Water Quality Simulation Based On WASP Model And Attribution Analysis In Daihai

Understanding the temporal and spatial distribution characteristics of water quantity and quality,as well as the simulation and attribution analysis of pollutants is of great significance for the governance and restoration of the Daihai environment.Based on the continuous monitoring data of water quality and water quantity in Daihai from 2005 to 2021,this study uses Statistical analysis and Kriging interpolation methods to analyze the temporal and spatial distribution characteristics of dissolved oxygen（DO）,potassium permanganate index(COD_Mn),total nitrogen（TN）,total phosphorus（TP）,and water volume（V）,and applies Water Quality Analysis Simulation Program model to simulate and verify pollutants,and then the correlation analysis and multiple linear regression analysis were used to quantitatively study the impact of climate change and human activities on the water environment,revealing the temporal and spatial distribution of pollutants in the Daihai,and proving the main influencing factors of the water environment.The main research conclusions are as follows:（1）From 2005 to 2021,the concentrations of COD_Mn,TN and TP in Daihai showed an upward trend year-on-year.In 2021,compared with 2005,it has increased by 58.8%,222.4%and 11.4%respectively,and it has always been in the range of ClassⅤwater.The concentrations of DO showed a trend of first decreasing and then increasing,and was stable in the category III water range;the lake water volume decreased year by year,and in 2021（0.93 billion m~3）was only 14.9%of that in 2005（625 million m~3）.During the year,the concentrations of DO,COD_Mn,TN and TP showed a fluctuating upward trend,with certain seasonal changes.（2）The spatial distribution characteristics of pollutant concentrations in the Daihai are generally higher in the east than in the west,with relatively high pollutant concentrations near the lake entrance and low in the lake center area.The total nitrogen concentration in the year showed a trend of shifting from west to east,the potassium permanganate index showed a trend of shifting from the northeast to the southwest,and other pollutants did not change significantly.（3）Based on the measured data from 2019 to 2021,the WASP model was used to simulate DO,COD_Mn,TN and TP.Through parameter calibration,sensitivity analysis,simulation and verification,the results show that the WASP water quality model has good applicability in the Daihai.The relative error between the simulated value and the measured value during the simulation period is within±10%.During the verification period,the relative error between the simulated value and the measured value accounted for 95.8%within the range of±40%.Among them,the TN simulation result was better,with a relative error and RMSE of 6%and 0.21,respectively;the DO simulation result was relatively poor,and the relative error and RMSE were 20%and2.29,respectively.（4）From 2005 to 2021,the environmental change of the Daihai was affected by both climate change and human activities.The V,TN and DO were most affected by the tertiary industry,population and GDP,respectively,all showing extremely significant negative correlations（R=-0.910,P≤0.01;R=-0.836,P≤0.01;R=-0.826,P≤0.01）,and the COD_Mn and TP were most affected by the primary industry and GDP per capita,respectively,and both showed a significant positive correlation（R=0.495,P≤0.05;R=0.485,P≤0.05）.The temperature,humidity,and rainfall in the Daihai Basin changed by 0.07°C,0.28%and 12.52 mm before and after rainfall,which had little impact on the water environment.However,the evaporation is more than 2 times higher than precipitation all year round,and the development of secondary and tertiary industries has accelerated the reduction of water resources and aggravated the pollution of the water environment.The reasonable allocation of water resources,the control of pollution sources,and ecological water replenishment are conducive to the restoration of the Daihai environment.