Simulation Of River Rater Quality In Pingxiang City And Its Response To The Construction Of Sponge City

Pingxiang city was selected as one of the first 16 sponge city construction pilot cities in China in 2015.The main part of reconstruction in its demonstration area is the old town of Wanlongwan in Anyuan district.The water quality of Wufeng river in the demonstration area plays a symbolic role in the regional water quality.This paper studies the river water quality of Wufeng river,reveals the response rule of river water quality to different rainfall intensity and underlying surface,and puts forward the prevention and control measures of water pollution in the construction of sponge city,which is of certain practical significance to regional water environment management and sustainable development.Aiming at the pollution problem of Pingxiang sponge city demonstration area,this paper analyzes and evaluates the water quality of the studied reach by time series and stages through collecting and sorting the information of the study area and adjacent hydrologic stations,river section and urban underlying surface,sponge construction project information and water quality of typical sections in recent years.Based on the collected data,a MIKE11 hydrodynamic and water quality coupling model was established,and the model was calibrated and verified according to the measured data.When the model was applicable,scenario simulation was carried out for different underlying surfaces and different rain intensity,and the influence of sponge city construction on river water quality is analyzed.This paper draws the following conclusions:(1)According to the water quality evaluation analysis of the inlet section and the outlet section of the Wufeng river reach studied,during the high construction speed and intensity of sponge city,the water quality was significantly affected,and the concentration of pollutants in the outlet section increased significantly.Ammonia nitrogen was the most important pollution factor,followed by total phosphorus.Water quality was basically restored to the pre-construction period after the sponge city reconstruction and construction was basically completed,concentration of organic pollution indexe such as DO,CODMn,CODCr,BOD5 is slightly higher than a previous day,but basicly has returned to the water quality protection measures such as target ? class level.Compared with the pre-construction period,ammonia nitrogen and total phosphorus were somewhat relieved,suggests that sponge city construction play a protective role on water quality.(2)MIKE11 Hydrodynamic module and Advection-Dispersion module were selected to establish the river water quality model of Pingxiang sponge city demonstration area and verified.The simulation value and the measured value can be compared and analyzed to confirm the good fitting of the model.In the hydrodynamic module,the bed roughness of the reach studied was 0.030 and the Nash-Suttcliffe efficiency coefficient was 0.9789.In the water quality module,the diffusion coefficient is 5~8m3/s,the attenuation coefficient of ammonia nitrogen is 0.07/d,and the attenuation coefficient of total phosphorus is 0.03/d,basically reflecting the change process of river water quality,which can be applied to scenario simulation.(3)In the simulation and prediction of water quality,the change process of water quality in the river course has completely different performance to the underlying surface before and after the sponge transformation,and the modified underlying surface conditions have played an effective role in reducing the pollutants in the river course water body.During the process of water quality change,the pollutant concentration was significantly reduced after interception and purification by the sponge,and the peak value was earlier,and the target water quality protection category could be reached faster.