Kerrowdhoo Reservoir

Kerrowdhoo Reservoir is the lower of the two reservoirs in the valley of the Groudle River, its catchment area is therefore the same as that of Clypse Reservoir and covers 562 acres.

The reservoir was constructed during the period 1891 to 1893 to the designs of William Fox of London but the Water Committee of Douglas Town Commissioners required the design and drawings to be approved by the eminent dam engineer G H Hill of Manchester. The construction work was carried out by contractors Messrs R H & H Hodgson.

The reservoir was formed by an earth embankment which has an upstream slope of 1 in 2 and a downstream slope of 1 in 3, the upper part of the upstream face is protected from wave action by carefully placed stone pitching. The downstream face is covered with grass. The embankment is made watertight by a central puddle clay core which is taken well down into the underlying boulder clay by means of a cut-off trench, this too is filled with puddle clay. The draw-off works comprise a single 24 inch diameter pipe which combines both supply and scour functions. The flow of water into the draw-off pipe is controlled by three 15 inch diameter draw-off valves located at different levels in the wet well draw-off tower. The valves are operated by spindles from the top of the segmental cast iron draw-off tower which is reached by means of a steel lattice footbridge. The original footbridge was replaced in the 1950's and again in early 2002.

The reservoir contains water to a depth of 40 feet and stores 50 million gallons of water up to the level of the overflow cill at 392 feet and, at this level the water surface extends to 11.6 acres. The estimated reliable yield from both Clypse and Kerrowdhoo Reservoirs is 500,000 gallons per day.

The original overflow from the reservoir was formed by a concrete cill and discharge channel which cascades the water down the mitre of the embankment into the river below. The original overflow is to be enlarged during 2002 to comply with current flood standards. The flow into the reservoir can be by -passed around the western flank of the reservoir by means of a concrete lined bywash channel.

From the dam down to the old Ballacain Reservoir, there are two mains, the original 12-inch diameter cast iron Clypse main laid circa. 1878 and a 15 inch diameter asbestos cement laid in 1964 which continues down into Onchan village, where it joins into a 15 inch diameter cast iron main laid in 1933 in association with the original development of the Glencrutchery Water Treatment Works. This 15-inch diameter cast iron main then continues along the main road to Glencrutchery. At the Glencrutchery Water Treatment Works, raw water from Kerrowdhoo and West Baldwin Reservoirs is blended prior to pressure treatment in a single process stream.

Because of the difference in elevation between the two sources, water drawn from the Kerrowdhoo needs to be pumped into the works inlet, using booster pumps installed within the Water Treatment Works.