Climate change, water resources and the hydropower system in Iceland

In Iceland, hydropower represents around 72% of the gross electricity generation annually, with energy production capabilities around 13.8 TWh/a. Most of the hydropower infrastructure is in the central highlands, relying on water resources temporarily stored as snow and ice. These resources are vulnerable to climate change, projected to undergo substantial changes in the coming decades. Changes in flow volumes, seasonality of flow and extremes will have a strong impact on the hydropower system in Iceland as over 50% of inflow energy to the system originates from glacier ablation during summer. The high natural climate variability and energy system isolation pose a risk to the energy security of the power system as droughts and cold periods are usually not foreseen with great advance. Changes in hydrological flow dynamics, e.g.: onset of snow- and glacier melt, melt magnitudes and precipitation patterns pose a series of challenges for the hydropower system. In glacier-dominated catchments, climate warming will initially increase glacier meltwater runoff to a maximum and then runoff will reside as the glacier area and volume decrease over time. The timing of the discharge peak is influenced by the catchment topoclimate characteristics and location. Understanding and quantifying these changes is important both for operational control and planning of energy infrastructure on shorter timescales (days, months, years) and climate change adaptation, on longer time scales, for both current energy projects as well as future development to maximize efficient water resource utilization. To assess the impacts of changes in inflow dynamics on the hydropower system, hydrological models were developed to create inflow scenarios. Historical inflows were first reconstructed, followed by a construction of future runoff scenarios using climate projections and different glacier geometry evolution. This allowed for the assessment of meltwater-induced changes in runoff, although generally increasing in the next decades, certain areas are closer to reaching maximum meltwater production and will decrease in the coming decades. In all cases meltwater-induced increase in runoff is temporary, while large uncertainties exist with the timing of maximum peak inflow. Utlization of the inflow scenarios created include current day operation to optimize reservoir management strategies and the design of future power projects, including refurbishments and capacity increases. This accommodates the expected increased flow rates 10–50 years into the future.