IWRA Proceedings

(a) Purpose or objectives and status of study or research hypothesis

1. To forecast twenty-first century changes in groundwater storage dynamics (seasonality) in a proglacial aquifer in response to climate change and glacier retreat.
2. To establish the principal drivers of these changes with particular focus on diffuse recharge (driven directly by climate) and focused recharge from glacier-fed river channels (driven principally by shifts in meltwater runoff dynamics due to glacier retreat).

(b) Key issue(s) or problem(s) addressed

Proglacial aquifers are increasingly recognised as important components of water cycling and storage in glacierised mountain catchments. The response of these aquifers to long term climate variability is complex and uncertain: driven in part by perturbations in diffuse recharge from rainfall and snow melt, and in part by perturbations in focused recharge from glacier-fed river channels as a consequence of glacier retreat. Therefore, forecasting climate change impact on proglacial aquifer storage dynamics must consider linkages along the climate-glacier-groundwater response cascade. This cascade remains poorly understood, partly because it necessitates the implementation of a sophisticated, integrated numerical modelling framework and because such a framework can only be validated with observation data that are rarely available in glaicerised catchments. This study addresses both of these issues.

(c) Methodology or approach used

A novel integrated modelling framework is used which consists of a glacio-hydrological model to simulate glacier dynamics and meltwater runoff and a distributed MODFLOW model to simulate proglacial groundwater storage dynamics and surface-groundwater interactions. The framework is driven by state-of-the-art climate projections and applied to a well-characterised and monitored glacierized catchment in south-east Iceland which is indicative of glacierized basins in temperate environments.

(d) Results and conclusions derived from the project

• Meltwater-fed river channels are a significant source of proglacial groundwater recharge. In the study catchment, the meltwater channel provides up to 20% of cold-season recharge.
• Glacier retreat and the reduction in meltwater runoff result in the flattening of diurnal river flow variations which could inhibit river recharge in the future.
• Proglacial groundwater dynamics under climate change in this temperate study catchment will be resilient to changes in meltwater runoff.

(e) Implications of the project relevant to selected conference theme, theory and/or practice

The study provides quantitative evidence for the susceptibility of proglacial aquifer storage to climate change and glacier retreat. It also provides process-based evidence for potential linkages between glacier retreat and aquifer resource vulnerability. In glacierised regions,
glaciers are typically considered the principal water source while proglacial aquifers have been largely neglected. This study highlights how proglacial aquifers could become strategically important as a water source as meltwater runoff inputs from glaciers become less reliable.