A map showing where hydropower could be used in England and Wales could help to tap into the unused power potential of British rivers, according to the Environment Agency.

The hydropower opportunities and environmental sensitivities map, commissioned by the agency, found almost 26,000 locations where a hydropower turbine could theoretically generate green electricity.

Together, these sites could generate enough electricity to power up to around 850,000 homes and produce 3% of the country's 2020 renewable electricity needs.

However, in reality, however, only some of these sites could be exploited due to environmental sensitivities, as well as practical constraints such as access to the electricity network.

Tony Grayling, head of climate change and sustainable development at the environment agency said: "Some hydropower schemes have the potential to deliver low carbon electricity and improve the local environment for wildlife, for example by improving fish migration.

"But there will inevitably be some sites where the risk to the environment outweighs the benefits of power generation.

"With Government's new feed-in tariff for renewably generated electricity, hydropower could become an attractive income generator for hydropower developers, if environmental safeguards are met.

"The report recommends that fish-friendly design needs to be incorporated in all schemes, and that grants for fish passes could help to unlock the potential of small scale hydropower in England and Wales."

The full report Opportunity and environmental sensitivity mapping in England and Wales , and the interactive hydropower maps are available online from the agency.

Luke Walsh