USING GIS AND MODELS TO STUDY NON-POINT SOURCE POLLUTION IN THE TAIHU WATERSHED

Lake Taihu, the third largest fresh water lake of China, is located in the Changjiang River Delta, the most advanced economic zone in China. The fast growth of the agriculture and industry in last few decades has lead to the degradation of the lake water quality which affects the economic development and people's daily life. The nitrogen and phosphorus pollution sources are mainly farmland, industry, human manure and urine, animal and poultry manure and urine, daily life waste water, and fish ponds. Proportions from these sources are still not been determined. Having comprehensive concept what factor is the major contributor to the pollution is important to protect the water quality.

The geographic information system (GIS) and models including Universal Soil Loss Equation (USLE), Agricultural Non-Point Source Pollution Model (AGNPS), and Areal Non-point Source Watershed Environment Response Simulation (ANSWERS) are used to evaluate the magnitude of agriculture pollution in the lake Taihu. The models will be calibrated. Different data layers being used include land cover, animal population density, topography, soils, hydrology, precipitation, and rainfall-runoff factor. Statistic data and investigation data such as fertilizer application rate, crop yield are considered. Data layers are combined to produce a sediment production index, a runoff index, and nitrogen and phosphorus loading index. The contribution of agricultural non-point pollution to Taihu can be determined with models. The results can also predict the potential pollution due to agricultural activities in the lake water. The results from different models are compared.