Evaluation of surface water and groundwater interactions in the upstream of Kui river and Yunlong lake, Xuzhou, China

Understanding the interaction between groundwater and surface water is of great significance to the rational development and utilization of water resources and the protection of ecological environment. Here we present a combination of several methods (radon balance method, EC conservation method and flow balance method) for evaluating the hydraulic exchange of groundwater and surface water in a small watershed of Kui river and Yunlong lake. The exchange fluxes of Kui river, Yunlong lake and groundwater were estimated by one-dimensional steady state model and box model. The results indicate that the lake water is mainly recharged by groundwater from the surrounding mountains and the lake renewal time is approximately 26 days. Meanwhile, multiple transformations occur between groundwater and river water, and river water leakage is dominant. The existence of several tributaries complicates the hydraulic exchange, and groundwater discharge is also evident. Furthermore, the advantages and disadvantages of these three methods were analyzed. This study successfully demonstrated that radon and EC as tracers can be used to estimate the exchange flux between groundwater and surface water, particularly in areas lacking conventional hydrological data. Combining these three methods, the hydraulic exchange between groundwater and surface water can be evaluated more effectively. The analysis of hydraulic exchange is also crucial for Xuzhou area where water resources are extraordinary scarce and polluted.