Study On Rainfall Runoff Pollution In Yuehe River Basin Of Hanyin County Based On GIS And SWMM

At present,the environmental quality of surface water in China has been improved,but the overall situation is still not optimistic,especially the pollution of rainfall runoff has become one of the important reasons for the deterioration of water quality in the basin.Yuehe River in Hanyin County is an important tributary of Hanjiang River.Controlling rainfall runoff pollution is very important to ensure that“a river of clear water flows northward forever”.This paper takes the Yuehe River Basin in Hanyin County as the research area,and constructs the SWMM model of rainfall runoff pollution quickly with the support of GIS and RS technology,in order to analyze the variation characteristics of rainfall runoff pollution in the basin and quantify the reduction effect of rainfall runoff pollution control measures.The main research results are as follows:(1)Based on the DEM grid,the hydrological analysis was carried out with the support of GIS technology,and the boundary range and river network system of Yuehe River Basin in Hanyin County were extracted,and 41 sub-watershed were automatically divided.Based on the Landsat-8 remote sensing image grid,the study area is supervised and classified with the support of RS technology,and the coverage information of underlying surface land use type was interpreted.(2)The extracted natural sub-watershed and river network water system are generalized into the spatial structure of the model,and the basic information of the watershed is obtained by using GIS and RS technology to complete the construction of the watershed SWMM model.After the adjustment of the model parameters,the actual runoff coefficient of the underlying surface and the historical peak discharge of the urban river reach are used to verify the model parameters.The error of the verification results is less than 12%in each rainfall recurrence interval.The results show that the SWMM runoff pollution model based on GIS and RS technology also has high accuracy in natural watersheds which lack data.(3)Using the simulation results of the SWMM model,the variation characteristics of runoff and water quality on the scale of river channel and subcatchment under single rainfall are analyzed.At the river channel scale,after the intersection of Donghe river and Yuehe river,the peak discharge of the river is doubled.Under 50a rainfall recurrence interval,the peak discharge of the R40 reach which flows through of Shuangru Town reaches 3077.153 m~3/s.The residential areas on both sides of Yuehe River in Jianchi Town,Puxi Town and Shuangru Town are prone to floods.The middle reaches of Yuehe River flow through the county area with high pollutant concentration,the maximum COD,TN and TP concentration in the R19reaches is 31.41 mg/L,8.48 mg/L and 1.71 mg/L respectively under 1a rainfall recurrence interval.At the subcatchment scale,the catchment area with the highest runoff depth and COD,TN,TP scour load is located in Yuehe River channel area.The underlying surface with the largest rainfall runoff pollutant load is residential zone,followed by cultivated land.(4)According to the spatial distribution characteristics of rainfall runoff pollution in the study area,the combined LID measures of sunken green land and permeable pavement are set up for the residential zone in the basin,the total amount of COD,TN and TP erosion of single rainfall under 1a rainfall recurrence interval decreased by 5.36%,5.93%and 7.13%respectively.Combined measures of returning cropland to forest and balanced fertilization for cultivated land in the basin,the total amount of COD,TN,TP erosion of single rainfall under1a rainfall recurrence interval decreased by 2.03%,10.37% and 7.20% respectively.