Numerical modeling of ground thermo-hydrological changes in two Tibetan catchments and implications for lake level changes

Across the Qinghai-Tibet Plateau, arid and cold conditions provide permafrost and seasonally frozen ground. In recent decades changing climate led to substantial hydrological changes and strongly variable lake levels in the region which again strongly impacts the local population and settlements. This study focuses on two endorheic lake catchments, lake Paiku and lake Hala, to advance the representation and understanding of the connection between increased evaporation, runoff, and changing thermal states of the ground using a 1D numerical permafrost model. Additionally, to ameliorate the scarcity of data and measurement points for ground ice content and to compare the model output to field data, a novel remote sensing approach is utilized. Here, the seasonal amplitude of frost heave and thaw subsidence measured through satellite-based Interferometric synthetic aperture radar (InSAR) is used to estimate the potential for ground ice content in the active and the seasonally frozen layers of permafrost ground and translated to predict ground ice content within the permafrost table together with landform information from geomorphological mapping.

This provides a tool to estimate how large the impact of changing permafrost hydrology and the loss of ground ice content might be on local lake levels and, ultimately, on settlements and societies in arid high mountain regions which are highly vulnerable to small changes in the hydrological system.