National
Auchengaich Reservoir was created in 1942 through the construction of an earthfill dam built by the military to supply water to Helensburgh and the Gareloch during World War II.RCAHMS Canmore - Auchengaich Reservoir.
See also List of reservoirs and dams in the United Kingdom
Sources
"Argyll and Bute Council Reservoirs Act 1975 Public Register"