Bureau Home » Water Information » National Water Account » 2016 Account » Sydney » Supporting information » Statement details

National Water Account 2016

Sydney: Statement details

High rainfall and runoff associated with several east coast low events that occurred during the 2015–16 year contributed to an increase in water storage from 93% full at the start of the year to 98% full at 30 June 2016. Aside from these events, streamflow and storage inflows across the region were relatively low.

 


 

 

Water assets

Surface water assets

Surface water asset volumes in the Sydney region at 30 June 2016 were 2,823,922 ML, which comprised water held in storages (2,813,671 ML), unregulated rivers (7,884 ML), and inter–region claims (2,367 ML). The location of each storage within the region and the volume of water in each storage as a percentage of total storage capacity at the end of the year is shown in Figure S1.

The volume of water in regulated rivers, and lakes and wetlands could not be quantified due to a lack of available data; however, the volume of water held in rivers and lakes is considered to be relatively small compared to the volume held in storages.

 

Figure S1 Percentage-full volume on 30 June 2016 for each storage
Figure S1 Percentage-full volume on 30 June 2016 for each storage

 

The overall storage volume within the Sydney region increased during the 2015–16 year from 93% to 98% full at 30 June 2016 (Figure S2). This was largely due to heavy rainfall associated with three east coast low events that occurred during the year, particularly the event on 5–6 June 2016. This caused very high streamflows and storage inflows for the remainder of the year (see Climate and water). Prior to this early-June event, the storage volume was less than that at the start of the 2015–16 year. 

Information on the individual storages within the region is given on the Bureau of Meteorology's Water Storage website.

 

Figure S2 Total storage volume in the region at 30 June 2016 compared with the previous 6 years
Figure S2 Total storage volume in the region at 30 June 2016 compared with the previous 6 years
 

 

Surface water claims in the Sydney region (2,367 ML) were the carryover associated with the Fish River Water Supply Scheme for WaterNSW and Energy Australia at the end of the 201516 year. Each agency has an annual maximum allocation entitlement from the Fish River Water Supply Scheme to supply water to their storages. The maximum carryover volume is 20% of the total allocation entitlement (WaterNSW: 3,650 ML and Energy Australia: 8,184 ML).

 

Table S1 Volume of surface water inter-region claims remaining at the end of the 2015–16 year
 Volume
ML
Opening balance at 1 July 20152,367
Increase of claims11,834
Delivery: inter-region agreement(4,448)
Decrease of claims(7,386)
Closing balance at 30 June 20162,367

 

Groundwater assets

The Sydney region's groundwater assets are not presented in the statements as volumes related to the groundwater store could not be quantified in a way that was complete, neutral, and free from material error. In addition, the volume of water held in aquifers is considered to be relatively small compared to the volume held in the surface water store.

 

Water liabilities

Water liabilities in the Sydney region refer to the volume of allocation remaining on licence entitlements at the end of the 2015–16 year for individual users.

The water supply licences for the region have a water management year that ends on 30 June. The portion of surface 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. According to the Water Sharing Plan for the Greater Metropolitan Region Unregulated River Water Sources (NSW Office of Water 2011a), carryover of any unused allocation at the end of the year is allowed. The maximum volume of carryover allowed is determined by the rules in the water sharing plan and the volume of water diverted under the licence. Due to limited data availability, however, the carryover volume could not be quantified. For the purposes of the 2016 Account, the unused portion of the allocation was forfeited and the remaining allocation was zero.

A more detailed description of water allocations and associated water rights in the Sydney region is given in the Surface water rights note.

 

Table S2 Volume of surface water allocation remaining for individual users at 30 June 2016
 Volume
ML
Opening balance at 1 July 20150
Allocation 159,390
Allocated diversion(20,501)
Adjustment and forfeiture (138,889)
Closing balance at 30 June 20160

 

Water asset increases

Total water asset increases for the region (5,609,108 ML) comprised:

  • surface water increases—5,061,325 ML
  • urban water system increases—547,783 ML.

The key water asset increase for the region was runoff, which made up more than 87% of the total water asset increases. This flow is very climate-dependent and was less than the previous year, which reflects the relatively below-average rainfall experienced across the region for the majority of the year (see Climate and water).

Urban water system increases represent wastewater collected, which generally changes little from year-to-year.

 

Water asset decreases

Total water asset decreases for the region (5,242,968 ML) comprised:

  • surface water decreases—4,226,406 ML
  • urban water system decreases—1,016,562 ML.

The key surface water asset decrease for the region was outflow, which made up more than 95% of the total surface water asset decreases. This flow is very climate-dependent and was less than the previous year, which primarily reflects the relatively below-average rainfall experienced across the region for the majority of the year (see Climate and water).

Urban water system decreases primarily represent 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 Urban water store note).

 

Water flows

Total water inflows to the region (5,601,722 ML) were less than the volume of Water asset increases (5,609,108 ML) because the volume of water asset increases includes an inter-region claim on surface water (11,834 ML); whereas, the volume of water inflows includes the delivered portion of that inter-region claim (4,448 ML).

Total water outflows from the region (5,256,083 ML) were higher than the volume of Water asset decreases (5,242,968 ML) because the volume of water outflows also includes the flows corresponding to the accrual transactions; that is, the allocated water diversions (see the Water liabilities section above).

A detailed description on all the water inflows and outflows associated with the surface water store and urban water system are provided in the Water stores note.

 

Unaccounted-for difference

The volume recognised in the water accounting statements (–189,050 ML) represents the total unaccounted-for difference for the Sydney region for the 2015–16 year.

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. It is calculated according to Table S3.

 

Table S3 Calculation of unaccounted-for difference for the 2015–16 year
 Volume
ML
Opening water storage balance at 1 July 20152,664,966
Total water inflows5,601,722
Total water outflows(5,256,083)
Closing water storage balance at 30 June 2016(2,821,555)
Unaccounted-for difference(189,050)

 

The unaccounted–for difference can also be calculated by adding the volumes necessary to reconcile (balance) the opening and closing storage with the water inflows and outflows of each of the separate water stores of the region, as shown in Table S4.

 

Table S4 Balancing volumes of the water stores of the Sydney region for the 2015–16 year
 Volume
ML
Surface water store(173,834)
Urban water system(15,216)
Unaccounted-for difference(189,050)

 

The unaccounted–for difference volume is primarily explained by the balancing item of the surface water store. The surface water balancing item is largely attributed to uncertainty associated with runoff to surface water and river outflow, and the volume of river and floodplain losses not being able to be quantified (see Surface water note).