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Hydropower helps control spring flooding and climate change

Simon-Erik Ollus 24 March 2020, 15:46

Our energy system needs hydropower as regulating power alongside the growth in wind and solar power. Hydropower is also an effective means of controlling spring flooding.

Water and icy rocks

Climate change will lead to milder winters and increased rainfall. At the same time, hydropower’s production conditions will change: as the climate warms and the rainfall increases, Nordic water resources will increase.

The water volumes in winter in the Nordic countries will increase to the point that the central lakes and outlet rivers of water systems will flood. Warmer winters will delay the freezing of rivers, which will increase frazil ice* floods during heavy winter frosts.

Hydropower is an effective means of controlling increasing spring flooding

In Lapland, precipitation will increase the snow cover, but in the long term, the rising temperatures will melt the snow. The previous year is a very real example of the changing role of water resources: in the spring of 2019, the masses of rapidly melting snow in northern Finland highlighted the importance of flood control. The same development continues, as Lapland is threatened by heavy spring floods this year as well.

Regulated rivers are significantly helpful in preventing floods in water systems and reduce ice jams from forming. Kemijärvi Lake in northern Finland is a good example; in its natural state, it floods every spring. During peak flood periods in spring, the water levels may have been as much as 4 meters higher than water levels during autumn. With the construction of hydropower, regulation has decreased peak flood levels and has shifted their occurrence from spring to early summer.  

The impact of regulation is very visible in Rovaniemi, Finnish Lapland, where regulation has decreased the flood risk since the melt waters of the Kemijoki and Ounasjoki rivers no longer merge simultaneously at the city of Rovaniemi.

Hydropower is needed alongside other renewable energy sources

Emission-free energy has a vital role in solving the climate challenge. The share of solar and wind power in our electricity system is increasing significantly: for example, Nordic wind power production is expected to triple in ten years.

However, solar and wind power are variable, which is why renewable regulating power production is needed. Hydropower is a reliable regulating power and, as such, a resource that can be used in fighting climate change alongside other renewable energy sources.

In the future, electricity demand will grow in summer

Climate change means warmer winters but also longer summers. The summer of 2019 was very dry in the Nordic countries, which significantly raised the price of electricity. We were close to a power shortage when the Olkiluoto nuclear power plant was disconnected from the main grid due to a fire caused by a transformer.

In the future, electricity demand is likely to grow in summer, as global warming will increase the cooling need for houses and business premises. Data centres, which form the infrastructure of digitalisation, do not go on summer holidays, either. Traditionally, peak demand has mostly been covered by combined heat and power (CHP) production, but in the future, we will need regulating power all year long, which will increase the relative value of hydropower.

Hydropower operating conditions must be secured

In order to secure hydropower generation also in the future, we must find new solutions to reconcile the different perspectives related to the use of water systems. When it comes to regulating water systems, shifting to a more dynamic approach could be considered. As we will have increased water resources in winter, it is possible to produce more electricity during cold periods, as well.

It is essential to secure the current hydropower operating conditions by not limiting the use of the power plants for regulating production with additional provisions that control water flow rates. Solutions could be developed for the challenge of reconciling the needs of the fishing industry and hydropower production with the help of water biodiversity compensation models.

Traditionally, hydropower has secured the Nordic electricity system. In addition, we have trusted our neighbours to lend a hand in case our own production is not enough. Now, the fight against climate change is forcing us to re-evaluate the role of the traditional, emission-free and renewable hydropower. The importance of hydropower as a domestic resource maintaining the electricity system will grow. That is why we must do our best to make the most of hydropower in the fight against climate change.


Frazil ice is created when the water temperature of a river is zero or sub-zero and the river doesn't have a solid ice cover. When it snows in these conditions, the ice crystals don't melt when as they come into contact with the water, they freeze. The frozen ice crystals then start sticking to each other and frazil ice forms in the water. The frazil ice easily accumulates on river bank rocks and especially on the metal parts of a hydropower plant, blocking water flow and raising the water level.

Simon-Erik Ollus

Vice President, Trading & Asset Optimisation
simon-erik [dot] ollus [at] fortum [dot] com

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