Vegetation Buffer Strips Design Using an Optimization Approach for Non-Point Source Pollutant Control of an Agricultural Watershed

Management of agriculture-induced water quality problems requires an integrated approach involving selection of the most suitable and economical Best Management Practices (BMP). Vegetation Buffer Strips (VBS), one of the commonly used off-field structural BMPs, when designed and placed correctly, can significantly improve the water quality. However, VBS takes up agricultural land used for crop production and the implementation/maintenance costs are of concern. Currently, the standards for design of VBS (location and width) are normally set on field study basis, and they do not involve science-based approach to guarantee their efficiency under regional variations, geological and economical conditions. The present study proposes a new approach which integrates computational modeling of watershed processes, fluvial processes and modern heuristic optimization techniques to design a cost effective VBSs in a watershed. The watershed model AnnAGNPS (Annual AGricultural Non-Point Source Pollution Model) and channel network model CCHE1D (Center for Computational Hydroscience and Engineering One(1) Dimensional Model) are linked together to simulate the sediment/pollutant transport processes. Based on the computational results, a multi-objective function is set up, which aims to minimize soil losses, nutrient concentrations as well as total costs associated with installation and maintenance of VBS, while the production profits from agriculture production are being maximized. The solution procedure involves the use of iterative Tabu Search (TS) algorithm to flip VBS design parameters (switching from one alternative to another). The search for the optimal solution follows an iterative procedure. An illustrative case study of USDA's Goodwin Creek experimental watershed located in Northern Mississippi is used to demonstrate the capabilities of the proposed approach. The results show that the optimized design of VBS using an integrated approach at the watershed level can provide efficient and cost-effective conservation of the environmental quality by taking into account productivity and profitability.