It occupies an area known as Deers Meadow, and impounds the River Bann, which rises on the nearby Slieve Muck.

The reservoir and dam were built as part of a project that had origins in the idea of supplying water to Belfast, in 1894.

[1] The Dam was designed by the Belfast engineering firm of R. Ferguson and S. McIlveen and construction was undertaken by John Laing & Sons.

[2][3] Prior to the construction of the reservoir, archaeological excavation was carried out and three groups of transhumant buildings, or booley huts, were identified.

Some of the structures were dated to the eighteenth century, but it is thought that the site had been used since pre-historic times due to the presence of flint flakes.