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Melbourne: Supporting information

  • Above-average rainfall contributed to high runoff and storage inflows across the region.
  • Total storage at 30 June 2021 was 75% full, the highest end of year storage since 2014.
  • 36% of the allocated water was taken in 2020–21, primarily for residential use.

Schematic representation of the Melbourne region. In 2020–21, runoff was 8% more than average. Storage volumes at 30 June 2021 were 75% full, higher than the previous year. 38% of the total surface water allocation (881 GL) was taken. 25% of the total groundwater allocation (69 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

Werribee River lower reaches, Melbourne region (Alison Pouliot © 2010)

 

  • Total water asset volumes in the region at 30 June 2021 were 2,157 GL, 69% of which is water held in storages.
  • Around 27% of the water assets are claims on water for the urban system. About 4% of the asset volume is water held in rivers, aquifers, and the urban system's wastewater storages.

 

Bar graph of annual storage volume in the Melbourne 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 75% full. Since 2010, the highest end-of-year storage volume was in 2014 and 2021 when storages were 75% full, the lowest was in 2010 when storages were 36% full.
Figure S1 Total storage volume in the region at 30 June 2021 compared with the previous 11 years

 

  • Storage volumes increased from 66% full at 30 June 2020 to 75% full at 30 June 2021.
  • The end-of-year storage volume at 30 June 2021 was the highest since 2014.

 

Map of Melbourne 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. Tarago, Silvan, Sugarloaf, Yan Yean, Maroondah, Greenvale, and Pykes Creek storages were over 80% full. Cardinia and Melton storages were over 60% full. O'Shannassy, Merrimu, and Rosslynne storages were less than 50% full. An inset line graph shows the time series of percentage-full storage volume between 1 July 2013–30 June 2021. Melbourne storages at 30 June 2021 were 66% full, higher than last year.
Figure S2 Percentage-full volume on 30 June 2021 for each storage and total daily storage volume from 2013–2021 (inset)

 

  • Storage volumes peaked in late-November 2020 following rainfall during the winter–spring months.
  • High rainfall in June 2021 resulted in a second rise in storage levels across the region.
  • More detailed information on the individual storages within the region is available on the Bureau of Meteorology's Water Storage website.

 

Water liabilities

Werribee river shoreline (Bureau of Meteorology © Brett Anderson)

 

  • Water liabilities in the Melbourne region refer to the volume of allocation remaining on licence entitlements at the end of the 2020–21 year.

 

Table S1 Volume of surface water allocation remaining at 30 June 2021
DescriptionIndividual users (ML)Urban system (ML)Transfer: inter-region
 Opening balance at 1 July 202011,229535,8020
add Allocation22,726852,6465,225
less Allocated diversion8,664315,1253,647
less Adjustment and forfeiture13,840487,8991,578
 Closing balance at 30 June 202111,451585,4240

 

Table S2 Volume of groundwater allocation remaining at 30 June 2021
DescriptionIndividual users (ML)Urban system (ML)
 Opening balance at 1 July 202000
add Allocation67,9861,499
less Allocated extraction17,55976
less Adjustment and forfeiture50,4271,423
 Closing balance at 30 June 202100

 

  • As there are no carryover provisions for groundwater supply licences in the region, the portion of water allocation that has not been abstracted at the end of a water year is forfeited and the allocation remaining at the end of the year was 0 ML.
  • A more detailed description of water allocations in the Melbourne region is given in the Water use section below.

 

Water flows

Werribee river, Melbourne region (Bureau of Meteorology © Brett Anderson)

 

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 1,884GL. The key item contributing to surface water inflows was runoff, which made up 75% of the total surface water inflows.
  • For the second consecutive year, runoff was above average (based on modelled data from 1971–2021) due to the above-average rainfall across the region.
  • A key item contributing to surface water outflows from the region's storages was river outflow, which made up 52% of the total surface water outflows. River outflow was above average due to the wet conditions and high runoff across the region.
  • Water taken from surface water and groundwater resources for consumptive use was 356 GL, around 12% of the total outflow (see the Water use section below).

 

Water availability

Bar graph of annual surface water availability in the Melbourne 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 above average for the second consecutive year. Water availability was well below average during 2018–19.
Figure S4 Annual surface water available in the Melbourne 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 Melbourne region in 2020–21 was above average for the second consecutive year.
  • Water accessible for use is influenced by the physical water availability. Typically, water accessible for take is higher when water availability is high. This is discussed in more detail in the Water use section below.

 

Water use

City of Melbourne, aerial view (istock © BluesandViews)

 

Doughnut graphs of water supplied to different users in 2020–21. Surface water taken in the Melbourne region was 327 GL, mostly for the urban system. Groundwater taken was 18 GL, mostly for individual users.
Figure S5 Water taken for consumptive use in the Melbourne region in 2020–21

 

  • Total surface water diverted in the region was 338,275 ML.
  • 94% of the total surface water diverted was for urban system supply, mostly by the Melbourne Water Corporation; 5% was for individual users (comprising allocated and non-allocated diversions) while 1% was for inter-region supply.
  • Total groundwater extracted in the region was 17,635 ML.
  • More than 99% of the total groundwater extracted was for individual users; less than 1% was for the urban water system.

