山东龙口-莱州地区的海水入侵

THE PATTERN OF SEAWATER INTRUSION IN THE LONGKOU-LAIZHOU AREA

大面积海水入侵(83.7—238.3km^2,占平原区总面积的18.6％—31.5％),宽1.5—6.0km过渡带的存在以及海水入侵区与地下水水位大幅度下降所形成的低于海平面的地区在分布上相互关联,是本区海水入侵的主要特点。阳离子交换则在海水入侵区地下水化学成分形成过程中起着重要作用。

The present situation and features of the seawater intrusion (or encroachment), the hydrochemical characteristics of groundwater, the features of saline water-fresh water interface and its movement in the Longkou-Laizhou area, Shandong Province, are studied. In 1989, the area of seawater intrusion is 238.3 km^2 in Laizhou (31.5% of its total plain area) and 83.7km^2 in Longkou (18.6% of its total plain area) respectively. The seawater intrusion developed from a point to a large scale. Restricted by geological conditions, the forms of seawater intrusion are variable. The velocity of seawater intrusion varied from place to place. There are close connections between the area of seawater intrusion and the area whose groundwater level is below the sea level due to overpumping. The real distribution of seawater intrusion is connected with the area where strong, intensive pumping exists. The existence of lagoonal or marine argillaceous sediments in coastal zones accelerated the enrichment of Cl^- in groundwater. In seawater intrusion areas there is a broad transition zone with a width of 1.5—6.0 km between saline and fresh water. The groundwater in the transition zone is by no means a simple mixture of fresh water and saline water. The cation-exchange played an important role, which caused the decrease of Na^+ and the concentration of Ca^(2+) in the transition zone. There exist two types of saline waterfresh water interface which is related to the pomp discharge and the distribution of pumping wells. The interface formed at the continental side nor far from the area where strong, intensive pumping is carried out, and the seawater intrusion stopped there. Finally, this paper discusses the causes of the seawater intrusion and effective measures to prevent and control seawater intrusion.