O'Shannassy Reservoir

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The O'Shannassy Reservoir is a small reservoir in the southern Australian state of Victoria in the course of O'Shannassy River, above the small town of McMahons Creek, about 80 km east of Melbourne. The reservoir is part of the drinking water supply for Melbourne. The water flows under dynamic pressure to the Silvan Reservoir and then to storage and distribution basin in the Melbourne area. The O'Shannassy reservoir is at 27 hectares the smallest reservoir, which is operated by Melbourne Water. Its memory space is only about 3.1 million m³, but the catchment area is very rich in water, resulting in an average annual flow of about 80 million m³ / year.

The site was chosen because it is high enough to provide the higher eastern suburbs of Melbourne only with the help of the hydrostatic pressure. The diversion weir in O'Shannassy River and the aqueduct to the Surrey Hills Reservoir in Melbourne was completed in 1914. The diversion weir was in 1928 replaced by the reservoir. The construction of the Yarra - Silvan lines in the 1950s led to a lower demand for the aqueduct and 1997 it was decommissioned.