Study On Water Environmental Capacity Incorporating Nonpoint Source Pollution Load

The water environmental capacity is the ability for water to accommodate the pollutants. is an important basis of water environmental planning and management, but also is useful strategy to solve water pollution problems and achieve water quality optimization management. With the development of the domestic economy and Point Source Pollution gradually brought under control, Non-point Source Pollution become more grave than before.In this research, we firstly summarize the domestic and foreign research progress and related concepts of the water environmental capacity, then we choose Gongjing District section of Xushui River as subject investigated, use Arcgis divide the entire basin into18sub-basins, research the water environmental capacity separately, the results are as follows:1. Graphics and data of the research region obtained through surveys. Graphics include DEM, river data, land-use data by Arcgis, data include population, livestock and poultry.2. monitored and evaluated the water quality, using of export coefficient method to estimate each sub-basin ’s pollution load, the results demonstrate as follows:the COD output quantity was8490.34t/a, the amount of pollution load into the river was2203.94t in the high-water period,755.64t in the normal-water period, and ignore the non-point source in the low-flow period, the TP output quantity was46.05t/a, the amount of pollution load into the river was14.39t in the high-water period,4.99t in the normal-water period, and ignore the non-point source in the low-flow period, the TN output quantity was615.48t/a, the amount of pollution load into the river was205.16t in the high-water period,61.55t in the normal-water, and ignore the non-point source in the low-flow period. According to the urban and the situation of the coastal pollution, the results was the COD output quantity was839.83t/a, the amount of pollution load into the river was545.89t/a, the TP output quantity was18.04t/a, the amount of pollution load into the river was11.73t/a, the TN output quantity was553.16t/a, the amount of pollution load into the river was359.55t/a.3. Choose the proper evaluation model and made scientific evaluation of the parameter in this research. The COD water environmental capacity was-1853.62t in the high-water period,-911.142t in the normal-water period,-246.15t in the low-flow period, the TP water environmental capacity was-18.69t in the high-water period,-1.06t in the normal-water period,2.47t in the low-flow period, the TN water environmental capacity was-308.21t in the high-water period,-205.43t in the normal-water period,-101.71t in the low-flow period. The COD water environmental capacity and the TN water environmental capacity was negative, the TP water environmental capacity was positive only in the low-flow period, the TP water environmental capacity sort by size was that: the high-water period<the normal-water period<the low-flow period. This result depended on the high water function target, and also related with the high non-point source pollution, rainfall and flow.4. The results showed that Gongjing District section of Xushui River’s pollution is serious, need to take effective measures to improve the situation. Then base on the comprehensive result of Gongjing District section of Xushui River, the view of careful and rational use or reduce of water environmental capacity and some suggestions to control and improve the water quality were referred.5. The results calculated by the model of water environmental capacity and the actual situation were basically same. Due to non-point source pollution has complexity, randomness, etc., need to collect and analyze large amounts of data, because of the limitations of information and time in this study, some of the data and parameters are obtained by estimating, it must have a certain bias with the actual specific data, so the methods and the results must studied and improved in the further.