attached nutrients and pollutants. Soil loss and sediment discharge to waterbodies can be prevented and mitigated by best management practices (BMPs). A number of researchers have investigated the effectiveness of BMPs and demonstrated the positive roles of the BMPs. However, there are a number of challenges and uncertainties in modeling and assessing of BMPs. These include model representation methodologies, validation, and scale issues.

This study includes measured data analyses and representation of BMPs such as row cropping, filter strips and grassed waterways in a small experimental watershed (2.09 ha) at Nelson Farm, MS from 1990 to 1995. A total of three phases were established according to the BMP implementation schedule. The WEPP (Water Erosion Prediction Project) model and its parameters including physically based parameters are used and adjusted for the representation of BMPs. The parameter setting for the vegetative practices were calibrated and validated to agree with observed data at the location of the practices in each phase. There are two WEPP projects depending on two different flow paths, one is based on flow along the cropping row and the other is based on flow over the crop rows when the rows are collapsed by large runoff events after tillage.

The Soil and Water Assessment Tool (SWAT) was run with the same watershed properties and parameter settings. Various scenario analyses also have been conducted. These include the failure of BMPs, the effectiveness of a combination of BMPs, the long-term impacts of BMPs, and spatially distributed estimation of the effectiveness of filter strips.