Carrigadrohid hydroelectric power station is a

hydroelectric plant Hydroelectricity, or hydroelectric power, is electricity generated from hydropower (water power). Hydropower supplies one sixth of the world's electricity, almost 4500 TWh in 2020, which is more than all other renewable sources combined and ...

located on the

River Lee The River Lee (Irish: ''An Laoi'') is a river in Ireland. It rises in the Shehy Mountains on the western border of County Cork and flows eastwards through Cork, where it splits in two for a short distance, creating an island on which Cork's ...

County Cork County Cork ( ga, Contae Chorcaí) is the largest and the southernmost county of Ireland, named after the city of Cork, the state's second-largest city. It is in the province of Munster and the Southern Region. Its largest market towns are ...

, Ireland. It is owned and operated by the

ESB Group The Electricity Supply Board (ESB; ga, Bord Soláthair an Leictreachais) is a state owned (95%; the rest are owned by employees) electricity company operating in the Republic of Ireland. While historically a monopoly, the ESB now operates as ...

. The dam is long and has a single

Kaplan turbine The Kaplan turbine is a propeller-type water turbine which has adjustable blades. It was developed in 1913 by Austrian professor Viktor Kaplan, who combined automatically adjusted propeller blades with automatically adjusted wicket gates to ach ...

which produces an average of each year. Built between 1952 and 1957. the construction of Carrigadrohid required the destruction of over half of

the Gearagh The Gearagh () is a submerged Glacial period, glacial woodland and nature reserve two kilometres southwest of Macroom, County Cork, in Kilmichael, County Cork, Kilmichael parish, Ireland. It is located at the point where the River Lee descends f ...

, an ancient alluvial forest, and initially harmed local wildlife. However, subsequently the area has seen the growth of an ecosystem with

kingfishers Kingfishers are a family, the Alcedinidae, of small to medium-sized, brightly colored birds in the order Coraciiformes. They have a cosmopolitan distribution, with most species found in the tropical regions of Africa, Asia, and Oceania, ...

otters Otters are carnivorous mammals in the subfamily Lutrinae. The 13 extant otter species are all semiaquatic, aquatic, or marine, with diets based on fish and invertebrates. Lutrinae is a branch of the Mustelidae family, which also includes wea ...

salmon Salmon () is the common name for several list of commercially important fish species, commercially important species of euryhaline ray-finned fish from the family (biology), family Salmonidae, which are native to tributary, tributaries of the ...

and

swans Swans are birds of the family Anatidae within the genus ''Cygnus''. The swans' closest relatives include the geese and ducks. Swans are grouped with the closely related geese in the subfamily Anserinae where they form the tribe Cygnini. Sometim ...

, which has been designated European Union

Special Area of Conservation A Special Area of Conservation (SAC) is defined in the European Union's Habitats Directive (92/43/EEC), also known as the ''Directive on the Conservation of Natural Habitats and of Wild Fauna and Flora''. They are to protect the 220 habitats and ap ...

Construction

The Carrigadrohid hydroelectric plant, along with its sister plant constructed downstream on the River Lee at

Inniscarra Inniscarra () is a civil parish in the barony of Muskerry East, County Cork, Ireland. It is located about 15km west of Cork city. The local GAA club is Inniscarra GAA and Dripsey GAA. Inniscarra is located on the north side of the River Lee. In ...

, formed the fourth major hydroelectric development undertaken by ESB. Construction of the reinforced concrete

gravity dam A gravity dam is a dam constructed from concrete or stone masonry and designed to hold back water by using only the weight of the material and its resistance against the foundation to oppose the horizontal pressure of water pushing against it. ...

started in 1952 and was complete in 1957. The dam is long and high, and operates with an average head of . It is constructed of nine blocks, each between in length, and is fitted with three ground sluices and a

spillway A spillway is a structure used to provide the controlled release of water downstream from a dam or levee, typically into the riverbed of the dammed river itself. In the United Kingdom, they may be known as overflow channels. Spillways ensure tha ...

weir.

Generating capacity

The plant consists of a single

rated at manufactured by

Voith The Voith Group is a German manufacturer of machines for the pulp and paper industry, technical equipment for hydropower plants and drive and braking systems. The family-owned company, which operates worldwide and has its headquarters in Hei ...

. It spins at 167 r.p.m. and feeds a single 11,500 kVA

Siemens Siemens AG ( ) is a German multinational conglomerate corporation and the largest industrial manufacturing company in Europe headquartered in Munich with branch offices abroad. The principal divisions of the corporation are ''Industry'', '' ...

generator running at 10.5 kV. The average output for the station is a year.

Impact on flooding

According to Cawley et al, the construction of this dam and the one at Inniscarra "have reduced significantly the extent and frequency of flooding along the Lee valley into Cork City". Prior to the construction, there were a number of fatal floodings in the city of

Cork Cork or CORK may refer to: Materials * Cork (material), an impermeable buoyant plant product ** Cork (plug), a cylindrical or conical object used to seal a container ***Wine cork Places Ireland * Cork (city) ** Metropolitan Cork, also known as G ...

, including one on 2 November 1853 that killed 12 people.

Impact on wildlife

As part of the construction of the reservoir to power the plant, 60% of

, an ancient alluvial forest, was flooded. The stocks of animals like

trout Trout are species of freshwater fish belonging to the genera '' Oncorhynchus'', ''Salmo'' and ''Salvelinus'', all of the subfamily Salmoninae of the family Salmonidae. The word ''trout'' is also used as part of the name of some non-salmoni ...

otter Otters are carnivorous mammals in the subfamily Lutrinae. The 13 extant otter species are all semiaquatic, aquatic, or marine, with diets based on fish and invertebrates. Lutrinae is a branch of the Mustelidae family, which also includes wea ...

eel Eels are ray-finned fish belonging to the order Anguilliformes (), which consists of eight suborders, 19 families, 111 genera, and about 800 species. Eels undergo considerable development from the early larval stage to the eventual adult stage ...

s and

freshwater pearl mussel The freshwater pearl mussel (''Margaritifera margaritifera'') is an endangered species of freshwater mussel, an aquatic bivalve mollusc in the family Margaritiferidae. Although the name "freshwater pearl mussel" is often used for this species ...

s were also negatively impacted by the construction. Many species, including freshwater pearl mussels,

Atlantic salmon The Atlantic salmon (''Salmo salar'') is a species of ray-finned fish in the family Salmonidae. It is the third largest of the Salmonidae, behind Siberian taimen and Pacific Chinook salmon, growing up to a meter in length. Atlantic salmon are ...

whooper swan The whooper swan ( /ˈhuːpə(ɹ) swɒn/) (''Cygnus cygnus''), also known as the common swan, pronounced ''hooper swan'', is a large northern hemisphere swan. It is the Eurasian counterpart of the North American trumpeter swan, and the type specie ...

common kingfisher The common kingfisher (''Alcedo atthis''), also known as the Eurasian kingfisher and river kingfisher, is a small kingfisher with seven subspecies recognized within its wide distribution across Eurasia and North Africa. It is resident in much of ...

s and

Eurasian otter The Eurasian otter (''Lutra lutra''), also known as the European otter, Eurasian river otter, common otter, and Old World otter, is a semiaquatic mammal native to Eurasia. The most widely distributed member of the otter subfamily (Lutrinae) of ...

s, can still be seen in the area and the reservoir has been designated a European Union

. There is a salmon hatchery where over a million smolts are reared every year, of which over 100,000 are released into the river.

References

{{Electricity generation in Ireland Hydroelectric power stations in the Republic of Ireland Gravity dams Dams completed in 1957