Characterizing the interaction of groundwater with surface water and precipitation in the Mongolian Plateau in China

Due to the arid climate, groundwater is a vital water resource for ecosystems such as those associated with Dalinor Lake in the Inner Mongolian Plateau, China. This research studied the groundwater circulation mechanisms in Dalinor Lake and surrounding areas and their contribution to surface water, based on remote sensing and environmental isotopes analyses. Using Landsat satellite data, it was found that the lake area of Dalinor Lake decreased by 12% between 1986 and 2021. The shrinkage rate increased from 0.31 km 2 /year in 1986–2005 to 1.24 km 2 /year in 2005–2021. The groundwater contribution to the lake is 1.49 × 10 8 m 3 /year. Soil profiles and a rainfall simulation test revealed that precipitation infiltration provides limited recharge to groundwater. The groundwater stable isotopic signature (δD = –88.55‰, δ 18 O = –10.01‰), which is more depleted than local precipitation (δD = –63.83‰, δ 18 O = –8.76‰), implies that local precipitation is not the main source of groundwater recharge. The groundwater stable isotopic signature in different river sources is diverse, indicating the spatial specificity of groundwater recharge sources. Groundwater and river water have mantle-derived helium ( R / R a > 1) and high tritium concentrations, so it is speculated that groundwater in the Dalinor Lake and its surrounding area is recharged by modern precipitation (post 1960s) outside the study area through fast channels, such as fault systems. This study provides information necessary for effective water management in the Inner Mongolian Plateau.