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Galloway Hydroelectric Scheme
Dumfries & Galloway and Ayrshire, Scotland, UK
Galloway Hydroelectric Scheme
associated engineer
Sir Alexander Gibb & Partners
Merz & McLellan
date  1931 - 1937, 1985
era  Modern  |  category  Power Generation  |  reference  NX605805
ICE reference number  HEW 1457
photo  © and licensed for reuse under this
The Galloway Water Power Scheme, as it was first called, was set up in order to generate electricity for the south west Scotland regional grid. These days it includes six hydroeclectric power stations, eight dams, a barrage, seven reservoirs and a network of tunnels, aqueducts and pipelines. Its catchment area is 103,600 hectares of Dumfries & Galloway and south Ayrshire.
The idea of generating hydroelectric power in Galloway was first suggested in the late 19th century, but it wasn't until 1923 that Colonel William McLellan (1874-1934) was appointed consulting engineer, responsible for "imagining, conceiving, and directing the construction of the great work".
On 10th May 1929, the Galloway Water Power Act was passed by Parliament. It was the last day of Stanley Baldwin’s (1867-1947) Labour Government. To develop the £3m scheme, the Galloway Water Power Company was set up, and Sir Alexander Gibb & Partners and Merz & McLellan were jointly commissioned to design the power station network and all the necessary infrastructure. Construction began in 1931, and work proceeded in two stages until completion in 1937. At its peak, the project employed 1,500 people.
The Galloway scheme was designed from the start to handle peak loads — it was not intended to be in continuous operation. The idea is to improve the load factors of other power stations in mid Scotland and northern England. The exception to this is when the supply rivers are in flood. The annual output of the scheme is low in comparison with the installed plant capacity. The maximum output was planned to be 102MW, which was achieved and later exceeded.
The project’s catchment area has a length of about 58km and a maximum width of some 30km, reaching almost to the sea at Kircudbright and extending northwards to the hills south of Dalmellington. The major part of it is drained by two rivers, the Galloway Dee and the Water of Ken, together with their tributaries. A subsidiary portion of the catchment includes the River Doon, which is collected in Loch Doon and diverted by tunnel into the Dee.
The size of the area and the general tendency of the ground to slope to the south did not allow the water to be gathered into a single reservoir. Instead, five power stations were constructed that used the flow of water in individual valleys, with the lowest one (Tongland) alone taking water from the whole catchment.
The five stations are, in descending order: Kendoon, Carsfad, Earlstoun, Glenlee (pictured and mapped) and Tongland. All the power station substructures were constructed in reinforced concrete inside the main buildings’ steel frames, and exhibit faithfully the Modernist engineering architecture of the 1930s. During World War II (1939-45) the stations were painted in camouflage colours, instead of their usual creamy white, to prevent detection by enemy aircraft.
All the power stations, except for Glenlee, were planned to be in operation for 5-8 hours out of 24 (except during floods), mainly using water from Loch Doon. Glenlee is on a separate arm of the scheme and draws water from Clatteringshaws Reservoir through a tunnel 5.8km long and 3.35m in diameter.
Glenlee power station was commissioned in March 1935 and has a maximum output capacity of 24MW for an average net head of 116m. Tongland was commissioned in May 1935, with a capacity of 33MW at a head of 32m. The other three stations were commissioned in 1936 — Kendoon has a capacity of 24MW at a head of 46m, Earlstoun 14MW at 20m and the last Carsfad, commissioned in October 1936, generates 12MW at a 20m head.
Substations were built at Kendoon, Glenlee and Tongland to step up the electricity generated at the power stations from 11kV to 132kV. This was then transmitted to the electricity grid via a power line from Galloway to Carlisle.
Dams were required at Loch Doon, Water of Deugh, Water of Ken, Loch Whinnie, Carsfad, Earlstoun, Clatteringshaws and Tongland. There are eight in all, plus the Glenlochar Barrage on Loch Ken. The three downstream structures — the Glenlochar Barrage, Tongland Dam and Clatteringshaws Dam — were finished in 1934 and the remaining five dams were completed in 1937.
Loch Doon and Clatteringshaws Reservoir are the largest water impounds, with capacities of 82.5 and 35.4 million cu m of water respectively. They are used for seasonal storage in that they are depleted in spring and summer, and replenished in winter. The reservoirs at Kendoon, Carsfad, Earlstoun and Tongland are used for daily storage, while Loch Ken provides medium-term storage and a buffer for Tongland Power Station.
Several pipeline intakes, tunnels and aqueducts were required as well, totalling more than 12km in length. Surge towers were built at Tongland and Kendoon to protect the aqueducts in the case of sudden power station shut down.
The damming of Loch Doon rasied its water level by some 8m, endangering the 13th century castle that stood on an islet in the southern half of the loch. Loch Doon Castle has an eleven-sided curtain wall, and was built by the Bruce Earls of Carrick. It was abandoned in the 17th century. To avoid its loss, in 1935 it was dismantled and re-erected about half a kilometre north west of its original site. The remains of its foundations may be seen in the loch during low water.
The Rivers Dee, Ken and Doon are salmon and sea trout rivers, so fish passes had to be constructed at the Tongland, Earlstoun, Carsfad and Loch Doon dams to allow migratory fish to make their way upstream from the sea to spawning grounds.
A small sixth power station was added at the top of the project, at Drumjohn, in 1985 to exploit the power of water passing through a needle valve there. It has a capacity of 2.25MW at an average net head of 13m.
The scheme is owned and operated by Scottish Power. It now has a total capacity of109.25MW. In 2009 the scheme generated 260 GWh of electricity.
Contractors: A.M. Carmichael Ltd, John Howard & Co Ltd, Shanks McEwan Ltd, Sir Robert McAlpine & Sons Ltd and Sir William Arrol & Co Ltd
Generating machinery: English Electric Company Ltd
Research: ECPK
bibliography
"Discussion on Galloway Hydro-Electric Development" by J.K. Hunter et al
in Journal of the ICE, Vol.8, pp.423-454, London, April 1938
"Galloway Hydro-Electric Scheme" information leaflet available at www.scottishpower.com
"Galloway Hydros” series of factsheets available at www.spenergywholesale.com
www.historic-scotland.gov.uk
reference sources   CEH SLB
Location

Galloway Hydroelectric Scheme