Especially during hot summers like the one in 2018, the Swiss glaciers are a precious source of water, in particular for hydropower production. But as we all know, glaciers are continuously retreating, meaning that they release water that was accumulated years to centuries ago, and that cannot be replenished by precipitation in the near future. Therefore, an interdisciplinary SCCER-SoE research team including glaciologists, hydrologists, and hydraulic engineers decided to quantify the following aspects: How strongly relies Swiss hydropower production on waters released by glaciers? How big are the local variations? How might hydropower production evolve in the future? To answer these questions, we needed to compile the most recent data sets on Swiss water resources and hydropower infrastructure, and on the glacier mass evolution in the past and in the future.
Less hydropower production because of glacier retreat by the end of this century
According to our estimates, since 1980 3.0 % to 4.0 % of Swiss hydropower production was directly provided by losses in glacier volume. This corresponds to between 1.0 and 1.4 TWh per year, or the annual electricity consumption of roughly 230,000 Swiss households. Glacier mass loss will continue to feed the Swiss hydropower plants in the future, but the production directly related to this contribution will drop to around 0.4 TWh per year by 2070-2090. In other words, the calculations anticipate a reduction in hydropower production of up to 1 TWh per year resulting from the fact that the glaciers will not continue to release such large amounts of waters as they do at the moment.
However, there are strong regional differences (Figure 1). In the Rhone river catchment, with its large valley glaciers, between 6.5 % and 8.5 % of the annual hydropower production stemmed from glacier mass loss in the recent past. This share is likely to only marginally decrease between 2040 and 2060, but will drop by half from 2070 to 2090.