Groundwater Vulnerability Assessment Based On Process Simulation

Luyi County,Henan Province,is a large inland agricultural county.Groundwater is an important water source in the region.With the growth of economy and population,the groundwater environment in the region is facing great pressure.Groundwater vulnerability assessment can reflect the risk degree of groundwater system pollution,and provide a theoretical basis for the management and protection of groundwater resources in Luyi County.Based on the field hydrogeological survey,this paper analyzes the actual situation of the study area,constructs the DRAIC-LN model,and evaluates the groundwater vulnerability of Luyi County.According to the natural breakpoint classification method,the study area is divided into five levels(higher vulnerability area,high vulnerability area,medium vulnerability area,low vulnerability area and lower vulnerability area).The results show that the groundwater vulnerability in the study area is basically in the medium level,The areas with high groundwater vulnerability are mainly distributed around Qiuji Township,Luyi County and Jiatan town.In order to further characterize the temporal and spatial distribution of nitrate in the groundwater system,a combined model of unsaturated zone and saturated zone was established by using HYDRUS-1D and Visual MODFLOW software.The leaching amount of nitrate obtained from the simulation of unsaturated zone process was taken as the input of concentration recharge of saturated zone solute model,The change trend of nitrate in the next 10 years is predicted.According to the groundwater quality evaluation standard,the nitrate pollution scope in the simulation period is divided into five grades(higher vulnerability area,high vulnerability area,medium vulnerability area,low vulnerability area and lower vulnerability area).From the simulation results,it can be seen that the areas with high groundwater vulnerability are mainly distributed in Qiuji Township and Zhaocun Township,It is scattered around the north of Yanghukou and Jiatan town,Luyi County.The results of overlay index method(DRAIC-LN model)and process simulation method are basically consistent.The areas with high groundwater vulnerability are mainly distributed in the vicinity of Qiuji Township and Zhaocun Township,and in the vicinity of Jiatan Town,Xuanwu Town,Yanghukou town and Luyi County.Therefore,it is suggested that the relevant departments should strengthen the protection of groundwater pollution in this area.