 

Bar graph of annual surface water allocation and diversion for different users in the Melbourne region from 2012–13 to 2020–21. Most of the surface water allocations are associated with the urban system. Allocations for the urban system were much higher than the previous few years. In 2020–21, 36% of the allocation for the urban system was taken, lower than the previous year. 38% of the allocation for individual users was taken. 70% of the allocation for inter-region supply was taken. Non-allocated surface water is also taken for individual users.
Figure S6 Surface water allocations and diversions in the Melbourne region for the years ending 30 June, from 2012–2021

 

  • In 2020–21, total surface water allocation was 881 GL, mostly for urban system supply. 37% of the allocated surface water was taken.
  • Allocations for the urban system decreased by 6% from the previous year.
  • Actual diversions to the urban system were much lower than previous years. The lower surface water supply was influenced by the Melbourne Water Corporation opting to reduce pressure on its surface water resources and increase its reliance on desalinated water to meet urban demand (see Urban system supply section below).
  • Total diversions to individual users (allocated and non-allocated) were similar to last year.

 

Bar graph of annual groundwater allocation and extraction for different users in the Melbourne region from 2012–13 to 2020–21. Most of the groundwater allocations are associated with individual users. The allocation in 2020–21 was similar to the previous few years. In 2020–21, 26% of the allocation for individual users was taken, similar to the previous few years. 5% of the allocation for the urban system was taken.
Figure S7 Groundwater allocations and extractions in the Melbourne region for the years ending 30 June, from 2012–2021

 

  • Total groundwater allocation was 69 GL, mostly for agricultural purposes. 25% of the allocated groundwater was taken.
  • Allocated extractions for both individual users and the urban water system were similar to last year. Urban supply in particular has changed little over the last few years.

 

Urban system supply

Stacked bar graph showing the annual water sourced for Melbourne region's urban supply system during the period from 2010–11 to 2020–21. Each bar in the stack progressively represents surface water, groundwater, and desalinated water. Between 2010–11 and 2016–17 there was a general increasing trend in total water sourced for the urban system. Since 2016–17, there have been three 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 4 years. Key aspects of the graph are described in the text below the figure.
Figure S8 Water sources used in the Melbourne region's urban supply system during the 2020–21 year compared with the previous ten years

 

  • Total inflows to the water supply system was 440 GL, about 4% less than last year.
  • 72% of the total urban supply was from surface water storages. Desalinated water made up 28% of urban supply while less than 1% was from groundwater extractions.
  • The contribution of desalinated water to urban supply was the highest it's ever been. The Melbourne Water Corporation opted to increase its reliance on desalinated water in 2019–20 following the very dry conditions in the previous year and further increased it in 2020–21.

 

Water market activity

Werribee South coastline (istock © Greg Brave)

 

Table S3 Water trade in the Melbourne region during the 2020–21 year
Transaction typeNumber of transactionsVolume (ML)
Surface water transactions  
Entitlement trades793
Allocation trades24746
Permanent trade of take-and-use licences21314
Temporary trade of take-and-use licences25848
Groundwater transactions  
Permanent trade of take-and-use licences*271,438
Temporary trade of take-and-use licences*22933

* Excludes any trade within unincorporated areas

 

  • Entitlement and allocation trades and lease (term transfers) of water shares, and temporary and permanent trade of take-and-use licences are allowed in the Melbourne region.
  • More information about water trading in the Melbourne region is available from the Bureau's Water Market Dashboard and the Victorian Water Register.

 

Cultural and environmental water

Yarra River at Warrandyte, Melbourne region (Alison Pouliot © 2010)

 

Cultural benefits

  • In general, water regimes required to support cultural values are not quantitatively defined in water allocation plans; however, the cultural values are considered within the environmental water provisions.
  • More information on cultural water requirements are provided in the Cultural water management section in the 'Region description'.

 

Environmental benefit

Environmental water management scenarios

  • In the Melbourne region, environmental water is provided according to the scenarios: held environmental water, planned and partly regulated surface water, and planned and unregulated surface water.

 

Environmental entitlements: held environmental water

  • The Victorian Environmental Water Holder holds three environmental water entitlements: Consolidated Yarra Environmental Entitlement 2006 (revised in July 2014), Tarago and Bunyip Rivers Environmental Entitlement 2009 (revised in June 2014), and Werribee River Environmental Entitlement 2011.
  • These entitlements prescribe environmental flow regimes in respective rivers including the characteristics of recommended environmental flows for the river reaches.
  • In 2020–21, 10,577 ML of water was released by Melbourne Water to meet the region's ecological objectives in the Yarra, Tarago, and Werribee rivers (see figure below).

 

Map of environmental releases in the 4 major river systems. 739 ML of water was released to the environment from Werribee River, in the southwest of the region. 0 ML was released from the Maribyrnong River in the region's northwest. 8,504 ML was released from the Yarra River in the region's northeast. 1,334 ML was released from Tarago River in the region's southeast.
Figure S9 Delivery of held environmental water in each river system within the Melbourne region

 

Bulk entitlements

  • Bulk entitlements with the provisions for planned partly regulated surface water are: Southern Rural Water's bulk entitlement to the Maribyrnong River, Western Water's bulk entitlement to the Maribyrnong River, and Melbourne Water's bulk entitlement to the Maribyrnong, Bunyip and Tarago rivers.
  • Bulk entitlements with the provisions for planned unregulated surface water are: Southern Rural Water's bulk entitlement to the Werribee system for irrigation, Melbourne Water's bulk entitlement to the Yarra River, and Western Water's bulk entitlements to various sources in the Maribyrnong catchment and in the Werribee system.
  • Details of compliance with the conditions specified for the entitlement during the year, in particular the passing flows, are available in a report submitted by relevant bulk entitlement holders to the Victorian Minister for Water (this information is also typically contained in the responsible holder's annual report).

 

Streamflow management plans: planned unregulated surface water

  • In accordance with Section 32C of the Water Act, Melbourne Water, which administers streamflow management plans, must submit to the Victorian Minister for Water a report detailing its compliance with the plan during the year.
  • For more information, these reports can be found on the Melbourne Water website.