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National Water Account 2018

Sydney: Statement details

  • Well below-average rainfall throughout the year contributed to very low runoff and storage inflows across the region.
  • End of year storage volume dropped to 71% full compared to 94% full last year.

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For further information on the region's water accounting statements scroll down this page or click on the links below:

 

Water assets

  • Water asset volumes in the region at 30 June 2018 were 2,047,235 ML, more than 99% of which is water held in storages; less than 1% is inter-region claims and water held in rivers.

 

Storages

Figure S1 Graph of total storage volume in the region at 30 June 2018 compared with the previous 8 years
Figure S1 Total storage volume in the region at 30 June 2018 compared with the previous 8 years

 

  • Storage volumes decreased from 94% full at 30 June 2017 to 71% (2,042,243 ML) at 30 June 2018, the lowest end of year storage since 2010.
  • Water in Warragamba Reservoir (Lake Burragorang) makes up more than 70% of the region's total surface water storage.

 

Figure S2 Percentage-full volume on 30 June 2018 for each storage
Figure S2 Percentage-full volume on 30 June 2018 for each storage
 

 

  • Storage volumes declined throughout the year due to the very low rainfall.
  • The region's largest storage, Warragamba Reservoir, dropped below 75% full in May–June 2018 for the first time since 2011.
  • Cataract and Cordeaux reservoirs both dropped below 50% full during April–May 2018. This is the first time these storages have been less than 50% full since 2010.
  • More detailed information on the individual storages within the region is available on the Bureau of Meteorology's Water Storage website.

 

Inter-region claims

  • Inter-region claims refer to the volume of allocation remaining on licence entitlements associated with the Fish River Water Supply Scheme at the end of the 2017–18 year.

 

Table S1 Volume of inter-region claims remaining at 30 June 2018
Description Volume (ML)
 Opening balance at 1 July 20172,367
addIncrease of claims: inter-region11,834
lessDelivery: inter-region agreement9,215
lessDecrease of claims: inter-region2,619
 Closing balance at 30 June 20182,367

 

  • The inter-region claim at the end of the reporting year does not change from year to year.
  • A more detailed description of the Fish River Water Supply Scheme is provided in the Region description.

 

Water liabilities

  • Water liabilities in the Sydney region refer to the volume of allocation remaining on licence entitlements at the end of the 2017–18 year.

 

Table S2 Volume of surface water allocation remaining at 30 June 2018
Description Individual users (ML) Urban system (ML)
 Opening balance at 1 July 201700
addAllocation159,3891,040,554
lessAllocated diversion14,651607,174
lessAdjustment and forfeiture144,738433,380
 Closing balance at 30 June 201800

 

  • The water supply licences for the region have a water management year that ends on 30 June. The portion of water allocation that has not been abstracted at the end of the water year is either forfeited or is carried over into the next water year.
  • As the carryover cannot be quantified, the unused portion of the allocation is assumed to be forfeited and the allocation remaining at the end of the year was 0 ML.
  • A more detailed description of water allocations and associated water rights in the Sydney region is given in the Water rights note.

 

Water asset increases

  • Total water asset increases for the region was 2,931,665 ML.
  • The key item contributing to water asset increases for the region was runoff, which made up 44% of the total water asset increases. Runoff was well below average, which reflects the very poor rainfall experienced across the region for the majority of the year.
  • Urban water system increases represent wastewater collected, claims:surface water, and delivery: desalinated water. These volumes generally change little from year to year.

 

Water asset decreases

  • Total water asset decreases for the region was 2,925,863 ML.
  • The key items contributing to water asset decreases for the region were outflow and leakage: groundwater, which combined made up 42% of the total water asset decreases. Outflow was lower than previous years due to well below-average rainfall experienced across the region for the majority of the year (see Climate and water).
  • Urban water system decreases primarily represents supply system delivery: urban users and discharge: sea. The volume of wastewater discharge to sea changes little from year to year; supply system delivery to urban users has generally increased slightly each year over the last five years (see Water stores).

 

Water flows

  • Total water inflows to the region was 2,495,666 ML which differs from the volume of Water asset increases. Total water inflows includes the volume of water delivered under an inter-region claim; total water asset increases includes the actual inter-region claim.
  • Total water outflows from the region was 3,111,689 ML, which differs from the volume of Water asset decreases. Total water outflows includes the flows corresponding to the accrual transactions—allocated diversions. Total water asset decreases includes the forfeiture of inter-region claims (see the Water liabilities section above).
  • A detailed description on all the water inflows and outflows associated with the surface water store and the urban water system is provided in the Water stores note.

 

Unaccounted-for difference

  • The unaccounted-for difference is the volume necessary to reconcile the opening water storage and closing water storage with the total water inflows and total water outflows reported in the water accounting statements.

 

Table S3 Calculation of unaccounted-for difference for the 2017–18 year
Description Volume (ML)
 Closing water storage balance at 30 June 20182,044,868
lessTotal inflows2,495,666
addTotal outflows3,111,689
lessOpening water storage balance at 1 July 20172,691,029
 Unaccounted-for difference(30,138)

 

  • The relatively small unaccounted-for difference value (1% of total water storage) is primarily attributed to uncertainties associated with the runoff estimate (see Methods).