GIS-Based Decision Making Analysis of Nonpoint Source Pollution Management in Zhangxi River Watershed, P.R. China

The main objective of this study was to construct and assess comparatively management scenarios in Zhangxi River watershed located in Zhejiang, China, applying the annualized agricultural nonpoint pollution source model (AnnAGNPS) integrating with ArcView GIS software. Parameter sensitivity analysis was performed, and those parameters that exerted a significant influence on the output variables were obtained. The spatial distribution of NSP load information was obtained using AnnAGNPS simulation. Based on the results of sensitivity analysis, the NSP load spatial distribution and the local conditions, five alternative scenarios for nonpoint pollution control were constructed and evaluated through AnnAGNPS simulating. Results showed that scenario 4, conversing longitudinal farming to contour farming was the most effective for controlling NSP load in the case. And it was followed by scenario 1, with the characteristic of returning cultivated land to forests. The reduction of fertilizer and building grass filter belt had relatively less influence on sediment and nonpoint source pollution load. The optimal strategies obtained would help the local watershed manager to make the best management practices and provide them with a decision support.