Recognition And Simulation On Agricultural Non-point Source Pollution In The Drainage Basin Of Dahuofang Reservoir

Dahuofang Reservoir is the drinking water source for 23 million people in major cities in central and southern Liaoning Province.Current research shows that agricultural non-point source pollution in the drainage basin of Dahuofang Reservoir has become one of the important sources of water pollution.This study analyzed conventional water quality indicators in surface water to assess water quality and identify factors of water pollution.In addition,we used numerical simulation to identify atrazine residue in groundwater and its impact on surface water.In order to assess water quality and identify factors of water pollution in the basin of the Dahuofang Reservoir,we analyzed the water quality data of the basin from 2014 to 2018 using the comprehensive weighted average nutritional status index and principal component analysis methods.Results showed that the major water pollution factors in the basin were total nitrogen(TN)and fecal coliform(FC).Water in the reservoir had the middle nutrient level,limited by phosphorus,and the eutrophication index gradually decreased over years.The sources of water pollution in the basin were primarily agricultural cultivation(for total nitrogen),and rural activities and livestock breeding(for fecal coliform).The contribution of agricultural cultivation as a source initially increased and sequentially decreased over the years.The contribution of rural activities and livestock breeding remained constant over the years.Therefore,the heavy pollution of total nitrogen in the waters of the basin was attributed to both the continuous emission from agricultural activities and the poor utilization of total nitrogen in waters with a lack of phosphorous.In order to identify the impact of farmland residual pesticides on groundwater and surface water,we analyzed the structural characteristics of groundwater aquifer in Dahuofang Reservoir,used FEFLOW groundwater simulation software to establish groundwater flow mode.We compared the simulated groundwater flow field with the actual monitoring data and found that: The error between the simulated value of groundwater level and the observed value does not exceed 1 m.The model can accurately simulate the groundwater environment in the drainage basin of Dahuofang Reservoir,which is representative.We established a solute transport model based on the groundwater flow model.Results showed that Atrazine accumulated in the aquifer for a long time,affecting the safety of groundwater.At the same time,Atrazine in the groundwater system migrated to surface water,polluting the Dahuofang Reservoir and the three rivers.In general,agricultural non-point source pollution has become one of the main sources of surface water pollution in the drainage basin of Dahuofang Reservoir.Atrazine remained in farmland could pollute groundwater and surface water.The results of this study provide a scientific basis and model basis for monitoring and protecting the water quality of the drainage basin of Dahuofang Reservoir.