Fish and aquatic biodiversity
The development of hydropower infrastructure is essential to address climate change, but should be managed in a way that mitigates impacts on local biodiversity.
As the largest renewable energy, making up more than half of global renewable energy production, sustainable hydropower is part of the solution to protecting the planet’s biosphere – and all life on Earth – by decarbonising the global economy, slowing the pace of climate change and preventing pollutants being emitted from fossil fuels.
Biodiversity impacts
The construction of a hydropower project will nonetheless inevitably have some impacts on the river system on which it is built, including on migratory fish and other species.
Identifying the extent of these impacts, and managing them responsibly, are among the most important priorities for hydropower developers and operators and crucial to local biodiversity conservation.
Mitigation hierarchy
The most common approach to managing biodiversity impacts from hydropower is by applying the mitigation hierarchy.
The mitigation hierarchy – avoid, minimise, mitigate and compensate – is a sequential process. First, a project should always seek to avoid or prevent negative or adverse impacts. For hydropower, this can include changes in site selection or project design to avoid the flooding of critical biodiversity areas.
When avoidance is not possible, projects should look to minimise adverse impacts. For example, a project can alter operational controls or implement environmental flows to minimise downstream impacts on river health. In cases where avoidance and minimisation are not practicable, projects should aim to mitigate and compensate the identified impacts. This can be done by restoring lost habitats and re-establishing biodiversity value to the affected area.
Practical measures
Hydropower developers and operators have deployed a range of practical measures to avoid or mitigate biodiversity impacts on fish and aquatic biodiversity. These include:
- Reservoir sediment and river erosion management
- Constructing fish passage facilities
- Modifying dam operations to restore river flows
- Building fish hatcheries
- Controlling the temperature and oxygen levels of water released from dams
- Conserving and remediating land surrounding reservoirs, rivers and dams
Case studies
• Hydro-Québec and Université du Québec en Outaouais study
• Canada’s award-winning ‘fish-first’ hydropower scheme
• Trevallyn hydropower project in Tasmania
• Global Hydropower Day 2023 - Fish Conservation
Good practice guidance
The Hydropower Sustainability Alliance addresses biodiversity conservation and provides guidance on good and best practices in hydropower development.
By assessing themselves against the requirements of the Biodiversity and Invasive Species guidelines and assessment criteria, hydropower projects can demonstrate their commitment to biodiversity in line with international standards.
Further reading
Read more about how sustainable hydropower can promote biodiversity.
Learn more about achieving and assessing good practice in biodiversity conservation.
