Climate change and hydropower: more water in winter

The impacts of climate change on hydropower are already being felt. Rising temperatures, melting glaciers and changing precipitation patterns are influencing the water availability in the mountains – and therefore also the production of renewable electricity. But how exactly are these changes affecting BKW's run-of-river power plants?

To obtain an answer to this question, BKW subjected its run-of-river hydropower portfolio to a comprehensive assessment. Based on the CH2018 climate scenarios and the HydroCH2018 hydrological projections, Aline Baumann, Environmental Specialist Hydro at BKW, and Christian Müller, former Portfolio Manager at BKW, modelled various future scenarios – from strong climate protection through to unchecked emissions. The focus was on the coming decades, in particular on the mid-century and end-of-century time horizons.

More winter electricity, but also new challenges

The key finding: over the course of the year, hydropower production is likely to remain relatively stable, but seasonal shifts are to be expected. There is a shift towards earlier maximum run-off in summer. While water levels are generally expected to fall in summer, run-off is likely to increase in winter. This effect is particularly clearly visible in Alpine regions such as Kandergrund. “We have now carried out a detailed assessment for the first time, based not just on a feeling but on specific models,” explains Aline Baumann. “This confirms the assumptions we had previously: the volumes of water are shifting over the course of the year, but annual production is likely to remain relatively stable.”

One positive aspect of this development is that hydropower production in winter could increase. This means more renewable energy at a time when Switzerland already has higher electricity demand. However, the climate-related changes also carry risks. More frequent extreme events such as heavy rainfall or flooding could lead to large volumes of water flowing away unused – a challenge for the planning and management of the plants. “Yes, we expect more water in winter in the future – but that does not automatically mean more electricity production,” says Baumann. “If too much water arrives all at once, it can trigger flooding. Such extreme events are increasing, but their distribution is difficult to predict, and that is precisely a major challenge for operating power plants.”

What does this mean for cost-effectiveness?

The assessment examines not only the production volume, but also cost-effectiveness. The so-called net present value (NPV) – in other words, the financial value of the plants taking into account future revenues and costs – was calculated for various climate scenarios. The results show that run-of-river hydropower plants can remain a stable investment despite climate change.

If climate protection is not strengthened, the so-called water availability could decline in the long term – with negative impacts on production and economic returns. Above all, the melting of glaciers, which currently still serve as natural water reservoirs, represents a major uncertainty. “By the middle of the century, we expect more water in some Alpine regions – especially where there are still glaciers in the catchment area,” says Baumann. “But at some point these glaciers will be gone. Then this additional water will be missing, and that is a major challenge for the long-term use of hydropower.”

Hydropower remains important, but we must act

The study clearly shows that hydropower remains a central pillar of Switzerland’s energy supply, but it is facing changes. Seasonal shifts and extreme events must be taken into account in future planning in order to ensure sustainable and economically stable electricity production. The analysis also makes it clear that without climate action, there is a risk of a long-term decline in water availability. The glaciers, which still serve as natural reservoirs today, will disappear. This makes it all the more important to take action at an early stage – for a secure and sustainable energy future. “Hydrological scenarios show that if we do nothing now, water availability will decrease in the long term. This means less production and growing challenges for our power plants,” Baumann summarises. “That is why climate action is not only an environmental issue, but also an energy issue.”

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