Crai Reservoir (also known as Cray Reservoir) is a storage

reservoir A reservoir (; ) is an enlarged lake behind a dam, usually built to water storage, store fresh water, often doubling for hydroelectric power generation. Reservoirs are created by controlling a watercourse that drains an existing body of wa ...

located in the

Brecon Beacons National Park Brecon Beacons National Park, officially named Bannau Brycheiniog National Park (), is a National parks of the United Kingdom, national park in Wales. It is named after the Brecon Beacons (), the mountain range at its centre. The national park ...

(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. Th ...

to the city of

Swansea Swansea ( ; ) is a coastal City status in the United Kingdom, city and the List of urban areas in the United Kingdom, second-largest city of Wales. It forms a Principal areas of Wales, principal area, officially known as the City and County of ...

South Wales South Wales ( ) is a Regions of Wales, loosely defined region of Wales bordered by England to the east and mid Wales to the north. Generally considered to include the Historic counties of Wales, historic counties of Glamorgan and Monmouthshire ( ...

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 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 Old Red Sandstone, abbreviated ORS, 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 eastern seaboard of North America. It ...

peaks with relatively high

rainfall Rain is a form of precipitation where water droplets that have condensed from atmospheric water vapor 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. ...

. The 28-metre high dam is within a wide glaciated valley 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 Crai Reservoir the land is largely upland

moorland Moorland or moor is a type of Habitat (ecology), habitat found in upland (geology), upland areas in temperate grasslands, savannas, and shrublands and the biomes of montane grasslands and shrublands, characterised by low-growing vegetation on So ...

s or unimproved grassland with one area now given over to

conifer Conifers () are a group of conifer cone, cone-bearing Spermatophyte, seed plants, a subset of gymnosperms. Scientifically, they make up the phylum, division Pinophyta (), also known as Coniferophyta () or Coniferae. The division contains a sin ...

ous 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