Regional Non point Source Organic Pollution Modeling and Critical Area Identification for Watershed Best Environmental Management

In order to implement best environmental management practices in agricultural watershed, it is necessary to evaluate non point source pollution loads and identify critical watershed pollution sources, which are regional management priority missions. Nutrient related non point source pollutant inputs can increase primary production and intensify water eutrophication. Not all watershed areas are critical and responsible for high amount nutrient pollution losses. Implementation of watershed environmental prevention is required to assess pollution yields. Further more, identification of these critical areas is essential for the effective and efficient implementation of watershed best environmental management. In this study, a geographic information system based Soil and Water Assessment Tool was applied in Bahe River watershed, a part of the Yangtze River basin. Land use, soil series texture and daily rainfall data for a 10-year period (1996-2005) was used in this study. The calibrated model system was verified to estimate average annual Organic Nitrogen and Organic Phosphorus yields in these 10 years. The estimated results were also tested and optimized by statistical software. Based on 10-year average yearly Organic Nitrogen yield and Organic Phosphorus losses, critical sub-watersheds were identified. The five sub-watersheds in the north part of watershed were under more intensive pollution yield, west group sub-watersheds contributed to moderate losses, whereas other sub-watersheds fell under slight loading classes. The research outputs developed a basis for an effective watershed environmental management plan. The study revealed that the Soil and Water Assessment Tool could be applied successfully for identifying critical sub-watersheds for watershed best environmental management purposes.