Looking for info about dams? Get to know Melbourne's water storage reservoirs, which help secure our water supply now and into the future.
What is a reservoir?
A reservoir is a large natural or artificial storage of water usually formed by constructing a dam across a river.
Our 10 major reservoirs store water collected from the catchments, and other sources, for example, the Victorian Desalination Plant. Together, they have a storage capacity of 1,810 billion litres, and vary in size from the smaller O’Shannassy (3 billion litres) to the massive Thomson (1,068 billion litres).
Types of reservoirs
There are two types of reservoirs
on-stream reservoirs, where rainfall across Melbourne's water catchments drive the amount of water that flows into these reservoirs.
off-stream reservoirs, where water is transferred from on-stream reservoirs or other sources: for example, Sugarloaf Reservoir, which can receive water from the North-South Pipeline.
The reservoirs are connected so we can move water around the water supply system, based on factors such as rainfall and demand.
Did you know...
Thomson Reservoir is the largest but most of Melbourne’s water is supplied via Silvan Reservoir? Read why
Meet our on-stream reservoirs, their capacity and how they are fed. Click to discover what makes them unique:
|Reservoir||Source of water||
Capacity (billion litres)
|Thomson||Thomson catchment, located in Thomson State Forest and a small part of Baw Baw National Park||1,068|
|Upper Yarra||Upper Yarra catchment, in the Yarra Ranges National Park||200|
|Tarago||Bunyip State Forest||37|
|Yan Yean||Combination of Toorourrong catchment, Silvan Reservoir and Winneke treatment plant||30|
|Maroondah||Watts River catchment and Graceburn Creek||22|
|O'Shannassy||O’Shannassy River and Smith Creek||3|
Meet our off-stream reservoirs, their capacity, and the areas they supply water to. Click through for more details.
|Reservoir||Areas supplied||Capacity (billion litres)|
|Cardinia||Most parts of Melbourne, especially the south and south-eastern suburbs||287|
|Sugarloaf||North, west and central Melbourne||96|
|Silvan||Most parts of Melbourne||40|
|Greenvale||North-west and west Melbourne||27|
How we calculate water storage levels
Melbourne’s water storage levels are expressed as a percentage of the combined capacity of all storage reservoirs.
This is more accurate than looking at individual reservoirs because of their vast differences in storage capacity. For example, the amount of water needed to completely fill O’Shannassy Reservoir would only fill 0.3% of Thomson Reservoir.
Find out more about water storage levels at our most visited page, Water storage and use.