Research On Estimation And Allocation Of Total Phosphorus TMDL In Wuxi Reach, Daning River

Total amount control of water pollutants is one of the most important measures to protect and improve the water environmental quality in China. Now, control of water pollutants in our country undergos the stages of concentration control and goal capacity total amount control, which exist many disadvantages and are not in accordance with the water environmental capacity. Thus, the system of capacity total amount control should be established in the watershed scale with the innovation and breakthrough in theory and technology of total amount control. This is of signality to the work of pollution control.Owing to the change of flow condition and the back flow in the aera of the Three Georges Reservior, the back water reach of Daning river is eutrophic in recent years. In this study, the upper basin of Daning river, controled by Wuxi hydrologic station, is selected as target area. The duration curve method which is included in the toolbox of TMDL program established by USEPA is applied to estimate TP TMDL. The calculation formula of TMDL is used to initially allocate TP load to pollution sources. The SWAT model is run to analyse the characteristics of the pollution load distribution in the watershed, and the results of the model serve to the allocation of TP load. The main conclusions of this thesis are as follows.(1) In Spring and Winter, the TMDL of the water body is 82.68kg/day and is 255.14kg/day in Summer and Autumn. Total amount control of water pollutants should be preferentially implemented in Summer and Autumn.(2) TP load of agricultral land is more than 50% of the total load in the watershed, more than the loads of forest and pasture land. The key area where total amount control should be preferentially implemented is agricultral land.(3) The allowable TP load of point source is 9.74kg/day, which is 3.43% of the total load. It is no need to reduce TP load of point source.(4) The allowable TP load of non-point source varies from flow. In Summer or Autumn, the elimination of TP load on agricultral land is 78.04 kg/day, which is allocated to sub-basins according to the contribution rates based on the ruesults of SWAT model.(5) TP load should be mainly controlled in Sub-basin 7, which is located in upper basin of Dongxi river.