Research On The Change Of Groundwater Quality And The Interface Of Salt And Fresh Water In The Representative Area Of North China Plain

The surface water resources are deficient in the middle and eastern plain of North China, and most of shallow groundwater is salty water distributed from west to east with a wedgy shape.Thus, deep fresh groundwater underlying salty water body becomes the main water supply resources in this region. Over the past 30 years, along with the rapid development of economy and the raise of living standard, deep groundwater has been overexploited continuously. So, it has threatened the security of supply water seriously through deep groundwater salinization and the interface of salt and fresh water downgoing. Therefore , the thorough research on the change of groundwater water quality and the interface of salt and fresh is urgently needed at present.With Hengshui City in the middle plain of North China Plain as the representative research area, this paper, based on the system analysis of the dynamical evolvement of groundwater and the analysis on data of groundwater hydrochemistry and well log, has revealed change characteristic of groundwater quality and the interface of salt and fresh water downgoing in this area, has forecast the change of groundwater quality and the interface of salt and fresh water downgoing in the representative research area, and has put forwards rationalization proposals for groundwater exploitation as well .For the study, lots of basic data concerning the physical geography, geology, hydrogeology, groundwater mining use, water quality and so on have been collected. Furthermore, log information of more than 2700 deep bore-holes has been gathered and 14 groups of entire analysis samples of salty and fresh groundwater quality have been taken. In combination with the former correlative research and with the application of space analyses method of MAPGIS, water quality analysis method, mathematical statistic method and so on, the dynamical evolvement of groundwater, the change of groundwater quality and the interface of salt and fresh water downgoing have been studied in this paper. In the last more than 30 years, groundwater overexploitation caused the continual decline of deep groundwater head, the difference between the head of deep groundwater and the shallow groundwater above 40 m, and the change of groundwater quality and the interface of salt and fresh water downgoing. After calculation the average yearly numerical value of the interface of salt and fresh water downgoing is 0.4 m.The GM(1,1) model has been used to forecast the change of groundwater quality and the interface of salt and fresh water downgoing in the typical area. The buried depth of the interface will decline 12m averagely by 2020, with yearly average decline by some 0.6 m and 50% increase comparing with 0.4m of average decline over previous 30 years. If the effective measures are not taken, the interface of salt and fresh water will decline quickly.Therefore, in the middle and eastern plain of North China should enlarge the use of the salty water and the micro salty water for reducing deep groundwater mining quantity. This measure both can increase the water resources utilization and may alleviate the declining tendency of the interface of salt and fresh water.