Groundwater salinization characteristics and controlling factors in the Haiyuan Basin

Groundwater is the dominant resource of water supply for meeting domestic needs in the Haiyuan Basin. In recent years, the increasing salinity has been found in groundwater around some areas, to which high attention has been pain by the relevant departments and hydrogeologists. Determining the distribution of groundwater total solved solids and understanding the salinization mechanism are important for water supplies and sustainable development. Isotopic and geochemical analyses are conducted for 69 water samples from springs and boreholes to identify groundwater recharge sources and potential processes that control the increasing salinity. The results show that the total dissolved solid (TDS) in the groundwater range from 198.2 to 6436.4 mg/l and increase along the groundwater flow path. The hydrochemical types evolve from HCO3—Ca·Mg type in the bedrock area to SO4·Cl—Na·Mg type in the discharge area. The sources of natural groundwater recharge include precipitation and lateral groundwater flows from the mountain areas in the southwest of the basin, both of which have minor contributions to the groundwater salinity. Carbonate and silicate weathering plays a dominant role in the bedrock recharge area, and evaporate weathering, in the flow-through and discharge area. The contribution ratios of the initial water, dissolution and evaporation to TDS of the groundwater vary from 4.8% to 81.2%, 11.9% to 85.9% and 1.7% to 29.5%, respectively. The dissolution process is the first order controlling factors on the groundwater salinization in the Haiyuan Basin. It is suggested that the springs in the bedrock area should be developed and the groundwater exploration should be adjusted in Haiyuan County and Xi′an village to prevent salinization. Furthermore, the technology that can remove sulfate from groundwater should be introduced in the areas where brackish water exists.