Evaluation Of Hydrochemistry Characteristics And Groundwater Quality In Dawukou District Of Shizuishan

Dawukou district of Shizuishan city in Ningxia is seated in arid area, whose imbalance between supply and demand of water resources is very conspieuous, and groundwater is one of main water sources. Based on reconnaissance and analysis of the groundwater chemistry data, the paper studied the hydrochemical characteristics of groundwater of Dawukou.The evolution and formation of chemical composition of ground- water were analyzed and discussed in detail. And the collected quality data of over years were used for water quality evaluation. The research results provided scientific base for reasonable exploration, utilization and protect of groundwater resources, which was significant to mitigate the shortage of water resources. The conclusions were summarized as following:1,The groundwater system of Dawukou district has changed gradually from the phreatic groundwater in the diluvial fan in front of the mountain to the phreatic water and confined water in the multi-layer structure region of the fluvial plain. According to the comprehensive hydrogeological conditions of Dawukou, the groundwater in this region is composed by four aquifers:the fist aquifer is overlying phreatic, the others are confined water.2,By studying the spatial distribution and chemical type of groundwater,the conclutions are obtained that dominant antion changes along the paths of water flow is in the order of HCO3-→HCO3-+SO42-→SO42-+HCO3-→SO42-+Cl-→Cl-+SO42-. The groundwater in the southwest shows strong leaching, deeply buried, less of mineralization and mainly bicarbonate. However, the groundwater in the northeast displays shallow water depth, strong evaporation, increasing salinity and mainly vitriol and chloride.3,According to the result of PHREEQC modeled results, the chemical species in groundwater and saturation indexes of minerals are obtained. The results showed that the dissolution of halite and desorpotion of Na+is dominant in entire path of the water flow. The calcite and dolomite have different infection for chemical composition of groundwater along different paths of water flow. 4,Studing on the formation of groundwater showed that the geology and hydrogeology conditions, soluble salt contant of rock, recharging water, evaporation and human activities influence and determine hydrochemical characteristics and evolution of groundwater of Dawukou.5,Using osculating value methods based on entropy weight to evaluate water quality of this region, the results showed that from horizontal direction, the phreatic groundwater in the westen diluvial fan is better than the easten fluvial plain. Besides, the quality of confined water is better than the phreatic groundwater. In vertical direction, with the increase of depth, the quality of deep confined water is better than shallow confined water.