Non-point Pollution Control of Rural Watersheds in South Taihu Lake Basin
南太湖地区农村小流域非点源污染调控研究

Agricultural non-point source pollution has become increasingly serious due to the development of agriculture during recent years. A multitude of investigations have revealed that non-point source pollution from agriculture and rural regions is the leading source of water pollution in the Taihu Lake basin. In order to control agricultural non-point source pollution and improve water quality, many policies and measures have been formulated and developed. Previous studies stated that the total emission control appears to be effective in abating agricultural non-point source pollution. However, specific measures of effective control of pollutants of the non-point source pollution over rural areas seem to be inadequate, without adhering to the principles of equity, efficiency, and feasibility to reasonably allocate the quotient of the total pollution control to each stakeholder within a rural watershed. The authors investigated the non-point source pollution in the Taihu Lake Basin ranging in elevation between 1.86 m and 2.02 m above the sea level. Rainy season for the basin is generally during the months from April to September, with showing a mean annual rainfall of roughly 1275 mm. An experiment was carried out in April, July, and December in 2007, collecting water samples from the surface runoff in three lakes. The water samples were stored in a cold room and were then equilibrated at the room temperature before analysis. Based on typical output pollutant characteristics of rural watersheds in the Southern Taihu Lake areas, we used the optimized maximum quantity of a pollutant program to calculate the maximum capacity of the water in the rural watershed to retain pollutants and the environmental capacity, and proposed appropriate measures aimed at reducing pollutants. Results showed that the total phosphorus was the major component exceeding its permitted level in pollutants of rural watersheds in South Taihu Lake. The main sources of pollution were rural domestic pollution. Concentrations of agricultural non-point source pollutants were affected by seasonal changes in watershed and environmental factors. Improved water self-purification capacity could effectively mitigate the impact of pollutants on water quality in summer. In addition, the maximum emission calculation method could efficiently optimize the formulation of a rural watershed non-point source pollution control program, which was established by the BAT system.