Hydrochemical indexes of seawater intrusion and comprehensive judgement on intrusive degree

The paper discusses the use of five hydrochemical indexes in evaluating seawater intrusion, and ranking the intrusion degree for Cl -, M, Br -, rHCO 3/rCl and SAR. The fuzzy mathematical comprehensive judgement model has been adopted as the method of adjustment. Based on more than 300 water samples obtained from four typical profiles in the coastal region of Laizhou Gulf during the period from June 1993 to June 1995, we made a comprehensive judgement of seawater intrusion degree. The result shows that intrusion degree was becoming heavier from June 1993 to June 1994, but more steady and inactive in the high level of intrusion degree in the perennial severe intrusion zone from December 1994 to June 1995. Since entering the 1990s up to now, the process of seawater intrusion has translated from its peak developmental stage from the 1970s to the 1980s into a stage of equilibrium and slow development mainly because the intruded area expanded inland, precipitation increased at some extent recently and various measures of prevention and harness begin to show the effect.