The preglacial col in the former divide at Beinn Bheoil - Stob an Aonaich Mhoir is estimated by Linton to have been at 650m asl.

A secondary breach was cut between The Fara (Am Faireamh) and Geal Charn (Drumochter) thus beheading the Pattack catchment.

The present watershed has been displaced about ten miles north-east to Dalwhinnie [6] The loch is part of a hydro-electric scheme and is dammed at both ends.

The southern end is linked to a hydro-electric power station at Loch Rannoch by a pipeline abstracting most of the flow of the 4-mile (6.4 km) long River Ericht.

[7] The Corrievarkie pumped-storage hydroelectricity project is planned to hold 22 million cubic metres of water in the hills above the lake.