1. Reservoir is retained by Caban Coch Dam (nprn 261521) and bounded by Garreg-ddu submerged dam (nprn 752); lowest level of the Elan Valley Water Scheme (nprn 96459). The water above the level of Garreg-ddu submerged dam is used for supply and that below the level is used only for river compensation.
B.A.Malaws, RCAHMW, 21 November 2003.

2. Construction began in 1893. Total capacity - 35,500 megalitres; Top water level above OS Datum - 250m; Height of dam above river bed - 37m; Length of dam - 186m; Thickness at base - 38m (RSJ 2000).