It contains 900,000 cubic metres (200,000,000 imp gal) of water received from the Elan Valley Reservoirs,[2] 117 km (73 mi) away, in Wales, which arrives via the Elan aqueduct, by the power of gravity alone, dropping 52 metres (171 ft) – an average gradient of 1 in 2,300.
Before 1987 it was leaking 540 litres (120 imp gal) per second. In that year ground-penetrating radar was used successfully to isolate the leaks.[2]
^Environment Agency public register of Large Raised Reservoirs, as at 2 November 2020, via Boswarva, Owen. "Large Raised Reservoirs". Retrieved 7 December 2020.
^ abc"Radar". Penguin Dictionary of Civil Engineering. Penguin Books. p. 347.