1. Pen-y-garreg Reservoir is the middle level of the Elan Valley Water Scheme (nprn 96459), and was created by construction of Pen-y-garreg Dam (nprn 32534).
B.A.Malaws, 21 November 2003.

2. Built between 1893-1904. Engineer James Mansergh. Bronze plaque gives measurements in Imperial. Total capacity - 6,055 megalitres; Top water level above OS Datum - 288m; Height of dam above river bed - 37m; Length of dam - 161m.(RSJ 2000)