We own 7 impounding reservoirs, 4 of which are currently operational; West Baldwin, Sulby, Clypse and Kerrowdhoo. These reservoirs provide raw water to the Island's 2 water treatment works at Douglas and Sulby.

Cringle and Ballure Reservoirs are no longer used for drinking water supply and Block Eary Reservoir supplies water for hydroelectric power generation. Find out more about each reservoir below.

Image of Cringle Reservoir

Cringle Reservoir was built between 1938 and 1946. The reservoir formerly fed Ballagawne Water Treatment Works before the closure of the treatment works in early 2008. With the opening of Douglas Water Treatment Works in 2008, the Cringle Reservoir was decommissioned from being a public water supply reservoir later that year after over 60 years of providing drinking water to the south of the Isle of Man. The drinking water supply for the south is now provided by water from West Baldwin, Clypse and Kerrowdhoo Reservoirs which is treated at Douglas Water Treatment Works.

The reservoir's overflowing water now discharges over a metal rectangular weir and enters a river channel, passing under a highway bridge about 50 metres downstream. It then flows through Silverdale Glen and ultimately joins the Silver Burn River just upstream of Ballasalla, about 5 kilometres downstream of the reservoir. The Silver Burn discharges into the sea at Castletown about 2 kilometres downstream of Ballasalla.

The reservoir is 245 metres at its longest point. The catchment lies to the south of Round Table and South Barrule and consists mainly of open moorland, with extensive forested areas around the margins of the reservoir. Manx slate underlies a relatively thin overburden of boulder clay over most of the catchment.

The reservoir is now used solely for recreational purposes.

Disabled anglers can now fish from a specially designed platform at Cringle Reservoir. The platform is near the disabled users' car park and can be accessed via either a low gradient ramp or steps with hand-rails.

Anglers who are registered as disabled can obtain a key to the disabled users' car park at Cringle Reservoir by contacting our Network and Client Services Team on (01624) 687687.

Reservoir stats

Year completed: 1946
Catchment area: 1.54km²
Capacity: 125,000m³
Surface water area: 18,000m²
Dam height: 21.3m
Depth: 16m
Drinking water supply 
Cringle Reservoir is not currently a drinking water resource reservoir.



Clypse Reservoir from the air

Clypse Reservoir was constructed by Douglas Waterworks Company between 1875 and 1878 to the designs and under the supervision of Daniel Cregeen, a local engineer, and is sited immediately upstream of Kerrowdhoo Reservoir. It is the upper of the two reservoirs in the valley of the Groudle River, above Onchan, and is around 320 metres long.

The dam is an earth fill embankment with a concrete core wall. The upper part of the upstream face of the embankment is protected from wave action by carefully placed stone pitching. The downstream face is predominantly covered by grass but with areas of bracken and brambles.  


Kerrowdhoo Reservoir was constructed between 1891 and 1893 and is the lower of the two reservoirs in the valley of the Groudle River and is about 520 metres long.  

The direct catchment below Clypse is 0.56 square kilometres, making the total combined catchment area for both reservoirs 2.82 square kilometres, rising to over 1,000 feet at Slieau Meayll.The catchment is largely grazing land or open moorland with some areas of forestry.

The dam is an earth embankment with a vertical puddle clay core supported by zoned earth fill shoulders. The upper part of the upstream face is covered in dry rubble pitching about 45 centimetres thick with the top metre steepened. Beaching 45 centimetres thick protects the lower part of the upstream face. The downstream face is protected by 30 centimetres of soil and is grassed.

Following completion of the Kerrowdhoo Reservoir, the normal mode of operation of Clypse Reservoir became to feed water down into the new lower reservoir. The reservoirs supply raw water to Douglas Water Treatment Works.

Reservoir stats




Year completed: 1878 1893
Catchment area: 2.26km² 0.56km² (direct) /  2.82km² (total)
Capacity: 131,000m³ 221,000m³
Depth: 12m 12m
Embankment height: 13.4m 16.3m
Surface water area: 26,000m² 47,000m²
Drinking water supply zone: Both reservoirs supply Douglas, Onchan and the south of the Island.


Ballure Reservoir

In its early years the Ramsey Water Works Company built two concrete walled reservoirs designed to capture and store water flowing down the Ballure stream. The original lower reservoir can still be seen alongside the access road. The original upper reservoir also still exists, but was roofed over and converted into a treated water storage reservoir at the time of construction of the old Water Treatment Works in the 1950s.

