3.2.3 Hydropower

3.2.3 Hydropower

Overview

Hydropower has a long history in Europe and currently generates around 10 % of the European net electricity (Eurostat, 2019) and more than one third of renewable electricity in EU (in 2015, based on Eurelectric & VGB Powertech (2018)). Norway and Switzerland are also countries with especially high importance of hydropower. At the same time, the construction and operation of hydropower plants causes major impacts on water bodies and adjacent wetlands, such as changes in the flow regime and sediment transport, loss of key habitats and river fragmentation.

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In the second RBMPs, 22 WFD countries reported significant pressures in the form of barriers, hydrological alterations and abstractions related to hydropower production, affecting approximately 9 000 surface water bodies (6 % of total water bodies). In addition, hydropower is the most common water use for designating heavily modified water bodies, related to ca. 6 000 heavily modified water bodies in 25 WFD countries (half of these water bodies are in Norway).

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In Europe, currently more than 21 000 hydropower plants exist. The majority (ca. 90 %) are hydropower plants smaller than 10 MW installed capacity (WWF, 2019). Large hydropower plants (more than 10 MW) represent only 10 % of all hydropower facilities but they generate almost 90 % of the total hydropower energy production (Devoldere et al., 2011). Germany has the highest number of hydropower plants (more than 7 700), while Austria, France, Italy, and Sweden all have more than 2 000 hydropower plants (Kampa et al., 2011). Also, in Norway and Spain, there are more than 1 000 existing hydropower plants (WWF, 2019).

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Figure 9             Recorded hydropower plants in Europe 

Notes: Left, Distribution of hydropower plants; Right, Distribution of hydropower plants by status and size class.

Source: WWF, 2019

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The main types of hydropower plants based on the ability to store water are 1) run-of-river, 2) storage and 3) pumped storage plants. Run-of-river plants are plants without reservoirs, which run on the natural discharge of the river. Storage plants require the construction of a dam and a reservoir to store water. In many regions of Europe, run-of-river plants are the most common type of hydropower plants, but storage and pumped storage plants account for a higher share of the installed capacity.

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Figure 11           Images of small hydropower plant (left) and large hydropower plants, storage and run-of-river (centre and right)

 Photos not shown    

Notes: Insert notes here

Sources: 1) By Tangopaso - Own work, Public Domain, https://commons.wikimedia.org/w/index.php?curid=23481491, 2) https://vaw.ethz.ch/en/research/hydraulic-engineering/ethohydraulics.html, 3) https://upload.wikimedia.org/wikipedia/commons/f/fe/Altakraftverket%2C_Norge.jpg

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The largest development of hydropower in Europe took place over the last century, harnessing most of the large hydropower potential on the continent. Nonetheless, new hydropower plants are still under development. Several hydropower plants in Europe are under construction (278) and many more are planned to be constructed (8 507). Especially, the Balkans and Turkey have ambitious plans to significantly raise their hydropower exploitation (WWF, 2019). Also, in other parts of Europe, there is an increasing number of applications for new hydropower plants, especially small ones up to 10 MW. For example, in Italy, there are more than 500 requests for new hydropower plants of 1 MW and in Scotland, there have been more than 700 applications for new hydropower development in the last 15 years (Bussettini, 2019; Fyfe, 2019). 

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Impacts

Hydropower generation causes impacts on aquatic ecology, natural scenery, and ecosystems. The possible key ecological impacts of hydropower are described below (based on ICPDR, 2013).

Hydropower dams and weirs cause an interruption of the longitudinal river continuity. Migrating fish species such as the eel and salmon are particularly affected by the fragmentation of their habitats. In addition, when fish pass through hydropower turbines as they move river downstream, a high proportion of them are injured or killed. The impact of acting as migration barriers is common to most types of hydropower plants.

Furthermore, hydropower plants change river hydromorphology. Hydrological processes and sediment transport lose their natural dynamics leading to altered natural structures and habitats.

Hydropower plants change the river flow regime. In rivers which are impounded for hydropower (typical for storage hydropower plants), flow velocity is reduced which can lead to the loss of orientation of fish. Reduced flow velocity results in other negative impacts such as increased deposition of fine sediment in the impoundment.

Another impact from hydropower results from rapidly changing flows called hydropeaking, which is mainly typical for large hydropower plants in combination with reservoirs. Hydropeaking can cause severe morphological and ecological effects on a river and particularly on fish populations.

Often, at run-of-river hydropower plants, a portion of the river water is diverted e.g. through a canal, to produce energy. This leads to large flow reductions immediately downstream of the river diversion as well as changes in flow patterns further downstream.

Water storage and river regulation through hydropower plants often also alter physical and/or chemical conditions downstream, with changes to water temperature, super saturation of oxygen and altered patterns of ice formation in winter.

Hydropower plants and dams are often not standing alone in a river system, but several can be present on the main river as well as on tributaries. The cumulative effects of multiple hydropower plants, in combination with barriers that do not serve electricity generation, need to be considered (Kampa & Berg, 2020). In a chain of impoundments containing several hydropower plants, the sum total of effects can endanger whole fish populations in a river basin.

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Measures and management challenges

In several countries, measures are being implemented to mitigate the impacts of hydropower plants on water bodies. The main measures are targeting upstream fish migration (especially fishways), downstream fish migration (e.g. fish guidance systems and bypasses, fish-friendly turbines), habitat restoration, sediment management as well as the implementation of ecological flows.

Most EU countries have relevant legislation in place to ensure minimum ecological flows and upstream continuity via fishways at hydropower plants. Legislative requirements though are largely missing to address other types of hydropower impacts, such as on downstream fish migration, sediment transport and hydropeaking because of still open questions that need to be addressed by research (Kampa et al., 2011).

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Hydropower plants generally operate under a permit/licensing scheme, whereby conditions for the operation are set. However, many hydropower plants were licensed prior to the adoption of key EU water policy such as the WFD in 2000 and national laws protecting rivers. In addition, in many countries, licenses are of unlimited or very long duration (e.g. up to 100 years). The large number of such licenses on old hydropower plants, whose operation conditions are difficult to change, remains a big challenge to the implementation of mitigation measures (Kampa et al., 2017).

Since 2000, the WFD has been a strong driver in modifying the licensing procedures for new hydropower plants and for revising licenses of existing plants in many countries. In case of new hydropower plants, licenses are issued which include requirements for implementing mitigation measures, to comply with national or regional mitigation requirements for hydropower plants.

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Also, reconstruction, repowering and application for subsidies is used for introducing ecological demands into the licences. There are plans to reconstruct many existing hydropower plants as a lot of facilities across Europe are more than 40 years old. The reconstruction and modernisation of old hydropower plants can often significantly increase power output and be an alternative to the construction of new plants that would impact further stretches of free-flowing rivers.

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Overall, as the energy systems of European countries depend on energy produced via hydropower, we need to find ways to implement measures that mitigate ecological impacts with the least possible effect on energy production for existing and new hydropower plants.

Large-scale strategies for more sustainable hydropower are being developed. Examples include Sweden’s new National Plan for the revision of hydropower licenses in the next 20 years, including a Hydroelectric Environmental Fund for mitigation measures based on industry contributions (SWAM, 2019). Switzerland’s Water Protection Act set mitigation targets for hydropower by 2030, offering financing of mitigation measures via an electricity surcharge (Kampa et al., 2017). Also, at transboundary level, Guiding Principles for Sustainable Hydropower Development have been developed for the international Danube Basin (ICPDR, 2013). At the same time, though, there is a worrying trend of development of many new hydropower plants especially in the Balkans and Turkey and a rising number of applications to develop small new hydropower plants across Europe.

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