Application of the APEX Model to Determine Water Quality Assessments in Agricultural Fields in the Mississippi Delta

Ramirez-Avila, J. J., Ortega-Achury, S. L., & McAnally, W. H. (2012). Application of the APEX Model to Determine Water Quality Assessments in Agricultural Fields in the Mississippi Delta. Mississippi State University: Geosystems Research Institute, #4010. 62 pp.

The lack of information in many regions regarding watershed monitoring for water quality and quantity and their associated costs, has promoted the frequent use of analytical tools, such as empirical and dynamic hydrologic and water quality models to explore actions and policy alternatives for managing both, water quality and quantity from intensive agricultural fields. The evaluation and selection of appropriate applicable analytical tools has been identified as one of the strategies needed for designing, siting and assessing the potential reductions from multiple management practices implemented within the Mississippi Delta region. The present study is a component of the activities oriented to the evaluation and selection of those appropriate analytical tools. The study was conducted to predict, using the Agricultural Policy Environmental Extender (APEX) model, the effect of changing land use and management practice scenarios on runoff quantity/quality and crop productivity in an 11.3 ha agricultural subwatershed located in the Mississippi Delta region. A model performance was initially evaluated by comparing predicted results over four years of monitoring information for daily, monthly and annual runoff depths, sediment and phosphorus loads, soil properties and crop productivity changes under reduced tillage practices. Accurate results were obtained in this study under the need to calibrate a non extensive number of input parameters. This condition infers that the APEX model structure and components, along with detailed specific site information make the model a strong useful tool, capable of simulating conservation practices and scenario analysis for evaluating the impacts of conservation programs under agricultural production in the Mississippi Delta region. Further research with additional data sets is needed to evaluate the applicability of APEX for other cropping and conservation practice conditions in the region, including expanded soil samples and runoff depth and quality, use of organic amendments, and best management practice effectiveness measurements. The APEX model can be satisfactorily considered as an appropriate tool at field and watershed scales to develop action plans to enhance the nutrient reduction strategy within the Mississippi Delta region.