Precipitation-soil water-groundwater connectivity under changed vegetation pattern in China's Loess Plateau

In regions with thick unsaturated zone and arid climate, the complicated subsurface hydrological processes and little water flux challenge the studies related to groundwater recharge. It is necessary to explore the recharge mechanism from different scales with multiple methods. The Loess Platea has loess deposits with mean thickness of ~100 m, and the groundwater recharge mechanism remains controversial in the past. We employed traditional monitoring of soil water and water table with multiple tracers to explore the connectivity among precipitation, soil water and groundwater. Vegetation change can substantially alter the hydrological connectivity. Because of the Grain for Green Project, the Loess Plateau has experienced large-scale vegetation change including increased vegetation cover and conversion from shallow- to deep-rooted plants. Previous studies have shown that the soil water has been depleted, however, its impacts on groundwater recharge remain unclear. We thus develop different techniques to quantify how vegetation changes influence the subsurface hydrological processes. The precipitation-soil water-groundwater connectivity is identified, and the impacts of vegetation change on the connectivity has been investigated.