Hydrochemical and Isotopic Explanations of the Interaction between Surface Water and Groundwater in a Typical-Desertified Steppe of Northern China

Abstract

The Tabu catchment, a typical-desertified steppe in China, was selected as the study area to qualitatively analyze the interaction between surface water (SW) and groundwater (GW), and an integration of hydrochemical analysis and isotopic techniques was applied. The results show that the ion contents in SW and GW increased from upstream to downstream, and the hydrochemical evolutions were both controlled by rock weathering and influenced by evaporation. The δD–δ18O lines of SW and GW were δD = 5.14δ18O − 24.68 and δD = 6.89δ18O − 5.81, respectively. Along the I–I′ profile, the contents of most indices, δD and δ18O in SW and GW both showed increasing tendencies. All of the similarities in the hydrochemical characteristics and isotopic techniques indicated that SW was recharged by GW. The δD–δ18O inconsistency in SW and GW samples from midstream and downstream areas indicated that SW did not recharge to GW in these areas and was consumed by evaporation or replenished the moisture in the vadose zones. The runoff decreased, which was mainly caused by excessive exploitation of GW and a decline in the GW level. This study deepens the understanding of the hydrological cycle and provides guidance for the optimal combined utilization of SW and GW.