Hydropower in Finland
Hydropower is a domestic and renewable form of energy. There are about 250 hydropower plants in Finland, and Finland’s total hydropower capacity is about 3 190 MW.
In recent years, hydropower has accounted for around 15-25% of domestic electricity production. According to Statistics Finland’s preliminary data, in 2024 hydropower would account for about 17.0% of Finland’s electricity production, with a total of about 14,147 GWh of electricity produced by hydropower in 2024.
There is still potential for further hydropower development in Finland, although most of the major sites have already been built. However, significant new hydropower development is unlikely for environmental and nature conservation reasons.
The most cost-effective way to increase hydropower capacity is to increase the capacity of existing plants by renovating the main machinery. The majority of the additional potential of already built hydro can be obtained by increasing the capacity of the plants.
In terms of production costs, hydropower plants are cost-effective due to their long lifetime. The capital costs of old power plants have already been amortised, so that only the operating and maintenance costs are paid.
Environmental impact
Many of the impacts on the environment and aquatic nature caused by hydropower plants are local. The hydropower plant and any reservoir that may be built around it will affect the ecological balance of the harnessed water body and the land below the reservoir. The native biota in these areas will either be destroyed or displaced. In many cases, the construction of reservoirs will also result in the displacement of human settlements. Harmful substances, including heavy metals, present in the soil of the areas under the reservoir often dissolve in the water and eventually accumulate in fish and other biota.
In addition to heavy metal accumulation, hydropower plants can also have other adverse effects on fish stocks. Migratory fish may be prevented or hindered from reaching spawning rivers in dammed water bodies. However, well implemented fish ladders can reduce problems. Water level fluctuations caused by regulation can also affect fish spawning and fry survival.
Areas below the reservoir also release carbon dioxide and methane into the atmosphere, especially if the areas covered by water are not cleared of trees. Such greenhouse gas emissions are a bigger problem in warm tropical regions than in the cooler northern zones. Hydroelectric power generation itself does not produce greenhouse gas emissions, so greenhouse gas emissions from energy production can be reduced if fossil fuels are replaced by hydroelectric power.
Hydropower Technology
The kinetic energy of the water flowing down the waterfall of a hydropower plant is captured as the water flows downstream through the turbines. The kinetic energy is converted into electricity in the generators and then passed on through a transformer to the grid for use by consumers.
The operation of a hydroelectric power plant is based on the difference in height between the upper and lower basins of the plant. The waterfall can be natural or connected by dams and waterways from several sections of rapids. Waterfall heights vary greatly depending on the power of the plant. The typical head of a small hydropower plant is only 2-6 metres. In Finland, even large power plants typically have head heights of only a few tens of metres. The highest waterfall height, 96 m, is at the Jumisko underground power plant in Kemijärvi.
In the past, hydropower was often used to provide motive power directly to a piece of machinery, such as a mill or sawmill, but nowadays hydropower plants usually generate electricity.
Hydropower plants are divided into three size categories based on their capacity:
- plants below 1 MW are mini hydroelectric plants;
- 1-10 MW plants are small hydropower plants, and
- plants over 10 MW are large hydropower plants.
In Finland, the capacity of hydroelectric power plants ranges from less than one megawatt to 170 megawatts. The vast majority of hydropower plants in Finland are river or rationing plants. There are no suitable conditions for wave and tidal power generation in Finland.
One advantage of hydropower generation is that it can be used to smooth out peaks in electricity consumption, as energy can be stored by dams. Electricity generation can be quickly increased or decreased according to fluctuations in electricity consumption. In the case of run-of-river power plants, the reservoir created by the plant’s own dam can handle short-term regulation, while a rationing power plant can regulate production up to an annual level. Hydropower regulation can also be used to prevent spring floods.
Small Hydropower
Small hydropower can have regional significance, for example by improving local electricity security. Interest in small hydropower is fuelled by the need to replace fossil fuels to combat climate change. Small hydropower is also positive from the point of view of decentralised energy production. The downside of small hydropower is the negative impact it can have, particularly on stream habitats.
Small hydropower plants are divided into two size categories according to their capacity; actual small hydropower plants with a capacity of 1-10 MW and mini hydropower plants with a capacity of less than 1 MW.
In 2013, there were 151 small hydropower plants in operation in Finland, of which 68 plants have a capacity of less than 1 MW and 83 plants have a capacity of 1-10 MW. The combined annual energy production of these plants is around 1 000-1 100 GWh, depending on the water year.
The average output of small hydropower plants in Finland is about 2 MW and the average annual production is about 8 GWh. Of all the energy produced by hydropower, mini-hydropower accounts for about 1% and small hydropower for about 8% (Small Hydropower Association 2015).
Small hydropower plants have a long lifetime, typically 60-100 years.
Small hydropower potential in Finland
The remaining hydropower potential in Finland in unprotected water bodies is about 663 MW (2 352 GWh/a).
The remaining potential is divided into different size categories as follows:
- mini-hydropower (below 1 MW) 144 MW / 1 021 GWh/a;
- small hydro (1-10 MW) 144 MW / 392 GWh/a; and
- over 10 MW hydro 375 MW / 939 GWh/a.
In line with Finland’s energy and climate strategy, the potential for small hydropower is mainly based on modernisation and upgrading projects for decommissioned and existing power plants. In particular, the poor economic viability of small hydropower and the time-consuming implementation of projects are slowing down additional construction.
The scope for building new hydropower is limited, in particular for environmental and nature conservation reasons, which may also limit the use of existing capacity. Finland’s 2019 Government Programme included an update of the Water Act, which extended the fisheries obligations of the Water Act to so-called zero discharge installations. This tightens the environmental obligations for small hydropower and also partly changes the profitability of small hydropower.
Environmental impact
The adverse environmental impacts of small hydropower are particularly severe on stream habitat types, many of which are threatened. Abrupt fluctuations or stagnation of flows are detrimental to, for example, salmon fry, mussels and stream ecosystems in general. Missing or poorly constructed fish ladders can prevent migratory fish from reaching their spawning grounds. Dams and fluctuating flows also hamper recreational use of rivers.
The environment for small hydro has changed considerably over the last decade. The environmental impact of additional hydropower development has been the subject of much debate. The development of additional small hydropower has become more critical as information on the environmental impacts has increased.
Small hydropower operations have also been closed down in recent years or will be closed down in the near future in various parts of Finland, such as Kirakkaköngäs in Inari, Hiitolanjoki power plants in North Karelia, Tourujoki power plant in Jyväskylä and Louhikoski power plant in Nurmes.
State aid is also available for the decommissioning of a small hydropower plant. One of the objectives of the Ministry of Agriculture and Forestry’s NOUSU programme is to dismantle fish migration barriers and promote projects to decommission small hydropower.
Elsewhere online:
Association for Small Water Power
The NOUSU programme to recover migratory fish stocks (MMM)
Hydropower (Energy Industry Association)
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Milja Aarni
Expert