Trend Simulation And Characteristic Analysis Of Sea(Salt) Water Intrusion In Weifang City

The artificial overexploitation of groundwater in coastal area results in a great decrease of groundwater level and the destruction of hydrodynamic balance between seawater and fresh water,which leads to the movement of salty and fresh water in the direction of land,that is,the intrusion of sea water.Saltwater intrusion refers to brine or saltwater bodies buried in sea facies sediments formed by Quaternary transgression,which push the saltwater-freshwater interface inland due to excessive exploitation of its adjacent freshwater resources.Saline water intrusion is a common problem of groundwater environment in the coastal plains of the world.This paper takes Shouguang,Hanting and Changyi in the northern part of Weifang City as the research area,mainly conducting the following research:(1)To analyze the influence factors of water intrusion in the sea(salty)of each administrative region,including the super-mining of the groundwater,the hydrogeologic conditions,the precipitation,etc.(2)A numerical simulation model was established by using SEAWAT Module in MODFLOW to simulate the trend of seawater intrusion and analyze the simulation results.The main research results are as follows:(1)The change trend of the area of sea(salty)water intrusion in the study area is consistent with that of the area of the negative value of groundwater level,both of which show a gradually increasing trend,and the correlation coefficient reaches above 0.9,indicating that the area of the negative value of groundwater level is closely related to the area of sea(salty)water intrusion.(2)According to the analysis of hydrogeological conditions,the sea(salty)water intrusion in shouguang city was planar intrusion along the distribution area of quaternary sediments in the early stage.Since 2002,the salt-water boundary began to advance to the location of the ancient river channel,and the salt-water invasion front line showed the distribution characteristics along the ancient river channel.The cold kiosks were mainly planar intrusions along the quaternary sediment distribution area,while the changyi was mainly finger-like intrusions along the shallow buried ancient river channel.(3)In the interior of the study area,only the northern part of Jiaolai River has modern seawater intrusion.In the 9-eye monitoring wells,the Cl~-concentration in the monitoring wells close to the river is obviously higher,reaching a maximum of 727 mg/L;When the vertical distance from the north of Jiaolai River was 2.8 km,the Cl~-concentration was the lowest,265mg/L.It shows that the scope of seawater intrusion affecting both sides of the river is limited in the course of upstream,and the influence range is about 3 km.(4)In the program prediction,three scenarios are set up to predict the implementation effect of each program under the condition of flat water year.By contrast,Scheme 1 should be the first choice for long-term treatment of salt water intrusion in the study area,and Option2 can be used as an effective supplement to control saltwater intrusion.In this paper,the trend simulation and characteristics analysis of sea(saline)water intrusion in the study area are carried out.The corresponding research results can provide the basis for local government departments to solve the problem of sea(saline)water intrusion.