How is biodiversity affected by the implementation of environmental flows in regulated watercourses?
The purpose of this research summary is to investigate the effect of more naturally regulated flows from hydropower dams on biodiversity. This knowledge is relevant to the environmental objectives of Rich plant and animal life and Living lakes and rivers.
Ongoing research synthesis. The report is expected to be completed in 2026.
Background information
There are several thousand dams in Sweden, of which only a few hundred account for the overwhelming majority of total hydropower production. Other dams are often smaller facilities, adapted for small-scale power generation. They may be former mills or factories, or they may generate electricity for small towns.
As the dams were often built a long time ago, the conditions for them have in many cases not been tested against current environmental legislation, which includes both the Environmental Code and the EU Water Framework Directive. Therefore, the government has decided on a national plan to review the permits for hydropower plants and dams. Hydropower is of great importance for the transition to a fully renewable electricity system, and the goal is therefore the greatest possible benefit for the aquatic environment and at the same time an efficient supply of hydropower electricity.
As part of the assessment process, hydropower plants may need to be environmentally adapted. This can be done in different ways. One possible measure is to regulate the flows from the dams so that they become more natural, through so-called environmental or ecological flows. This can promote biodiversity. However, the extent of the effects is unclear, both near the dams and in the catchment.
Methods
We compile the research in the field in the form of a systematic review. The aim of systematic reviews is to provide the most reliable answer possible to a well-defined question, based on all the research available on the issue. This requires an approach that is systematic, objective and transparent. We follow the guidelines for systematic reviews in the environmental field developed by the international organization Collaboration for Environmental Evidence. To ensure high scientific quality, we have engaged a group of expert researchers in the project. These scientists are responsible for the scientific assessment and analysis. You can read more about the process here.
Together with the researchers and stakeholders, i.e. representatives from authorities and interest groups, we have developed an implementation plan. In it, we describe the methods we will use and the delimitations we will make. The implementation plan will be reviewed by external experts. Once the systematic review is completed, it will also be reviewed by external experts. The report is expected to be completed in 2026 and will then be published here on Formas' website.
A systematic review protocol: How is biodiversity affected by the implementation of environmental flows in regulated watercourses?
Formas report number: G4:2025
ISBN: 978-91-540-6245-4
DOI: https://doi.org/10.65059/formas2025.003 External link.
Language: English
License: https://creativecommons.org/licenses/by/4.0/ External link.
Project group
Expert researchers
- Roland Jansson, Umeå University (chair of the expert group)
- Peter Carlson, Swedish University of Agricultural Sciences, SLU
- Birgitta Malm-Renöfält, Umeå University
- Saija Koljonen, SYKE, Finland
From Formas
- Josefin Thorslund, project manager
- Arvid Bring, Deputy Project Manager
- Matilda Svensson, Information Specialist
- Henrik Scharin, Economist