Sydney: Water stores
- Well below-average rainfall throughout the year contributed to very low runoff across the region and a decrease in storage volumes.
- Water use was higher than last year reflecting the very dry conditions.
For a water balance of each of the region's water stores for the 2017–18 year scroll down this page or click on the links below:
Surface water store
| Description | Volume (ML) | |
| Opening surface water store | 2,691,029 | |
| add | Inflows | 1,426,950 |
| less | Outflows | 2,060,036 |
| add | Balancing item | (13,075) |
| Closing surface water store | 2,044,868 | |
- The volume of surface water in the region decreased from 2,691,029 ML at 1 July 2017 to 2,044,868 ML at 30 June 2018.
- The balancing item is negligible relative to the closing surface water store. The balancing item is primarily attributed to uncertainties associated with the runoff and outflow estimates (see Methods).
Surface water flows
Figure S4 Water inflows and outflows for the surface water store during the 2017–18 year
- The largest natural water flows were runoff and outflow. Both were well below average compared to previous years, reflecting the relatively poor rainfall experienced across the region for the majority of the year (see Climate and water).
Figure S5 Surface water diversions to the urban system by WaterNSW during the 2017–18 year
- Total surface water diverted in the region was 654,082 ML, 93% of which was for urban supply by the bulk supplier WaterNSW.
- 2% of the total diversion was for individual users under an allocation; 5% was for individual users under statutory rights.
- For a more detailed description of the water usage in the region, and the associated entitlements, see the Surface water rights note.
Urban water system
| Description | Volume (ML) | |
| Opening urban water system | – | |
| add | Inflows | 1,068,716 |
| less | Outflows | 1,051,653 |
| add | Balancing item | (17,063) |
| Closing urban water system | – | |
- The volume of water in the region's urban system comprises water in the pipe network. As no major pipe network changes were made, this volume is assumed to remain unchanged throughout the 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 S6 Water inflows and outflows for the urban water system during the 2017–18 year
Water supply inflows
Figure S7 Water sources used in the Sydney region's urban supply system during the 2017–18 year compared with the previous 7 years
- Total inflow to the water supply system was 607,174 ML, approximately 8% higher than last year. This increase was primaily due to an increased demand from customers in response to the drier conditions across the region.
- Surface water diversion from the region's storages made up 100% of the urban water supply.
- No desalinated water has been required to meet urban demand for the past six years.
Wastewater and recycled water inflows
- Wastewater collected was 461,542 ML during the 2017–18 year.
Water supply outflows
Figure S8 Outflows from the water supply system
- The majority of water supply outflows was supply system delivery: urban users.
- 10% of the total outflow from the urban water supply system was related to losses, similar to the previous year.
Wastewater and recycled water outflows
Figure S9 Outflows from the wastewater and recycled water systems
- 3% of the treated wastewater was recycled water delivery: urban users, similar to the previous year.
- Most of the remaining treated wastewater was discharge: sea and, to a much lesser extent, discharge: surface water.