Analysis Of Seawater Intrusion Characteristics And Tendency In The Chongming Island

Seawater Intrusion is that seawater or saltwater intrude into the continent along the aquifer. Under the effects of the natural and artificial factors, the hydrodynamic condi tions of aquifer in the coastal area has been changed, which break the equilibrium between the seawater and the freshwater, hence the salt-fresh interface moves on the continent. Chongming Island is located in the mouth of the Yangtze River. It’s ocean currents and waves coupled with irrational exploitation of groundwater which makes the seawater intrusion disaster in the region getting worse.This paper based on the two stages periodic data from field survey from August2009to July2010and July2011to May2012, analyzed the distribution of Chloride concentration and mineraliza tion, then basicly got the distribution and dynamic change trend of the high-salt-water in Chongming island.The actuality assessment indexes are conceived through choosing the factors of concentration of Cl-and mineraliza tion. Spatial analysis of ArcGIS software is applied involving in the evaluation process expressing. The result shows that the area of seawater intrusion in Chongming is primarily planar invasion and the width of seawater intrusion is about3-5km. The seawater intrusion area which mainly distributed along the morth region is more than one-third of Chongming island.The geographical location of Chongming island is very special that quaternary strata is quite single. Through a comprehensive analysis of the factors that affect seawater intrusion in Chongming island, we found that:Increased precipitation makes Chongming Island groundwater get recharged, therefore weaken the impact of seawater intrusion; Increased precipitation can also increase the runoff of Yangtze River which furnish a lot of freshwater to make sure the south region in Chongming to get little influence of seawater intrusion. Seawater intrusion along the north region of Chongming island develop rapaidly around climax, tide, storm surges and dry season. By comparing the monitoring data of the first second stage, we found that:The seawater intrusion disaster in Chongming island will increase in the future no matter in the area or severity; The north part of the island will be long-term impacted by seawater intrusion, wich may possibly become highly or serious invasion in the second half of eveay year.Based on the comprehensive field survey, this paper analyzes the conditions and the degree of the risk, evaluates and forecasts trend of the seawater intrusion in the region which provide technical support for forecasting and prevention of seawater intrusion in Chongming island.