Mitigation requirements for hydropower plants

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Mitigation requirements for hydropower plants

When planning mitigation measures for new or existing hydropower plants, the mitigation requirements based on legislation, other types of recommendations (e.g. guidelines or technical standards) or decisions by permitting authorities need to be reviewed and taken into account.

Mitigation requirements for hydropower plants can be distinguished for the following key domains of environmental improvements at hydropower plants:

  • upstream fish migration,
  • downstream fish migration,
  • flow conditions,
  • hydropeaking,
  • gravel transport (sediment), and
  • habitat enhancement.

This page cannot give a comprehensive picture of mitigation requirements for hydropower plants in the EU. You may refer to the FIThydro report “Deliverable 5.1. Review of policy requirements and financing instruments” for a review of mitigation requirements in eight European countries (Spain, Portugal, France, Austria, Germany, Switzerland, Sweden, Norway) with some examples provided below.

The impacts from disrupted upstream fish migration and modified flow conditions are the ones most commonly required by legislation to be mitigated. Requirements to mitigate modified flow conditions usually refer to minimum flow requirements and, in different countries, different methods are used for determining minimum flow (Kampa et al., 2017).

In some countries, there are no mitigation requirements related to gravel transport (sediment), hydropeaking impacts and downstream fish migration, mainly due to still open questions which need clarification through further research or pilot studies. For these types of impacts, several countries follow a case-by-case approach when defining mitigation requirements (Kampa et al., 2017).

Requirements for mitigation Selected examples from European countries
Upstream fish migration Germany: the federal States have specific technical and hydraulic requirements for upstream fish migration measures.
Austria; ensuring ecological continuity is compulsory except outside of the natural fish zone and very near to natural existing barriers.
Switzerland: HPP (new and existing ones) are required to mitigate interrupted fish migration by 2030
Downstream fish migration Germany: some federal states indicate in specifications on fish protection (e.g. protection screens) in their federal laws.
Austria: as there as is no proven state-of-art-technology to ensure downstream migration, there is no general requirement (only some pilot facilities).
Norway: requirements related to downstream migration have historically been an issue only to a limited extent, and have received less
attention than upstream migration. However, there is growing concern that this is a key issue which also requires mitigation.
Flow conditions Germany: the amount of minimum flow is aligned with management objectives according to the WFD (according to law WHG §§ 27-31).
France: maintenance of minimum flow is an obligation since 2006 with the requirement to implement minimum flow values by 2014.
Spain: minimum flows were to be implemented in the river basin management plans, generally before 2015, on a case by case basis. A basic legal
framework for ecological flows exists and many licenses include requirements concerning minimum flows. Depending on specific conditions, new
minimum flow requirements for existing plants may be determined on case by case.
Hydro-peaking Switzerland: hydropeaking needs to be mitigated by 2030. Structural or operational measures can be applied.
Austria: Due to still open questions, implementation of mitigation measures was postponed to WFD cycle after 2021. Hydropower companies have to
provide feasibility studies for their hydropeaking plants until 2021 on how hydropeaking can be mitigated effectively.
Norway: requirements on hydropeaking operations have been defined in only very few cases so far (some producers introduced voluntary restriction
on such operations in some cases).
Gravel transport (sediment) Austria: a national ordinance (mainly applicable to new HPP) states that good ecological status can be achieved with high confidence if sediment
dynamics is only modified within short river stretches.
Switzerland: mitigation of gravel transport is required by 2030.
Germany, Portugal, France: requirements for mitigating gravel transport are assessed on a case-by-case basis.
Habitat enhancement Switzerland: revitalization and improvement of morphology is required by 2090.
Germany: habitat improvements are indirectly required via the provisions of the WFD.
Austria: there is a requirement to minimise impacts as far as possible for new plants and to achieve good status/potential, which means that morphological
mitigation measures have to be implemented. Existing HPP with an impoundment are usually designated as heavily modified and the definition of GEP
includes morphological improvements.

Source: Kampa et al. (2017).

Literature cited

  • Kampa et al. (2017), FIThydro Deliverable 5.1. Review of policy requirements and financing instruments.