Impact of transferred water on the hydrochemistry and water quality of surface water and groundwater in Baiyangdian Lake, North China

The hydrochemical composition of surface water and groundwater is a key parameter for understanding the evolution of water and its quality. In particular, little is known about the impact of transferred water on surface water and groundwater. In this study, Baiyangdian Lake was selected as a typical area for extensive groundwater exploration and surface water transfer in the North China Plain. Surface water and groundwater samples were sampled in dry/wet seasons and then analyzed before/after the water transfer, respectively. Generally, surface water and groundwater are extensively hydrologically connected based on hydrochemical evidence. It was found that the hydrochemical composition of the shallow groundwater is affected by the surface water and that the water quality of the deep groundwater is stable. However, inter-aquifer recharge processes from the shallow groundwater to the deep groundwater existed in the anthropogenic region impacted with high nitrate-ion concentrations. Also, the hydrochemical composition of the surface water and groundwater was dominated by rock-weathering and evaporation-precipitation processes. Due to the existence of the deep vadose zone in the alluvial fan, Na⁺ was exchanged into soil matrices during the leakage of the surface water. In addition, the transferred water resulted in surface water with good quality, and it also played as an important recharge source to groundwater. As the most important water resource for irrigation and drinking, deep groundwater should be paid more attention in the alluvial fan with frequent water transfer and extensive groundwater exploration.