By the late 1870s the Ramsey Water Works Company, finding the storage they had available insufficient to maintain supplies to the town during the summer visiting seasons, decided to promote the construction of a new dam across the valley just upstream of their two existing reservoirs, forming a new reservoir holding about 70,000 cubic metres.

Construction of the new dam commenced in the summer of 1881 and was completed in December 1884. The dam is an earth embankment dam of typical design for the period. The base of the valley beneath the dam site is filled with deep deposits of glacial drift material overlying the bed rock.

The direct catchment area is 1.82 square kilometres with additional runoff from a further 4.82 square kilometres collected indirectly from a weir in the Corrany Valley.

The reservoir has not been used as a raw water resource since 2005 following the closure of the old treatment works and is now used solely for recreational purposes. It remains under the ownership of Manx Utilities.

Reservoir stats

Year completed: 1884
Catchment area: 1.82km²
Capacity: 70,000m³
Depth: 11.5m
Embankment height: 17m
Surface water area: 0.0142km²
Drinking water supply zone: Ballure Reservoir is not currently a drinking water resource reservoir.


Sulby Reservoir

Sulby Reservoir is the largest and newest reservoir on the Island. Completed in 1982, the reservoir was formed by the construction of a rock fill embankment dam across the Sulby River just downstream of its confluence with the Druidale stream.

Water from the reservoir is piped to Sulby Water Treatment Works where it is treated and distributed to the population in the north of the Island. Water from Sulby Reservoir can also be pumped to West Baldwin Reservoir, which supplies water to the Douglas area and the south of the Island via Douglas Water Treatment Works.

The reservoir is used to supply water and to generate hydroelectric power from a hydro turbine located about 1.6 kilometres downstream of the dam. In addition to this; in 2013 an energy recovery system was installed at Sulby Water Treatment Works to generate hydroelectric power from incoming raw water. The water then passes through the treatment works and onto our customers.

Reservoir stats

Year completed: 1982
Catchment area: 16.2km²
Capacity: 4,620,000m³
Depth: 52m
Embankment height: 74m
Surface water area: 276,000m²
Drinking water supply zone: St Johns and Peel in the west, Kirk Michael, Ballaugh, Andreas, Bride and Ramsey in the north and Laxey, on the east coast.


West Baldwin Reservoir

The construction of West Baldwin Reservoir began in 1900 by Douglas Corporation Water Works Department and was completed in 1904.

The reservoir is 6 miles north of Douglas, and a railway was required to transport materials to build the reservoir. Construction of the railway line commenced in October 1900 from Sir George's Bridge in Abbeylands up to the site of the dam. Timber bridges had to be made, as the River Glass had to be crossed nine times. The Reservoir was formed by the construction of an earth fill embankment dam across the valley of the River Glass. Half a million tons of earth had to be moved to build the reservoir.  

The dam has a vertical puddle clay core supported by zoned earth fill shoulders. The upper part of the upstream face is faced in dry rubble pitching about 60 centimetres thick. The crest and downstream face are grassed. The maximum depth of water impounded is just over 21 metres.

The reservoir, sometimes known locally as Injebreck Reservoir, is located on the site of 3 properties, the remains of which can be seen when the reservoir is near empty.

The catchment area is moorland lying on Manx slates.

Reservoir stats

Year completed: 1904
Catchment area: 5.66km²
Capacity: 1,290,000m³
Depth: 20m
Embankment height: 22.5m
Surface water area: 168,000m²
Drinking water supply zone: Douglas, Onchan and the south of the Island.


Block Eary Reservoir was constructed during the Second World War and completed in 1945. 

The catchment area is on the steep slopes of Snaefell 4.12 square kilometres and the Block Eary stream flows west into the Sulby River.

The outlet pipework was modified in the 1980s to provide the headrace for a hydropower station situated at the confluence of the Block Eary stream and the Sulby River. The reservoir is now used principally as a source of water for hydroelectric power generation, in conjunction with Sulby Reservoir.

Reservoir stats

Year completed: 1945
Catchment area: 4.12km²
Capacity: 50,000m³
Depth: 11.6m
Embankment height: 16.35m
Surface water area: 7000m²
Drinking water supply zone: Block Eary Reservoir is not currently a drinking water resource reservoir.