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Sydney: Supporting information

  • Wet conditions in 2020–21 contributed to well above-average annual runoff.
  • End-of-year storage was 97% full compared to 79% full the previous year.
  • 41% of the allocated water was taken in 2020–21, primarily for residential use.

Schematic representation of the Sydney region. In 2020–21, runoff was 84% more than average. Storage volumes at 30 June 2021 were 97% full, higher than the previous year. 40% of the total surface water allocation (1,200 GL) was taken. 24% of the total groundwater allocation (84 GL) was taken.

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

 

Water assets

Cataract Dam, Sydney region (WaterNSW © 2012)

 

  • Water asset volumes in the region at 30 June 2021 were 2,686 GL, more than 99% of which is water held in storages. The remaining amount is water held in rivers.

 

Bar graph of annual storage volume in the Sydney region at 30 June for the years 2010–2021. Accessible storage plus dead storage is plotted against the storage capacity to show percentage full at 30 June each year. Storages at 30 June 2021 were 97% full, higher than the previous four years. Since 2010, the lowest end-of-year storage volume was in 2019 when storages were 52% full. Between 2012 and 2017, end-of-year storage was always above 80% full.
Figure S1 Total storage volume in the region at 30 June 2021 compared with the previous 11 years

 

  • Storage volumes increased from 79% full at 30 June 2020 to 97% full at 30 June 2021.
  • The end-of-year storage volume at 30 June 2021 was the highest since 2016.
  • Water in Lake Burragorang (which is formed by Warragamba Dam) makes up more than 70% of the region's total surface water storage.

 

Map of Sydney region showing the status of each storage at 30 June 2021. The storages are colour coded into ten categories of volume as a proportion of capacity. Warragamba, Prospect, Avon, Blue Mountains, Wingecarribee, and Fitzroy Falls storages were over 80% full. Woronora, Cataract, Cordeaux, and Nepean storages were over 60% full. Tallowa storage was less 20% full. An inset line graph shows the time series of percentage-full storage volume between 1 July 2013–30 June 2021. Sydney storages at 30 June 2021 were 79% full, much higher than last year.
Figure S2 Percentage-full volume on 30 June 2021 for each storage and total storage volume from 2013–2021 (inset)

 

  • High rainfall in August 2020 resulted in a large rise in storage levels. Storage volume increased from 80% full in late-July 2020 to almost full capacity by mid-August 2020.
  • Storage levels exceeded 100% full in late-March 2021 following very heavy rainfall associated with a slow-moving low pressure system that impacted the region in March 2021.
  • Warragamba dam spilled 1,855 GL in addition to environmental flow release because of heavy rainfall in March 2021.
  • More detailed information on the individual storages within the region is available on the Bureau of Meteorology's Water Storage website.

 

Water liabilities

Coastline near Gerringong, Sydney region (Bureau of Meteorology © Merryn Coutts)

 

  • Water liabilities in the Sydney region refer to the volume of allocation remaining on licence entitlements at the end of the 2019–20 year.

 

Table S1 Volume of surface water allocation remaining at 30 June 2021
Description Individual users (ML) Urban system (ML)
  Opening balance at 1 July 2020 0 0
add Allocation 159,390 1,040,554
less Allocated diversion 2,146 510,487
less Adjustment and forfeiture 157,244 530,067
  Closing balance at 30 June 2021 0 0

 

Table S2 Volume of groundwater allocation remaining at 30 June 2021
Description Individual users (ML) Urban system (ML)
  Opening balance at 1 July 2020 0 0
add Allocation 84,534 142
less Allocated diversion 16,918 0
less Adjustment and forfeiture 67,616 142
  Closing balance at 30 June 2021 0 0

 

  • 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 in the Sydney region is given in the Water use section below.

 

Water flows

Hawkesbury River, Sydney region (istock © Leadinglights)

 

Figure S3 Water inflows and outflows for the region's water stores and systems during the 2020–21 year

 

  • Total surface water flows into the region's storages was estimated to be around 10,086 GL. The key item contributing to surface water inflows was runoff, which made up 97% of the total surface water inflows.
  • Runoff was well above average (based on modelled data from 1971–2021) due to the wet conditions throughout most of the year.
  • A key item contributing to surface water outflows from the region's storages was river outflow, which made up 75% of the total surface water outflows. River outflow was more than double the average, largely due to very high rainfall in August 2020 and March 2021.
  • Water taken from surface water and groundwater resources for consumptive use was 562 GL, around 4% of the total outflow (see Water use section below).

