23.03.2017 | How climate change impacts hydropower
Droughts, heat waves, heavy rains and hurricanes – the climate is changing and the weather is out of hand. In what form are these phenomena occurring in Switzerland, and what are the impacts on hydropower?
Tornados in the South of the USA, flooding in Italy, tropical storms on the Fiji Islands – hardly a year goes by without media reports of severe weather conditions. These episodes are increasing on a worldwide scale.
In Switzerland, hurricanes have laid waste to entire regions and hillside slopes have turned into mudslides taking everything in their path with them down to the valley. Are these types of weather phenomena increasing due to climate warming?
SRF meteorologist Felix Blumer reassures us: In recent years, no increase in severe weather conditions has been found. According to Blumer the last large-scale rainfall disaster took place in Switzerland in August 2005 with great damage in Central Switzerland and the Bernese Oberland. From then on, only local events have occurred such as the flooding in Lyss in the summer of 2007 or high waters in the Kandertal in October 2011. „We do not have to expect a significant change in event frequency in the upcoming years," asserts the meteorologist.
Even though climate change does not cause more bad weather, it still leaves obvious traces. Glacier shrinkage is the most evident: Alone in 2016, glacier volume decreased by 1.5 %.1
Weather expert Felix Blumer confirms that glaciers continue to dwindle: „By the beginning of the 22nd century, only small glacier areas will exist in Alpine regions. Studies indicate that glacial melting in glacial riverbeds will still, for the most part, be able to compensate dry summers until 2050. After that, the glacier areas will be too small and Switzerland will be increasingly impacted by drought periods."
Hydropower plants supplied with glacier water will be primarily affected: Reservoirs. According to the SRF meteorologist, they can expect additional melt water from glaciers until the year 2050. As a rule, overall warming moves the snowline up to higher altitudes. As result, the periods of direct water flow from mountain and alpine areas will become longer. In addition, due a higher snow-melting rate, the snow cover will not necessarily remain for the entire season. „Owing to general warming, we see a trend to water flow throughout the year with the advantage that the risk of high waters in spring will sink because the same snow melt volumes are no longer available," says Felix Blumer.
Certain hydropower plants have water catchments that are located directly under the glacier. The change in melt water volumes can be observed closely here, explains David Brunner, Head of Core Market Axpo Trading. The difference in the snow cover height can be seen in many storage power plants based on measurements taken last year and in the current year. As compared to the past, in recent years heavy snows only occurred during the period from February to March, and ultimately a snow cover thickness corresponding to the multiyear average was achieved. „This year, the average amount of snow in the mountains is much less than at the same point in time last year. If there is no more precipitation, the snowmelt will produce less flow to the various power plants, which will have a direct impact on power plant utilisation. However for market price formation, demand is as important as supply. As a result, the impact of reservoir water shortages on the future spot market price cannot yet be determined," reports David Brunner.
The seasons tend to shift back in a clockwise direction throughout the year. The logic behind this is physical: „At higher temperatures, the atmosphere can absorb more water vapour. The more water vapour in the atmosphere, the slower its reaction to temperature fluctuations. We can verify this by comparing the development of water temperatures to air temperatures. This effect has been confirmed by climate statistics," explains Felix Blumer.
But weather and climate are not the same things. Peaks and deviations from the trend will always occur. For example, in Switzerland we experienced the highest yearly temperatures in 2014 and 2016 in June. The situation in the summer of 2014 was particularly extreme, when the highest annual temperature was registered as early as Whit Monday, 9 June, even before the sun’s peak.
When it comes to snow, it would be wise not to make any hurried conclusions because according to expert Felix Blumer snowfall in the Swiss midlands is by far not a thing of the past, although after the snowless winters of 2015/16 and 2016/17, one might begin to think so. In the early 90’s, winters already had quite little snow, and at the beginning of the 70’s snow shortages were a permanent topic. Overall warming does not per se represent a downward shift of the snow line. The snow line is not only dependent on temperature, but also on precipitation. In the winter of 2016/17, the lack of precipitation was primarily responsible for the snow shortage in Felix Blumer’s opinion. This year it snowed again at the end of February and the beginning of March.
So the Swiss will be able to continue skiing: Slightly later in the year, but until the end of March.
1Swiss Academies of Arts and Sciences: Media Release dated 3 November 2016