Climate Warming Driven Changes in the Cryosphere and Their Impact on Groundwater-Surface Water Interactions in the Heihe River Basin

The Heihe River Basin in Northwestern China depends heavily on manmade and natural storage like surface reservoirs, rivers, and groundwater for economic and environmental functions. The Qilian Mountain cryosphere in the upper Heihe River Basin is integral to recharging these storage supplies. Climate change driven shifts in high elevation water storage are expected to have significant impacts on water supply in the Heihe River Basin. To examine the impacts of these shifts, we built a hydrologic model using ParFlow-CLM of the middle basin, which encompasses over 90% of water usage. Using this model, we ran 4 simulations over the period of 2001 to 2011. These simulations are meant to model impacts of streamflow changes due to the loss of glaciers and advanced permafrost degradation on the middle basin. First, we ran a baseline scenario which uses unaltered streamflow data of all gaged streams entering the middle from the upper basin as input. Then, we ran three scenarios one with a 15% streamflow reduction in the thawing season (April to October) to represent the loss of glacial contribution to streamflow. The next with a 50% baseflow increase year-round to represent the response to permafrost degradation. The last scenario applies both perturbations. Results show enhanced groundwater discharge when flow is reduced, and infiltration when flow is increased, with a diminishing role of the subsurface over time and more of the streamflow change passing through. Seasonal trends show different behaviors in groundwater-surface water partitioning due to glacial loss and permafrost degradation. Additionally, flow changes due to permafrost degradation are expected to outweigh those resulting from glacier loss. Ultimately, this analysis can be used to examine the cascading impact of climate change in the cryosphere on the resilience of water resources in arid basins downstream of mountain ranges globally