Cray reservoir
Encyclopedia
Cray Reservoir is a storage reservoir
located in the Brecon Beacons National Park for the water supply
to the city of Swansea
in South Wales
and was built between 1898 and 1906 by Swansea Corporation.
The reservoir now supplies water to the towns in the valley of the River Tawe
and north Swansea.
The location of the reservoir was chosen as it was upstream of the heavily industrialised parts of the Tawe valley and in an area of high rainfall with as large an upstream catchment as possible. This meant that the ideal location was just to the north of the carboniferous
coal
belt on the Old Red Sandstone
within the Brecon Beacons National Park. The 28-metre high dam is at the lower end of a wide glaciated valley and is estimated to impound some 4.5 million tonnes of water.
Upstream of Cray Reservoir the land is largely upland
moorland
s or unimproved grassland with large areas now given over to plantings of conifers. The impounded water quality is therefore good and the water requires only minimal treatment before entering the water supply system. 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. http://www.strettonassociates.com/publications/craipaper.htm
Reservoir
A reservoir , artificial lake or dam is used to store water.Reservoirs may be created in river valleys by the construction of a dam or may be built by excavation in the ground or by conventional construction techniques such as brickwork or cast concrete.The term reservoir may also be used to...
located in the Brecon Beacons National Park for the water supply
Water supply
Water supply is the provision of water by public utilities, commercial organisations, community endeavours or by individuals, usually via a system of pumps and pipes...
to the city of Swansea
Swansea
Swansea is a coastal city and county in Wales. Swansea is in the historic county boundaries of Glamorgan. Situated on the sandy South West Wales coast, the county area includes the Gower Peninsula and the Lliw uplands...
in South Wales
South Wales
South Wales is an area of Wales bordered by England and the Bristol Channel to the east and south, and Mid Wales and West Wales to the north and west. The most densely populated region in the south-west of the United Kingdom, it is home to around 2.1 million people and includes the capital city of...
and was built between 1898 and 1906 by Swansea Corporation.
The reservoir now supplies water to the towns in the valley of the River Tawe
River Tawe
The River Tawe is a river in South Wales. It flows in a principally south-westerly direction for some from its source below Moel Feity in the Old Red Sandstone hills of the western Brecon Beacons to the Bristol Channel at Swansea. Its main tributaries are the right bank Upper and Lower Clydach...
and north Swansea.
The location of the reservoir was chosen as it was upstream of the heavily industrialised parts of the Tawe valley and in an area of high rainfall with as large an upstream catchment as possible. This meant that the ideal location was just to the north of the carboniferous
Carboniferous
The Carboniferous is a geologic period and system that extends from the end of the Devonian Period, about 359.2 ± 2.5 Mya , to the beginning of the Permian Period, about 299.0 ± 0.8 Mya . The name is derived from the Latin word for coal, carbo. Carboniferous means "coal-bearing"...
coal
Coal
Coal is a combustible black or brownish-black sedimentary rock usually occurring in rock strata in layers or veins called coal beds or coal seams. The harder forms, such as anthracite coal, can be regarded as metamorphic rock because of later exposure to elevated temperature and pressure...
belt on the Old Red Sandstone
Old Red Sandstone
The Old Red Sandstone is a British rock formation of considerable importance to early paleontology. For convenience the short version of the term, 'ORS' is often used in literature on the subject.-Sedimentology:...
within the Brecon Beacons National Park. The 28-metre high dam is at the lower end of a wide glaciated valley and is estimated to impound some 4.5 million tonnes of water.
Upstream of Cray Reservoir the land is largely upland
Highland (geography)
The term highland or upland is used to denote any mountainous region or elevated mountainous plateau. Generally speaking, the term upland tends to be used for ranges of hills, typically up to 500-600m, and highland for ranges of low mountains.The Scottish Highlands refers to the mountainous...
moorland
Moorland
Moorland or moor is a type of habitat, in the temperate grasslands, savannas, and shrublands biome, found in upland areas, characterised by low-growing vegetation on acidic soils and heavy fog...
s or unimproved grassland with large areas now given over to plantings of conifers. The impounded water quality is therefore good and the water requires only minimal treatment before entering the water supply system. 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. http://www.strettonassociates.com/publications/craipaper.htm