The Loch Ness scheme would shunt so much water up and down the surrounding hills that levels could rise and fall by 60-90cm a day. Critics say this would wreck its ecology.
Brian Shaw, the chief executive of the Ness District Salmon Fishery Board, said: “It’s absolutely crazy to have a world-renowned, iconic lake like Loch Ness subject to these harmful schemes. It will turn it into a tidal lake, damaging the shoreline ecology with the plumes of turbulent water from the pipes, damaging the water quality.”
A separate dam scheme is planned for Earba, near Dalwhinnie, on the Ardverikie Estate, whose stately home was used for filming TV series, including The Crown and Monarch of the Glen.
The project would build a 110m-high dam built, turning a rare twin loch – adjacent Ice Age lakes – into a single massive reservoir.
The third hydropower scheme promoted by Miliband is in development on the shores of Loch Lochy in the Scottish Highlands between Fort William and Inverness.
All three are so-called “long-duration” power storage projects that can store and unleash power when needed. Ofgem has shortlisted a total of 16 such projects for support, of which 12 involve building massive banks of batteries. Another scheme would store energy as compressed air in a massive underground salt cavern.
The provisional green light has been granted as Britain’s power network comes under pressure from an intense heatwave, which has forced authorities to seek extra power from abroad at excessively high prices.
Energy Minister Michael Shanks said: “Britain cannot afford to remain at the mercy of volatile fossil fuel markets. We are rolling out a new generation of pumped hydro storage and state-of-the-art batteries – making more of the clean, homegrown power we already produce.”
Tom Vernon, the chief executive of Statera Energy, said the support for the Loch Ness project was “a strong vote of confidence in the role Statera’s projects can play in accelerating UK flexibility”.
Kate Gilmartin, of the British Hydropower Association, a trade body, welcomed Ofgem’s announcement and said the projects could benefit today’s consumers as well as future generations.
However, she added: “These schemes are major civil engineering projects, and it would be wrong to pretend they have no impact. They must be assessed rigorously … The test should be: is the impact understood, minimised, mitigated and outweighed by the long-term public benefit?”
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