Groundwater and streamflow sources in China's Loess Plateau on catchment scale

Abstract

Water sustainability is a major challenge on China's Loess Plateau since drying of soil water and runoff is threatening regional water security. Fundamental to effective water management is an understanding of groundwater and streamflow recharge, storage and fluxes. We investigated groundwater – streamflow connectivity and groundwater recharge mechanisms using stable isotope analysis (δ2H and δ18O) of groundwater and streamflow through the dry season in five large catchments (7636–60,916 km2) of the Loess Plateau. We found that streamflow and groundwater stable isotope compositions overall vary across catchments and within each catchment primarily explained by hydrogeological conditions and climatic gradients. The streamflow is sourced from a similar groundwater reserves across four catchments with thick (>100 m) loess cover. The groundwater is likely to be recharged by local precipitation, but it is a mixture of ancient and modern water. This catchment-scale analysis has provided new insights into groundwater recharge mechanisms in regions with thick unsaturated zones and large subsurface water storage, which provides useful information for water resources management.