The O'Shannassy Dam is an embankment dam across the O'Shannassy River, located near the locality of , approximately east of Melbourne, Victoria, Australia. Completed in 1928, the resultant eponymous reservoir, the O'Shannassy Reservoir, was formed for the supply of potable water for Greater Metropolitan Melbourne. The dam and reservoir are operated by Melbourne Water.
Dam and reservoir overview Built between 1922 and 1928, the concrete-faced earth-filled dam wall is high and long. When full, the resultant reservoir has a storage capacity of and covers , drawn from a catchment area of . The uncontrolled spillway has a discharge capacity of . In 1987, the spillway was enlarged and the full supply level was lowered.
The reservoir is part of Melbourne's water supply system. Water flows under gravity to Silvan Reservoir, then to storage and distribution reservoirs around Melbourne. It is the smallest of the water storage reservoirs managed by Melbourne Water, and it is on a very productive catchment, with stream flow averaging per annum.
The location was selected as, at , it is at sufficient altitude for gravity supply to the elevated eastern suburbs of Melbourne. In 1914, a diversion weir on the O'Shannassy River and aqueduct to the Surrey Hills Reservoir in Melbourne were completed. The weir was complemented by the construction of the dam and its reservoir in 1928, but the weir was still used to divert river flows into the aqueduct. The construction of the Yarra-Silvan conduits in the 1950s resulted in reduced requirements for the aqueduct which was decommissioned in 1997.
See also
List of reservoirs and dams in Victoria Melbourne Water
References