 

Water availability

Bar graph of annual surface water availability in the Sydney region for the years 2011–2021. Storage at 1 July plus estimated inflows during the year is plotted against the mean water availability (based on 1971–2021 data). Surface water available during 2020–21 was well above average. Water availability was below average for 5 years between 2016–2021.
Figure S4 Annual surface water available in the Sydney region, 2011–12 to 2020–21

 

  • Physical surface water availability is calculated as the sum of storage at the start of the year (see Water assets) and estimated inflows into storages and rivers during the year (see Figure S3).
  • Surface water availability in the Sydney region in 2020–21 was well above average and the region's highest in more than ten years.
  • As physical water availability is much higher than the region's water needs, water allocations vary little between years.

 

Water use

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

 

Doughnut graphs of water supplied to different users in 2019–20. Surface water taken in the Sydney region was 545 GL, mostly for the urban system. Groundwater taken was 17 GL, all for individual users.
Figure S5 Water taken for consumptive use in the Sydney region in 2020–21

 

  • Total surface water diverted in the region was 544,890 ML.
  • 94% of the total diversion was for urban supply, almost entirely to the Sydney Water Corporation.
  • 6% of the total diversion was for individual users under a statutory right; less than 1% was for individual users under an allocation.
  • Total groundwater extracted in the region was 16,918 ML, all of which was for individual users.

 

Bar graph of annual surface water allocation and diversion for different users in the Sydney region from 2011–12 to 2019–20. Most of the surface water allocations are associated with the urban system. Allocations for the urban system have remained unchanged since 2011–12. In 2020–21, 49% of the allocation for the urban system was taken, lower than the previous year. 1% of the allocation for individual users was taken. Non-allocated surface water is also taken for individual users under a statutory right.
Figure S6 Surface water allocations and diversions in the Sydney region for the years ending 30 June, from 2012–2021

 

  • In 2020–21, total surface water allocation was 1,200 GL, mostly for urban system supply. 43% of the allocated surface water was taken.
  • Diversions to the urban system were higher than the previous year. The higher surface water supply was influenced by the better water availability to meet urban demand.
  • Total groundwater allocation was 85 GL, mostly for irrigation or industrial purposes. 20% of the allocated groundwater was used.

 

Urban system supply

Stacked bar graph showing the annual water sourced for Sydney region's urban supply system during the period from 2010–11 to 2020–21. Each bar in the stack progressively represents surface water, inter-region inflow, and desalinated water. Between 2010–11 and 2017–18 there was a general increasing trend in total water sourced for the urban system. Since 2017–18, there have been two consecutive decreases in total annual water sourced. Surface water is the predominant water source for the urban system. Desalinated water has been a source of water for the urban system for the last 2 years, as well as a 2-year period between 2010–2012. Key aspects of the graph are described in the text below the figure.
Figure S7 Water sources used in the Sydney region's urban supply system during the 2020–21 year compared with the previous ten years

 

  • Total inflow to the water supply system was 530,096 ML, slightly lower than last year.
  • Surface water diversion from the region's storages made up 96% of the urban water supply.
  • Desalinated water made up 4% of urban supply, much lower than the last year.

 

Water restrictions

 

  •  In December 2020, The NSW Government has announced that Water Wise Guidelines have replaced Level 1 water restrictions and apply to everyone in Sydney, the Blue Mountains and the Illawarra. This includes all residents and businesses.
  • Reference: Water Restrictions.

 

Cultural and environmental water

Wingecarribee Reservoir, Sydney region (istock © Phillip Minnis)

 

Cultural benefit

  • Cultural water values within the region are closely aligned with environmental water outcomes.
  • More information on cultural water requirements are provided in the Cultural water management section in the 'Region description'.

 

Environmental benefit

  • Provisions to protect the environmental values of water systems are defined in the region's water sharing plans.
  • Each year, environmental flow releases are made at various river locations across the region.

 

Map of environmental releases at 11 river locations. 610,715 ML and 12,147 ML of water were released to the environment from downstream of Tallowa and Fitzroy Falls storages, respectively in the region's south. 42,914 ML, 22,302 ML, 16,796 ML, and 12,721 ML was released from Pheasants Nest, Broughtons, Cataract, and Nepean respectively, near the region's central coast. 28,231 ML of water was released from the remaining 5 river locations.
Figure S8 Surface water environmental flow releases in 2020–21

 

  • In 2020–21, environmental flow releases were made at 11 river locations throughout the region. The total volume released was 746 GL.
  • Improved surface water availability across the region meant the total volume released was much higher compared to the last four years.
  • The largest environmental release, representing about 82% of the total, occurred in the Shoalhaven River below Tallowa Dam (Lake Yarrunga).