Cray Reservoir is a storage

reservoir A reservoir (; from French ''réservoir'' ) is an enlarged lake behind a dam. Such a dam may be either artificial, built to store fresh water or it may be a natural formation. Reservoirs can be created in a number of ways, including contro ...

located in the

Brecon Beacons National Park The Brecon Beacons National Park ( cy, Parc Cenedlaethol Bannau Brycheiniog) is one of three national parks in Wales, and is centred on the Brecon Beacons range of hills in southern Wales. It includes the Black Mountain ( cy, Y Mynydd Du) i ...

(named after the village of Crai) for the

water supply Water supply is the provision of water by public utilities, commercial organisations, community endeavors or by individuals, usually via a system of pumps and pipes. Public water supply systems are crucial to properly functioning societies. Thes ...

to the city of Swansea in South Wales and was built between 1898 and 1908 by Swansea Corporation. The reservoir now supplies water to the towns in the valley of the

River Tawe The River Tawe (; cy, Afon Tawe ) is a long river in South Wales. Its headwaters flow initially east from its source below Llyn y Fan Fawr south of Moel Feity in the Black Mountains, the westernmost range of the Brecon Beacons National ...

and north Swansea. The reservoir is one of several established in what is now the Brecon Beacons National Park, an area of

Old Red Sandstone The Old Red Sandstone is an assemblage of rocks in the North Atlantic region largely of Devonian age. It extends in the east across Great Britain, Ireland and Norway, and in the west along the northeastern seaboard of North America. It also exte ...

peaks with relatively high

rainfall Rain is water droplets that have condensed from atmospheric water vapor and then fall under gravity. Rain is a major component of the water cycle and is responsible for depositing most of the fresh water on the Earth. It provides water f ...

. The 28-metre high dam is within a wide

glaciated valley U-shaped valleys, also called trough valleys or glacial troughs, are formed by the process of glaciation. They are characteristic of mountain glaciation in particular. They have a characteristic U shape in cross-section, with steep, straight s ...

and is estimated to impound some 1,007,000,000 gallons of water. The structure is believed to have been made from over 10 million bricks. Upstream of Cray Reservoir the land is largely upland moorlands or unimproved grassland with one area now given over to coniferous forestry. The impounded water quality is good and the water requires only minimal treatment before entering the

water supply system A water supply network or water supply system is a system of engineered hydrologic and hydraulic components that provide water supply. A water supply system typically includes the following: # A drainage basin (see water purification – sourc ...

. The treatment of screening, disinfection and lime dosing is carried out south of the reservoir at Nant yr Wydd. Despite the generally excellent quality of the water, there have been occasional episodes of impaired quality mostly concerned with forestry planting and the release of difficult to treat turbidity into the reservoir. On occasions when such raw water quality impairment has overwhelmed the treatment facilities, some bacteriological deterioration has been experienced in the downstream water supply system such as in 1981.Water Supply and Forestry, a conflict of Interests - Cray Reservoir - a case study - C Stretton
/ref> Plaque on the Dam Crest .jpg, Plaque Face of the Dam.jpg, Face of the dam

References

External links

www.geograph.co.uk : photos of Cray Reservoir and surrounding area
{{authority control Cray, Powys Fforest Fawr Reservoirs in the Brecon Beacons National Park Reservoirs in Powys