Water Distribution
An extensive supply system distributes water from Melbourne’s major water storage reservoirs to the city's 3 retail water companies and their customers.
Melbourne Water operates and maintains:
- 1,018 kilometres of water distribution mains;
- 361.5 kilometres of aqueducts, siphons and tunnels;
- 55 service reservoirs at 36 local sites;
- 63 water treatment plants; and
- 23 pump stations.
Water collection and distribution
Collection
The majority of Melbourne’s water catchments are in forested areas high up in the Yarra ranges. These native forests catch, hold and filter rainwater as it flows across land into streams and then reservoirs.
Water storage reservoirs
Water from the catchments is normally stored in one of Melbourne’s ten storage reservoirs.
Water is stored for long periods of time to ensure purification. Over several months, sediment in the water settles to the bottom of the reservoir and sunlight helps to disinfect the water.
These reservoirs have a combined capacity of 1,810,500 million litres of water.
Melbourne’s largest reservoir is the Thomson. It contributes about 60 per cent of Melbourne’s total reservoir storage capacity.
Reservoir Capacity (million litres - ML)
| Thomson Reservoir | 1,068,000 |
 View enlarged version |
| Cardinia Reservoir | 287,000 | |
| Upper Yarra Reservoir | 200,000 | |
| Sugarloaf Reservoir | 96,000 | |
| Silvan Reservoir | 40,000 | |
| Tarago Reservoir | 37,500 | |
| Yan Yean Reservoir | 30,000 | |
| Greenvale Reservoir | 27,000 | |
| Maroondah Reservoir | 22,000 | |
| O'Shannassy Reservoir | 3,000 | |
| Total | 1,810,500 |
Distribution
From the major reservoir storages, water flows by gravity (or is pumped) through large pipes (distribution mains) to service reservoirs. There are about 55 service reservoirs throughout the metropolitan area, which provide short-term storage (1-2 days) to ensure a constant water supply during peak demand periods.
From the service reservoirs, water flows by gravity through a smaller pipe system to the metropolitan retail water businesses, which then supply the water to homes, schools and businesses.
Thousands of kilometres of pipes carry the water in a web-like network. These pipes are largely underground.
Water pressure is carefully managed to ensure that it is adequate but not so high that it causes damage to household plumbing appliances.