Water quality safety prediction model for drinking water source areas in Three Gorges Reservoir and its application

摘要

In recent years, water pollution accidents have become major ecological environmental pollution ones in China, and bring potential risk to urban drinking water safety. The research aimed to develop a water quality safety prediction model for drinking water source areas in Three Gorges Reservoir and simulate pollutant distribution in water bodies under pollution accident conditions. In this study, a new algorithm of two-dimensional water quantity model was proposed, which incorporated Digital Elevation Model as a computational grid into the Geographic Information System. By comparing the water quality observed values with the predicted values of the study area in 2014, the relative error was less than 6%, the model can be applied in a reasonable range. Furthermore, this study assumed a pollution accident that the Huangjuedu drinking water source area was polluted by TP pollution (level V) of 0.4 mg/L. Based on the statistical annual date of Zhutuo hydrological station in 2016 (as blank group), dispatching test that was conducted by increasing discharge flow of Xiangjia Dam Reservoir. The results shows that the water velocity of intake increased with discharge flow of Xiangjia Dam Reservoir, and that the maximum water velocity was 2.051 m/s. The pollutant concentration of HDWSA intake decreased rapidly with the increase of the discharge flow. When the discharge flow was 0m(3)/s, the concentration of intake reached the level III water quality standard after 127.8 min. When the discharge flow was 12,000 m(3)/s, the concentration of intake reached the level III water quality standard after 116.7 min. In the dispatching test, the rate of migration and diffusion of the pollutant to the lower reaches was greatly affected by the discharge flow of Xiangjia Dam Reservoir. The model could predict the water velocity and pollutant concentrations at the intake, as well as temporal-spatial distributions of pollutants in the whole water source area. Prediction results of the model were helpful for management departments to predict grasp the change of pollutions timely and accurately, and make corresponding plans under accident conditions.