| O'Shannassy Dam | |
|---|---|
  Location of the O'Shannassy Reservoir inVictoria | |
| Country | Australia |
| Location | McMahons Creek,Victoria |
| Coordinates | 37°40′30″S145°48′20″E / 37.67500°S 145.80556°E /-37.67500; 145.80556 |
| Purpose | Water supply |
| Status | Operational |
| Construction began | 1922[1] |
| Opening date | 1928 |
| Operator(s) | Melbourne Water |
| Dam and spillways | |
| Type of dam | Embankment with an internal reinforced concrete wall |
| Impounds | O'Shannassy River |
| Height | 34 m (112 ft) |
| Length | 226 m (741 ft) |
| Dam volume | 245,000 m3 (8.7 million cu ft) |
| Spillways | 1 |
| Spillway type | Uncontrolled |
| Spillway capacity | 500 cubic metres per second (18,000 cu ft/s) |
| Reservoir | |
| Creates | O'Shannassy Reservoir |
| Total capacity | 3.123 GL (687 million imp gal; 825 million US gal) |
| Catchment area | 11.9 ha (29 acres) |
| Surface area | 27 ha (67 acres) |
| [2] | |
TheO'Shannassy Reservoir is an Australian man-madewater supplydammedreservoir. The 3.123 GL (687 million imp gal; 825 million US gal) water store across theO'Shannassy River is located near the locality ofMcMahons Creek, approximately 80 kilometres (50 mi) east ofMelbourne,Victoria. The dam that creates the impoundment is called theO'Shannassy Dam.[3][4]
The reservoir is part of Melbourne's water supply system. Water flows under gravity toSilvan Reservoir, then to storage and distribution reservoirs around Melbourne. It is the smallest of the water storage reservoirs managed byMelbourne Water, with a capacity of approximately 3.123 GL (687 million imp gal; 825 million US gal), but it is on a very productive catchment, with stream flow averaging 80 GL (18 billion imp gal; 21 billion US gal) per annum.[5][6][7][8]
The location was selected as it is at sufficient altitude for gravity supply to the elevated eastern suburbs of Melbourne. A diversion weir on the O'Shannassy River andaqueduct to theSurrey Hills Reservoir in Melbourne were completed in 1914. 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.[7][8]
