Analysis Of Pollution Sources In Duihekou Reservoir Basin In Zhejiang Province Based On ReNuMa Model

A good water environment is the basis of human survival and development.Water quality evaluation and pollution source analysis are the key to protecting the environment,so they are hot spots in related fields.The Duihekou reservoir in Zhejiang Province is the drinking water source of Deqing County,in recent years,the drinking water quality of the reservoir faces serious threat due to the increase of agricultural land and development of tourism.Therefore,it is particularly important to has a grasp of the water environment conditions in the reservoir basin and find out the main pollutants.Taking the Duihekou reservoir basin in Zhejiang Province as the research area,based on the theories of physical geography,basin water environment and mathematical statistics,the water quality of rivers are sampled in the field and tested.This paper analyzes the temporal change and spatial difference of various water quality indexes of rivers in the basin by using multivariate mathematical statistics method.Single factor evaluation method and comprehensive pollution index method are used to evaluate the water quality of river sections in the basin.Meteorological,hydrological and water quality,land use,pollution sources and other data are combined to construct ReNuMa hydrological and water quality model in the study area,analyzing the pollutant load in the basin,the source of pollutants,and putting forward corresponding prevention and control measures and suggestions.The main research contents and conclusions are as follows:（1）The temporal and spatial variation of river water quality in the study area is obvious.In terms of time,the water quality indexes fluctuate greatly in each month of the year.The values of DO、TN and p H indexes in flood season are lower than those in non flood season,and TP、NH₄⁺-N、CODMn and Chl.a,the index value in flood season is higher than that in non flood season,and the water quality index SS has no obvious law in time difference;Spatially,the water quality of huangfenwu is the worst,the water quality of Shiyi is poor,the water quality of Panxi is general,and the water quality of other rivers is better.（2）The water quality results based on the single factor evaluation method are poor,and the single factor water quality evaluation results of 86%of water samples are between class IV standard and inferior class V standard.The water quality results based on the comprehensive pollution index evaluation method are good,and the water quality evaluation results are mainly"light pollution".TN is the main pollution factor of surface water environment,followed by TP.（3）The simulation results of renuma model are illustrated:from 2016 to 2020,the nitrogen and phosphorus load in the basin showed a fluctuating trend of first decreasing,then increasing and then decreasing.The sub basin with the highest nitrogen and phosphorus load in the study area is Shuangxi basin,with nitrogen load up to 62.34t/a and phosphorus load up to 3.76t/a.The sub basin with the lowest nitrogen and phosphorus load is Donglingwu basin,with nitrogen load only 0.87t/a and phosphorus load only 0.05t/a.Compared with other basin,Huangfenwu basin,Shiyishui basin,Lakeside area and Shuangxi basin have more nitrogen and phosphorus load per unit area and more serious water pollution.（4）The nitrogen and phosphorus pollution sources in the study area are mainly non-point source pollution,followed by domestic pollution sources.Paddy field and tea garden are the main contributing areas of nitrogen and phosphorus pollution in non-point source pollution,accounting for 77%of the contribution rate of nitrogen and phosphorus pollution.The fertilizer widely applied in agricultural land is the main source of nitrogen and phosphorus pollution in surface runoff in the study area.