Interaction between Surface Water and Groundwater in Yinchuan Plain

The interaction of surface water (SW) and groundwater (GW) is becoming more and more complex under the effects of climate change and human activity. It is of great significance to fully understand the characteristics of regional SW-GW circulation to reveal the water circulation system and the effect of its evolution mechanism to improve the rational allocation of water resources, especially in arid and semi-arid areas. In this paper, Yinchuan Plain is selected as the study area, where the SW-GW interaction is intensive. Three typical profiles are selected to build two-dimensional hydrogeological structure models, using an integrated approach involving field investigation, numerical simulation, hydrogeochemistry and isotope analysis. The SW-GW transformation characteristics are analyzed with these models, showing that geological structure controls the SW-GW interaction in Yinchuan Plain. The SW-GW flow system presents a multi-level nested system including local, intermediate and regional flow systems. The runoff intensity and renewal rate of different flow systems are evidently different, motivating evolution of the hydro-chemical field; human activities (well mining, agricultural irrigation, ditch drainage, etc.) change the local water flow system with a certain impacting width and depth, resulting in a variation of the hydrological and hydro-chemical fields. This study presents the efficacy of an integrated approach combining numerical simulation, hydrogeochemistry and isotope data, as well as an analysis for the determination of GW-SW interactions in Yinchuan Plain.