As energy firms race to meet challenges of storing power, critics worry about fluctuations in the depth of the loch.

Brian Shaw stood at the edge of Loch Ness and pointed to a band of glistening pebbles and damp sand skirting the shore. It seemed as if the tide had gone out.

Overnight, Foyers, a small pumped-storage power station, had recharged itself, drawing up millions of litres of water into a reservoir high up on a hill behind it, ready for release through its turbines to boost the UK’s electricity supply. That led to the surface of Loch Ness, the largest body of freshwater in the UK, falling by 14cm in a matter of hours.

Shaw, an expert in freshwater salmon who runs the Ness District Salmon Fishery Board, believes this is a warning of things to come. “I had a complaint about the level of Loch Ness dropping by a foot overnight,” he said, gesturing at the shore. “It’s actually dropped six inches over the course of the day. That wouldn’t happen naturally.”

Foyers power station was built in 1974, and after a 40-year absence, pumped hydro storage is back on the agenda and with it fresh questions about who the water belongs to.

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