Analysis On Water Pollution Character Of South Tiaoxi River Qingshan Lake Basin

South Tiaoxi River, located in Lin'an city, Zhejiang province, is the headwater of Tai Lake. Watershed of Tiaoxi River covers Tai Lake region including Hang-Jia-Hu plain, therefore water quality condition of this River basin imposes direct effects on the residents'health living in this region, and water pollution control to the headwater is of great importance to preventing Tai Lake from contamination. Total pollutant control and non-point source pollution control are the focus of environmental research in the field. The current study has focused on Xi Tiaoxi basin, while the South Tiaoxi River reported rare. Taking South Tiaoxi River as the research object, this study selected South Tiaoxi River Qingshan Lake basin, used an improved fuzzy analytic hierarchy process (FAHP) for water quality assessment. According to the severe pollution of Jinxi River, small watershed of Jinxi River Jincheng segment was selected, material balance method used to calculate water environmental capacity of point source pollution in the river, and used export coefficient method to estimate non-point source pollution loads. The main results are as follows:1) An improved FAHP was established to meet the practical water quality sitiuation and the severity of pollution up to the inferiorⅤwater quality. The improved FAHP took the intermediate value of the upper and lower limits of water quality standards as limited value to compute the degree of membership. In the way, six membership functions were obtained. The eveluation results showed that the major pollutant was nitrogen whose weight coefficient reached 0.487. Each section of water functional areas has exceeded standard seriously. The overall standard-reaching rate was 18.75%. It is a eutrophic River.2) According to the pollution situation about Jinxi River, a tributary of South Tiaoxi River, this article went on studying water environmental capacity of Jincheng segment. Divided research area into several parts, equilibrium relationship w deduced water environmental capacity model. NH3-N and COD were selected as evaluation indexes to analysis its environmental capacity. Typical hydrological years were calculated by fitting curve method and hydrological analogy method. Combining with hydrological characteristics of Lin'an city, typical hydrological years were divided into different hydrographic periods. Then, water environmental capacity was analyzed. The calculating results showed that improving water quality of Jinxi River was based on controlling ammonia nitrogen's total amount from upland water. In dry season and normal season, the total amount of ammonia nitrogen,which were whittled at least 19.84 kg·d^-1 and 36.50 kg·d^-1 that can meet water functional requirements, respectively. Meanwhile, coastal sewage interception strength and standard-reaching rate of point source emission should be improved.3) Experiments of artificial simulated rainfall were conducted in Jinxi River Jincheng segment. Three kinds of rainfall intensities were designed in experiments to analyze effects of four types of land using in runoff and sewage yield. The results showed that for the same land using types, with in rainfall intensity increasing, the concentration of the first flush and average concentration were increase in overall. Under the same rainfall intensity, different land using types were compared. For the concentration of TN and TP, woodland, farmland and grassland were higher than road. And for COD, each land using types had little difference. Only under heavy rainfall intensity, road was higher than the other three land using types. From the view of pollutant content, the process of main pollutant yield was nitrogen.4) The UPLRs calculations of different land using types showed that, in addition to NH3-N, UPLRs of road were the highest, which values of TN, TP and COD reached 53.38 kg·hm^-2·a^-1,9.19 kg·hm^-2·a^-1,745.53 kg·hm^-2·a^-1, respectively. UPLRs of NH3-N was the highest in farmland, which values of TN, TP and COD reached 43.81 kg·hm^-2·a^-1,8.80 kg·hm^-2·a^-1,500.55 kg·hm^-2·a^-1, respectively, next to road. UPLRs of grassland were the minimun, which values of TN, NH3-N, TP and COD were 30.28 kg·hm^-2·a^-1,13.62 kg·hm^-2·a^-1,5.49 kg·hm^-2·a^-1, 213.65 kg·hm^-2·a^-1, respectively. Conclusively, the order of UPLRs were road>farmland>woodland>grassland.