Future effects of glacier retreat on downstream runoff and hydropower generation in the Alps

Due to climate change, glaciers are retreating worldwide. Among different consequences, the decline of meltwater in rivers will lead to a reduction in runoff. The aim of this work is to quantify the changes in runoff and the impact on selected hydropower plants in different drainage basins in the Alps until 2100.

Outputs from the Global Glacier Evolution Model (GloGEM), which uses 14 General Circulation Models to compute the future evolution of the glaciers worldwide, were used to determine past and future runoff from glaciers individual hydropower plants’ catchments. Measured runoff data at selected locations along rivers was used to compute the share of glacier runoff in total discharge. The computed river runoff was subsequently applied to determine the reduced electricity production of the hydropower plants.

The results reveal a decrease in summer runoff at all investigated power plants by 2100. However, large differences occur among the different catchments. In particular, geographical characteristics, such as glacier size and altitude, determine the intensity and timing of the decline. Areas located further away from glaciers, particularly in the North of the Eastern Alps, show the strongest reduction in glacier runoff (up to 86% compared to 1986-2015). In contrast, mountainous catchments and the South of the Alps are mostly affected by a decrease in river discharge (up to 33% compared to 1986-2015). Due to the dry summer climate, the summer runoff in these areas is reliant on the glacier discharge. This is also evident in the impact on hydropower production. For the run-of-river plants along the Rhone, one has to expect a decrease in summer production of up to 20%, which corresponds to an annual loss of € 5.3 Million. The losses are even higher for storage power plants located in catchments with a big glacier cover. For these, annual losses of up to € 35.0 Million were determined for the period 2071-2100.