Assessing the sustainability of mountain groundwater resources under conditions of permafrost degradation and glacial recession

Mountain regions, characterized by glacial and periglacial features, constitute a major global freshwater resource, yet climate-driven changes in the magnitude and timing of groundwater discharge threaten large-scale water resource sustainability. Though the widespread retreat of mountain glaciers and degradation of permafrost are well-documented, their individual and combined influences on groundwater systems remains poorly understood. Quantifying the temporal and spatial relationship between glacial melt, permafrost extent, groundwater discharge, and streamflow is necessary to assess the sustainability of streamflow under changing climate conditions. We present a two-dimensional coupled groundwater flow and heat transport model with seasonal freeze-thaw capability using the United States Geological Survey SUTRA 4.0 modeling software to investigate how warming air temperatures influence groundwater discharge patterns from a permafrost-affected aquifer recharged by glacial meltwater. The model represents a hillslope-valley cross-section adjacent to a small alpine glacier in the Rocky Mountains of Colorado, USA. The model is forced with baseline and observed warming air temperature scenarios and explicitly resolves the relative importance of permafrost thaw, seasonally-variable recharge, and changes in glacial meltwater contribution to groundwater discharge patterns to an alpine lake. Results suggest that interactions between a saturated glacial meltwater recharge zone and the adjacent permafrost hillslope may drive groundwater discharge seasonality and contribute to talik development beneath the hillslope. Simulations assess sensitivity to warming rate, permafrost thickness and continuity, and the timing and magnitude of glacial meltwater recharge.

This research provides process-based insight into mountain groundwater flow dynamics in areas of degrading permafrost and glacial features, and helps clarify the role of glacial meltwater recharge in sustaining mountain-derived streamflow under elevation-dependent warming. Results will inform predictions of hydrologic resilience and water resource sustainability in alpine watersheds, which are experiencing rapid environmental change.