Opportunities for hydropower under climate change in snow-ice dominated landscapes: case of the Hálslón Catchment Kárahnjúkar Hydropower Plant in eastern Iceland

Northern landscapes like the Arctic regions of Northern Europe, Canada and Iceland, are especially susceptible to the effects of climate change, considering accelerated glacial melt due to increased temperatures. Glacier melt will inevitably change the runoff regimes of northern catchments, with increased streamflow in the near future. This increases flooding hazards but also bears economic opportunity with increased hydropower potential.

This study examines the future hydrological dynamics of the Hálslón catchment in eastern Iceland, focusing on the impacts of climate change on streamflow and hydroelectric potential. 70% of the 1’615 km² catchment are covered by Vatnajökull, Europe’s largest glacier. The catchment drains into the Hálslón reservoir, the main lake of the Kárahnjúkar Hydropower Plant system, a 690 MW facility that produces nearly a quarter of Iceland's electricity.

Using the semi-distributed HBV-Light hydrological model, we performed 10,000 automatic Monte-Carlo calibration runs with a multi-objective approach, optimizing both discharge and glacier mass balance. Future streamflow scenarios were simulated for 2015–2100 using 12 climate models, three Shared Socioeconomic Pathways (SSP2-4.5, SSP3-7.0, SSP5-8.5), and the 10 best parameter sets derived from calibration to address uncertainties.

Preliminary results indicate a potential doubling of annual inflow to the Hálslón reservoir by the end of the century, driven by intense glacier melt and changing precipitation patterns. This excess flow, currently unutilized and discharged via spillways, represents significant untapped hydroelectric potential. At present, excess flow accounts for up to 20% of yearly inflow but could rise to over 50% by century’s end, according to modeling projections. The substantial increase in streamflow underscores the need for adaptive management strategies to optimize Iceland's hydroelectric infrastructure, leveraging emerging opportunities for renewable energy production. This research demonstrates the integration of hydrological and climatic models to evaluate the impacts of environmental change on vital water resources.