Research On Seawater Intrusion And Prevention And Remediation Measures Of Dalian City

Based on summarizing the concept of seawater intrusion in worldwide scale, the author defines the seawater intrusion in relatively comprehensive way as the following: under the effect of natural and artificial factors, the hydrodynamic condition of the aquifer in the coastal area has been changed, which, causes the equilibrium between the freshwater and seawater, hence the seawater that contacts the freshwater hydraulically intrudes into the continent along the aquifer, and the salt-fresh interface moves towards the continent, as a result the freshwater resources are contaminated.The basic characteristics, distributing area, process, trend, cause of formation and harm of seawater intrusion in Dalian City are analyzed detailedly. The analysis shows that there are three types of seawater intrusion in Dalian City: area-form intrusion, linear-form intrusion and cavity-shape intrusion. The trend of seawater is that the intrusion area varies as following rule: small to big to small to big, and the causation of seawater intrusion is the appropriate hydrodynamic and hydrogeological condition, and the main reason is that human activities change the groundwater hydrodynamical condition. The seawater intrusion does great harms to the industry, agriculture and people's living conditions, also it restricts the development of economy of Dalian City.In Gangjingzi district, the typical area, the calculation model of allowable groundwater exploitation is built by the method of artificial neural network. In the model, two input units are corresponding to the allowable withdrawal and precipitation, and seven middle connotative units and two output units are corresponding to the concentration of Cl- and the area of seawater intrusion in Gangjingzi. The calculation results are: 30 million m3/a for allowable withdrawal. As long as the practical withdrawal is kept below the allowable withdrawal, the seawater intrusion can be prevented effectively.According to the geological and hydrogeological condition and the status of groundwater utilization, the policy of preventing seawater intrusion and realizing the favorable running of groundwater system which is that reducing the exploitation on groundwater resources, increasing the recharge to the ground freshwater to drive up the groundwater level, building the water conservancy to increase source .save runoff and block the seawater intrusion, carrying out the ecology-improving measures, enhancing the consciousness of saving water and management of water resource.