Loch Mhor begins at the village of Errogie. It was made when two separate lochs – Loch Farraline and Loch Garth were joined. Loch Mhor lies 180 metres above Loch Ness.The Loch is part of the Hydro-Electric Power Scheme located in Foyers.

The Loch is connected via the Foyers pumping station to Loch Ness by pipes and tunnels and during the day when the demand for electricity is high water is dropped down from Loch Mhor to Loch Ness generating power in the process.

At night when the demand for electricity is low the water is pumped back into Loch Mhor to be used again the next day.