Melbourne: Water stores
- Dry conditions contributed to very low runoff across the region and a decrease in storage volumes.
- 91% of the region's water supply was for urban use, most of which came from surface water storages.
- Water supply for urban use was 466 GL, similar to last year.
For a water balance of each of the region's water stores for the 2018–19 year scroll down this page or click on the links below:
Surface water store
| Description | Volume (ML) | |
| Opening surface water store | 1,181,590 | |
| add | Inflows | 783,196 |
| less | Outflows | 1,226,379 |
| add | Balancing item | 291,975 |
| Closing surface water store | 1,030,382 | |
- The volume of surface water in the region decreased from 1,182 GL at 1 July 2018 to 1,031 GL at 30 June 2019.
- The balancing item is almost 30% of the closing surface water store and is primarily attributed to uncertainties associated with the runoff and the river outflow estimates (see Methods).
Surface water flows
Figure S3 Water inflows and outflows for the surface water store during the 2018–19 year
- The largest natural water flows were runoff and outflow. Both were well below average reflecting the dry conditions experienced across the region (see Climate and water).
- Total surface water diverted in the region was 469,337 ML.
- 95% of the total surface water diverted was for urban system supply, mostly by the Melbourne Water Corporation.
- 4% of the total diversion was for individual users (comprising allocated and non-allocated diversions) while 1% was for inter-region supply.
- For a more detailed description of the water usage in the region, and the associated entitlements, see the Surface water rights note.
Groundwater store
| Description | Volume (ML) | |
| Opening groundwater store | 38,619 | |
| add | Inflows | 290,791 |
| less | Outflows | 151,343 |
| add | Balancing item | (139,448) |
| Closing groundwater store | 38,619 | |
- The volume of groundwater in the region is equivalent to the permissible consumptive volume, which is the legal extractable limit and, therefore, remains unchanged from year to year.
- The relatively high balancing item is due to the fact that groundwater fluxes such as discharge to the landscape and to the rivers cannot be quantified, as well as the assumption of constant volume in the groundwater store.
Groundwater flows
Figure S4 Water inflows and outflows for the groundwater store during the 2018–19 year
- The largest groundwater inflows were recharge: landscape and recharge: surface water, which combined account for almost 80% of the total groundwater inflows.
- Recharge was less than average reflecting the relatively poor rainfall and streamflow conditions across the region throughout most of the year (see Climate and water).
- Total groundwater extracted in the region was 21,032 ML.
- More than 99% of the total groundwater extracted was for individual users; less than 1% was for the urban water system.
- For a more detailed description of the water usage in the region, and the associated entitlements, see the Groundwater rights note
Urban water system
| Description | Volume (ML) | |
| Opening urban water system | 28,419 | |
| add | Inflows | 825,973 |
| less | Outflows | 815,898 |
| add | Balancing item | (9,685) |
| Closing urban water system | 28,809 | |
- The volume of water in the Melbourne region's urban water system includes water held in wastewater treatment plant lagoons and holding basins. This volume changes little from year to year.
- The balancing item is attributed to metering inaccuracies, unaccounted losses, and inaccuracies in the estimation of certain volumes (see Methods).
Urban water system flows
Figure S5 Water inflows and outflows for the urban water system during the 2018–19 year
Water supply inflows
Figure S6 Water sources used in the Melbourne region's urban supply system during the 2018–19 year compared with the previous eight years
- Total inflows to the water supply system was 466,342 ML, similar to last year.
- 95% of the total urban supply was from surface water storages. Desalinated water made up almost 5% of urban supply while less than 1% was from groundwater extractions.
- The increase in production of desalinated water meant there was less reliance on surface water for urban supply compared to last year.
Wastewater and recycled water inflows
- Wastewater collected was 359,631 ML during the 2018–19 year.
Water supply outflows
Figure S7 Outflows from the water supply system
- The majority of water supply outflow was supply system delivery to urban users.
- 10% of the total outflow from the urban supply system was related to losses. Losses have decreased during the past three years compared to previous years mainly due to closer monitoring of night flows, as well as reduced response and repair times following pipe bursts.
Wastewater and recycled water system outflows
Figure S8 Outflows from the wastewater and recycled water systems
- 15% of the treated wastewater was recycled, most of which was recycled water delivery to urban user.
- Most of the remaining treated wastewater was discharge to sea.
- 5% of the total outflow was related to losses.