Impacts of Hydropower

Some impacts to habitat and fish migration by the more than 1,000 hydropower dams licensed by the Federal Energy Regulatory Commission (FERC) include:

• Migration blockage—Hydropower dams block the continuous flow of rivers and streams. As fish attempt to move up and down rivers, hydropower dams physically block their movement. In some cases it is possible to build passages that allow fish to migrate upstream around a dam.
• Habitat changes—Hydropower facilities can change water volume, temperature, depth, and velocity, and alter dissolved oxygen sediment loads.
• Turbine strike—Even if fish can migrate upstream past a dam, they can suffer injury or death during their downstream migration if they come in contact with a dam’s turbines.
• Fish become prey—Hydropower dams might attract predatory species because of increased concentration of fish due to migratory delays, disoriented or injured fish from turbine strikes, or predator-friendly habitat.