Critical Role of Groundwater Inflow in Sustaining Lake Water Balance on the Western Tibetan Plateau

It is difficult to quantify the amount of groundwater inflow on the Tibetan Plateau (TP), yet it can be critically important for sustaining lake water balance. Here we show that most endorheic lakes on the western TP exhibited considerable water level increase during the ice-covered period, which contrasts with lakes in other regions of the TP. An analysis of lake water balance attributes this water surplus to significant groundwater inflow, which is estimated to be about 59%-66% of total inflow into lakes. The groundwater inflow occurred after the 2000s, which is consistent with the rapid lake expansion and significant increase in precipitation. We suggest that the groundwater inflow is mainly related to large-scale active faults in the limestone bedrock and sufficient meltwater from high elevations. Our results imply that groundwater may be deeply involved in the water cycle and modify the seasonal and inter-annual lake variations on the western TP.