| Saline water encroachment area can be divided into apparent encroachment and dormant encroachment. The first one is the spread of saline water towards freshwater in nature state, and the second is the fast spread of saline water towards freshwater because of human active work. As one of the typical environment disaster in the south plain of Laizhou Bay, the &%. occurrence of saline water encroachment has close relation with modern environment and ancient environmental evolution. The sediment environmental transformation is the setting factor of saline water encroachment, and the modern environmental change is the spring factor. By analysis the environmental change in the area of Weihe River downstream hi the Laizhou Bay southern Plain, this thesis studies the formation and change of saline water encroachment in the angle of environmental science and sedimentology.By many field reviews and validations in this study, a great number of terra drill data are collected. In the studied area, selecting the typical section, and drilling the bore core sample. Doing the granularity analysis, the sporopollen analysis, microfossil analysis, ' C and TL (thermoluminescence) age measurement. By the hydrochemical surveillance to the typical section, detailed data of the underground water movement regulation in the transition area of saline water and freshwater are obtained.By the analysis of many sedimentology indexes, the paper does the systematical study on the environment evolution in Weihe River downstream. It also renews and rebuilds the sediment sequence of region paleoenvironment. By contrasting with border area, there are many proper evolution characters under global environment change. Under the differential subsidence tectogenesis control in the Quaternary, the sediment in the area can reach 300 meters in depth, which mainly are coarse sand, medium sand and silt. Because of the Quaternary ice age climate change, there are three times sea level rise fluctuation and sea-triphibian vicissitude since Epipleistocene in the plain, and the sediment environment is the pratum plain and the littoral or shallow water region alternating. Paralic sediments are formed with advance and retreat of beach line, and the continental facies are mainly paleochanle sandy sediment, the grain of whose sediments diminish with the sediment, and there are thick douke aquicludes in it. With the rise of sea level, greatness sea shore PlainIVwas submerged, and the resorted seawater became bittern water by evaporation and concentration. The dry and cold climate after the drop back of sea level is propitious to the evaporation and concentration of bitter water, which seeps down through permeable beds. After the dropping of sea level, the bare Bohai Sea floor becomes the mainly resource of the sediment in south shore of Bohai Sea, which forms the loess sediment in the Late Epipleistocene stratum and is definite permeability barrier to saline water encroachment.With the environmental evolution since the Epipleistocene, the sediment substances of bitter water and paleochanle are formed, which have close water conservancy relation. The bitter water can be divided into phreatic flow bitter water and bearing bitter water by its embedding, and the later is the main resource of saline water encroachment, which has high concentration, abundant reservation and vast distribution. The paleochanles are the main channels of saline water encroachment, the diversity of whose sediment has big influence on the fashion and velocity of saline water encroachment. This paper illustrates the relation of stratum sediment and saline water encroachment, by analyzing the difference of paleochanle sediment and using the ground water hydrochemical data.The recent changing environment factors based on the paleoenvironmental evolution, such as climate and precipitation, groundwater level, and the exploration of groundwater are the driving factors of saline water encroachment, whose change directly influence its velocity.By analyzing the change of paleoenvironme...
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