Analysis of groundwater flow in mountainous, headwater catchments with permafrost

Abstract

Headwater catchments have a direct impact on the water resources of downstream lowland regions as they supply freshwater in the form of surface runoff and discharging groundwater. Often, these mountainous catchments contain expansive permafrost that may alter the natural topographically controlled groundwater flow system. As permafrost could degrade with climate change, it is imperative to understand the effect of permafrost on groundwater flow in headwater catchments. This study characterizes groundwater flow in mountainous headwater catchments and evaluates the effect of permafrost in the context of climate change on groundwater movement using a three-dimensional, finite element, hydrogeologic model. The model is applied to a representative headwater catchment on the Qinghai-Tibet Plateau, China. Results from the model simulations indicate that groundwater contributes significantly to streams in the form of baseflow and the majority of groundwater flow is from the shallow aquifer above the permafrost, disrupting the typical topographically controlled flow pattern observed in most permafrost-free headwater catchments. Under a warming scenario where mean annual surface temperature is increased by 28C, reducing the areal extent of permafrost in the catchment, groundwater contribution to streamflow may increase three-fold. These findings suggest that, in headwater catchments, permafrost has a large influence on groundwater flow and stream discharge. Increased annual air temperatures may increase groundwater discharge to streams, which has implications for ecosystem health and the long-term availability of water resources to downstream regions.

Estimating interaction between surface water and groundwater in a permafrost region using heat tracing methods

“…Many groundwater modeling studies in permafrost regions have reported on the subsurface fluxes, including soil drainage and recharge, and suprapermafrost flow. These studies have also shown that SW-GW exchanges can increase as the 10 active layer thickening, with water uptake into suprapermafrost aquifer occurring when subpermafrost hydraulic heads rise (Bense et al, 2009(Bense et al, , 2012Evans et al, 2015;Ge et al, 2011). Although our observations did not demonstrate the impact of changes to the permafrost table, our results show increasing interactions between SW-GW with active layer thawing.…”

“…Groundwater contributes significantly to stream baseflow, with most groundwater flow presented as a suprapermafrost aquifer (Evans et al, 2015). Many groundwater modeling studies in permafrost regions have reported on the subsurface fluxes, including soil drainage and recharge, and suprapermafrost flow.…”

What controls the partitioning between baseflow and mountain block recharge in the Qinghai‐Tibet Plateau?

“…With the increasing demand on limited water supplies, particularly in arid and semiarid regions, the potential effects of climate change on water resources in mountainous regions have received considerable attention in recent years [Brooks et al, 2015;Evans et al, 2015;Viviroli et al, 2011;Zhang et al, 2016]. In many large watersheds, surface water and interbasin groundwater flows, which originate from mountainous areas, provide the major sources of water for densely populated downstream alluvial plains.…”

Effects of Permafrost Degradation on the Hydrological Regime in the Source Regions of the Yangtze and Yellow Rivers, China

“…Wellman et al [18] demonstrated that permafrost thaw could accelerate rates of groundwater flow in the active layer above permafrost. Evans et al [19] suggested that an increase in mean annual surface temperature of 2 • C could cause a three-fold increase in groundwater contribution to discharge.…”