The researchers studied how transferred water affects the quality of surface water and groundwater in Baiyangdian Lake, North China. They found that shallow groundwater quality is influenced by surface water, while deep groundwater quality remains stable. In areas with high nitrate levels, shallow groundwater can recharge deep groundwater. Rock weathering and evaporation processes dominate the water chemistry. The deep vadose zone in the alluvial fan exchanges Na+ with soil during surface water leakage. Transferred water improves surface water quality and recharges groundwater, which is crucial for irrigation and drinking in regions with frequent water transfers and groundwater exploration.