Contemplate for a moment: How does a city like Melbourne quench its thirst? The answer lies partly before you at the O’Shannassy Reservoir.
Welcome to the O’Shannassy Reservoir. It is more than just a body of water. It is a vital artery in Melbourne’s water supply system. This reservoir, nestled near McMahons Creek, is about 80 kilometers east of Melbourne.
The O’Shannassy Reservoir may be the smallest of Melbourne’s water storage facilities. It has a capacity of 3.123 GL. But do not let its size fool you. Its location boasts a productive catchment area. Stream flow averages about 80 GL per year. That is quite impressive for its size.
Back in 1914, engineers built a diversion weir on the O’Shannassy River. They constructed an aqueduct to the Surrey Hills Reservoir. Then, in 1928, the O’Shannassy Dam and its reservoir came to life. Even with the dam, they still used the weir to divert river flows into the aqueduct.
The location was chosen wisely. Its altitude allows gravity to supply water to Melbourne’s eastern suburbs. This clever design reduced the need for pumping. It also saved energy. In the 1950s, the Yarra-Silvan conduits further improved the system. As a result, the aqueduct became less critical. It was finally decommissioned in 1997.
The O’Shannassy Dam itself is an impressive structure. It is an embankment dam with an internal reinforced concrete wall. The dam stands 34 meters high and stretches 226 meters long. Its volume is about 245,000 cubic meters. The reservoir’s surface area covers 27 hectares. The O’Shannassy Reservoir catchment area spans 11,900 hectares. That is a substantial area collecting rainfall.
When the O’Shannassy Reservoir overflows, the excess water flows into the Yarra River. From there, some of it can be pumped back into Sugarloaf Reservoir. This ensures that no drop goes to waste.
Melbourne Water manages the O’Shannassy Reservoir. They ensure the water meets the city’s needs. They also protect the surrounding catchment areas.
Annual rainfall at O’Shannassy varies significantly. The wettest year on record saw a staggering 2166.9 mm of rain. The driest year recorded a mere 829.4 mm. The average annual rainfall is around 1373.3 mm. August typically sees the most rainfall. February usually has the least.
While the protected water supply catchment is off-limits, the O’Shannassy Aqueduct Trail welcomes pedestrians. This allows visitors to appreciate the area’s natural beauty. They can also learn about its vital role in Melbourne’s water supply.
The O’Shannassy Reservoir sends its water to Silvan Reservoir. From there, it is distributed to most parts of Melbourne. This gravity-fed system highlights the ingenuity of early engineers.
So, as you stand here, remember that the O’Shannassy Reservoir is more than just a pretty view. It is a crucial piece of Melbourne’s infrastructure. It is a testament to human ingenuity and the importance of water management. A true feat of engineering ensuring that taps keep flowing in Melbourne.