Hydrogeochemical evolution of groundwater in the lake area of northern ordos cretaceous basin

Northern Ordos Cretaceous Basin has abundant mineral resources and now it is facing the problem of lacking water. An understanding of the evolution of the groundwater contributes to resource management. In view of the lake controlling action of groundwater evolution in this area, the paper finds out the relationship between the lakes and groundwater. Remote sensing image data, hydrochemical data and stable isotope data are combined to analyze the hydrochemical processes of the groundwater. The distribution of the lakes shows that more than 80% of the lakes are small ones, and most of them are formed in the depressions. Medium and large ones are formed in the regional drainage. The hydrochemical characteristics of the water in the lakes are Cl- Na type while the hydrochemical characteristics of groundwater varies from HCO_3- Ca· Mg· Na to SO_4- Na along the flow paths. The groundwater have the similar composition of hydrochemical composition of HCO_3- Ca· Mg and stable isotope signatures in Cenozoic group, Luohandong group and Huanhe group, which reveals that groundwater in these three aquifers have close hydraulic connection. The results suggest that the groundwater receives recharge from precipitation, and discharges into the lakes.