Integration of Watershed Model AnnAGNPS and Stream Network Model CCHE1D for the Development of a New GIS-Based BMP Planning Tool

Abstract

This paper presents a new GIS-based Best Management Practice (BMP) tool developed for watershed managers to assist in the decision making process by simulating various scenarios using various combinations of Best Management Practices (BMPs). The development of this BMPTool is based on the integration of a watershed model AnnAGNPS (Annualized Agricultural Non-Point Source) and a stream network simulation model CCHE1D. The impacts of various BMPs on the resulting nutrient loadings in the streams can be monitored at selected monitoring points and different scenarios can be evaluated based on the Environmental and Economic analysis. The application of the BMPTool is demonstrated as a case study in Goodwin Creek Watershed, Mississippi, to evaluate the impact of landuse change and vegetative buffer strips on runoff, sediments and nutrients. Three different scenarios were simulated which included baseline, landuse change and vegetative buffer strips with landuse change. The simulations showed substantial reduction in nutrients and sediment loading when compared with baseline scenario. It is observed that total sediment reduction, in subwatersheds with landuse change and BMP implemented ranged from 0.09 MT to 0.007 MT. At the outlet of the watershed, the total nutrient load reduction in case of total organic nitrogen was from 1.6 MT to 0.4 MT which was further reduced to 0.277 MT in case of landuse change alongwith BMP implementation. Similar trend was observed in case of other nutrients. However, in case of nitrate, about 10% reduction in the total nutrient load was observed.