Dalian City Zhoushuizi Seawater Intrusion In

Seawater intruding into groundwater layer caused by the drop of freshwater level of earth is a worsening phenomenon of environmental geology named seawater intrusion. It is an artificial disaster of nature induced by human's social activities in coastal cities. The long-term co-operation of many environmental factors of nature and society has resulted in seawater intrusion, and the most direct causes are sustained lowering of groundwater level and severe deficiency of rainfall. Recently, most of coastal cities in China have been up against seawater intrusion problem to some extend. This problem in the city of Dalian is relatively serious, and even affects the national economy and the people's livelihood. It has become the leading question for the development and utilization of groundwater.The situation of seawater intrusion in the district of ZhouShuizi Dalian is simulated applying SUTRA in this paper. The software TECPLOT which shows a powerful function in technological drawing, is used to do post processing analysis towards the simulation results. About the technique and method to controlling seawater intrusion disasters inland and abroad, some control measures such as setting up a freshwater barrier and adding a cutoff wall are discussed, combining with the specific fact in China.In chapter 1, disasters brought by seawater intrusion to many countries, especially China, are discussed at first, the background and significance of project selection are analyzed, too. Then, on the basis of this, general conditions, mechanism, basic theory of seawater intrution, research methods and present conditions on seawater intrusion inland and abroad are summarized. Finally, the contents and approach for this research are put forward.Chapter 2 is the basis of this paper and hydrogeological conditions of the research region are revealed here. Fundamental principle of SUTRA numerical model and TECPLOT graphical post processing software are introduced in Chapter 3.The model is applied to the district between Dalian Bay and ZhouShuizi in Chapter 4. Based on relevant geological data by Bureau of Hydrology, general geological condition of the research region is analyzed, and a conceptual model is established. The situation of seawater intrusion into inland area during three years is simulated and compared with the observated data. Results show that the model is reliable, and the prediction is reasonable. So it can be used to make project planning for utilization and exploitation of groundwater resources. In addition, the variation tendency of intrusion distance along with precipitation amount and the variation law of the width of transition zone and seawater-freshwater interface are analyzed, providing some references for establishing control measures subsequently.In chapter 5, several sorts of back pour-extracting schemes are supposed and the variation law of 250mg/L,5g/L,10g/L concentration contours are analysed quantificationally to illustrate the function of freshwater barrier. During the forming process of freshwater barrier, back pour amount is the key factor. The higher the amount is, the more remarkable the function is.Then, optimum selection of the back pour plots and the variation situation of seawater-freshwater interface are explained by designing projects. Theshielding effect of cutoff wall to seawater intrution is analysed and demonstrated in Chapter 6. Finally, conclusions and research tendency are summarized briefly.