Simulation of water transferring impact on the water quality in Danjiangkou reservoir of the South to North Water diversion middle line project

Danjiangkou reservoir supplies the water source for the South-to-North Water Diversion middle line project, the entire planning area plays an important role in public ecological responsibility, and the state proposed strict requirements of indicators of water quality and quantity, which means the security of overall water environment is the basic phase of achieving water diversion objectives. Based on the analysis of water pollution sources and current situation of the reservoir, this paper chooses 2010 and 2030 as target years to evaluate the objective, adopts Dillon model to build the relationship between eutrophication and phosphorus load, realizing macro-simulation of the eutrophication trend of Danjiangkou reservoir. The result shows that the risk of eutrophication does exist for the reservoir, which needs water environment capacity accounting. Considering current situation and pollution features of the water quality in Danjiangkou reservoir, and national integrated planning requirements of water resources, we choose COD and NH3-N as control indexes of calculating water environment capacity, and two-dimensional water quality model for rivers, to carry out simulation analysis of water environment capacity changes of local polluted area in the reservoir. The results show that when the water level of the reservoir is increased to 170 m, the total dissolved COD and NH3-N of regional water bodies within a month decreased compared to what it is at the water level of 157 m, local water environment capacity is also weakened, which the state government and reservoir departments should give attention to.