This presentation first examines the dynamics of groundwater in Tibet at the regional scale. Then, it focuses on groundwater at shallow depth that is affected by permafrost thawing under warming. The aim is to shed lights on how groundwater dynamics changing under warming.

At the regional scale, groundwater flow is driven by topography and sustained by recharge at headwater regions. Such regional-scale groundwater involves travel distances of hundreds of kilometers to depths of kilometers. Faulted and fractured rocks and unfrozen talik below river valleys promote hydrologic connections between deeper groundwater and surface waters in the form of springs and baseflow to streams.

Groundwater at shallow depth is readily influenced by thawing permafrost underlying the Tibet Plateau. Numerical modeling was used to examine the response of coupled heat transport and groundwater flow to permafrost thawing. Model results show that ground freezing in colder seasons reduces aquifer permeability and lead to little groundwater discharge to streams. In warmer seasons, groundwater flow is invigorated in supra-permafrost aquifers as permafrost thawing enhanced hydraulic permeability and new liquid water liberated from thawing, leading to more groundwater to steams as baseflow. Heat is transported by conduction and advection due to mobilized groundwater.

As warming continues, enhanced groundwater discharge to streams can be expected in coming decades. This potential bounty, however, would last only as long as there are sufficient recharge sources from glacial or snowmelt to replenish groundwater flow. Long term scarcity is a more likely when the recharge from glacier or snowmelt to groundwater diminishes.