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National Water Account 2019

Sydney: Water stores

  • Dry conditions contributed to very low runoff across the region and a decrease in storage volumes.
  • 92% of the region's water supply was for urban use, most of which came from surface water storages.
  • Water supply for urban use was 571 GL, about 6% less than 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

Warragamba Reservoir, Sydney region (WaterNSW © 2014)

 

Table S4 Water balance for the surface water store
Description Volume (ML)
  Opening surface water store 2,047,235
add Inflows 1,549,891
less Outflows 2,483,429
add Balancing item 338,333
  Closing surface water store 1,452,030

 

  • The volume of surface water in the region decreased from 2,047 GL at 1 July 2018 to 1,452 GL at 30 June 2019.
  • The balancing item is almost one quarter of the closing surface water store and is primarily attributed to uncertainties associated with the runoff and 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 609 GL.
  • 93% of the total diversion was for urban supply, almost entirely to the Sydney Water Corporation.
  • 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.

 

Groundwater store

Wingecarribee Reservoir, Sydney region (istock © Phillip Minnis)

 

Table S5 Water balance for the groundwater store
Description Volume (ML)
  Opening groundwater store –
add Inflows 751,985
less Outflows 3,409
add Balancing item (748,576)
  Closing groundwater store –

 

  • The volume of groundwater in the region is assumed to remain unchanged throughout the year.
  • The large groundwater balancing item is primarily due to the fact that key groundwater fluxes, including discharge to the landscape and to the rivers, cannot be quantified.

 

Groundwater flows

Figure S4 Water inflows and outflows for the groundwater store during the 2018–19 year

 

  • Groundwater movement across the region boundary, as well as surface water–groundwater interactions, are considered to occur within the region; however, most of these flows could not be quantified due to a lack of available data.
  • Total groundwater extracted in the region was 3,409 ML.
  • All of the groundwater extractions were for individual users.
  • For a more detailed description of the water usage in the region, and the associated entitlements, see the Groundwater rights note.

 

Urban water system

Wollongong Water Recycling Plant, Sydney region (Sydney Water Corporation © 2010)

 

Table S6 Water balance for the urban water system
Description Volume (ML)
  Opening urban water system –
add Inflows 1,089,460
less Outflows 1,087,600
add Balancing item (1,860)
  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). The balancing item for the urban system is generally relatively small as the system is controlled and contained.

 

Urban water system flows

Figure S5 Water inflows and outflows for the urban water system during the 2018–19 year

 

Water supply inflows

Graph of water sources used in the Sydney region's urban supply system during the 2018–19 year compared with the previous eight years

Figure S6 Water sources used in the Sydney region's urban supply system during the 2018–19 year compared with the previous eight years

 

  • Total inflow to the water supply system was 571,076 ML, approximately 6% less than last year.
  • Last year the region experienced even drier conditions than in 2018–19, resulting in a relatively high water demand from customers. Urban supply this year was similar to the volume diverted the previous year in 2016–17.
  • Surface water diversion from the region's storages made up 99% of the urban water supply.
  • Desalinated water, which made up 1% of urban supply, was used for the first time since 2011–12. The desalination plant commenced operation in January 2019 when WaterNSW's total operating storage capacity dropped below 60%.

 

Wastewater and recycled water inflows

  • Wastewater collected was 518,384 ML during the 2018–19 year.

 

Water supply outflows

Graph of outflows from the water supply system

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 water supply system was related to losses.

 

Wastewater and recycled water outflows

Graph of outflows from the wastewater and recycled water systems
 Figure S8 Outflows from the wastewater and recycled water systems

 

  • 3% of the treated wastewater was recycled water delivery to urban users.
  • Most of the remaining treated wastewater was discharge to sea and, to a much lesser extent, discharge to surface water.