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Melbourne: Supporting information

For the water account period 01 July 2022 - 30 June 2023

  • Total annual rainfall was above average for the fourth consecutive year, with the region experiencing its wettest year since 2010-11, contributing to high runoff and storage inflows across the region. 
  • End-of-year storage volume increased by five percentage points, finishing at 92% full by 30 June 2023 - the highest end-of-year storage volume for the region on record.
  • Approximately, 36% of surface water allocations and 52% of groundwater allocated were taken in 2022-23, primarily for individual users.

Schematic representation of the Melbourne region. In 2022-23, runoff was 68% more than average. Storage volumes on 30 June 2023 were 92% full, 5% higher than the previous year. 98% of the total surface water accessible (488 GL) was taken. 29% of the total groundwater accessible (66 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 on 30 June 2023 were 1,902 GL, 96% of which was held in surface water storages.
  • Around 2% of the water assets are held in aquifers, while slightly less than 2% of water assets are part of the urban water supply system.
  • Less than 1% of the region's total water assets are held in rivers.

 

Table S1 Accessible storage volume in the Melbourne region over the past six water accounting periods ending 30 June
 Surface water 2023 2022 2021 2020 2019 2018
Cardinia 247,580 235,252 207,773 208,122 171,106 169,420
Greenvale 23,585 25,433 22,564 21,716 19,476 22,957
Maroondah 22,470 12,950 21,251 22,177 8,234 12,014
Melton 11,036 12,146 14,376 10,030 5,265 3,118
Merrimu 28,742 23,693 14,921 10,245 10,264 11,861
O'Shannassy 3,250 3,180 3,117 2,594 309 2,696
Pykes Creek 19,666 17,322 20,371 16,344 16,368 14,751
Rosslynne 23,886 16,019 10,043 5,492 4,627 5,956
Silvan 35,525 34,980 36,656 35,551 34,200 35,664
Sugarloaf 93,545 93,011 83,417 90,115 43,672 55,561
Tarago 37,918 37,836 37,924 31,536 23,717 29,783
Thomson 1,032,372 962,548 789,695 638,910 492,042 607,562
Upper Yarra 135,057 138,972 128,308 79,116 95,544 96,528
Yan Yean 29,151 29,257 27,006 26,030 21,771 24,950
Accessible total 1,743,783 1,642,599 1,417,422 1,197,978 946,595 1,092,821
Dead storage 76,623 76,623 76,623 76,623 76,623 76,623
Total storage 1,820,406 1,719,222 1,494,045 1,274,601 1,023,218 1,169,444
Total capacity 1,980,744 1,980,744 1,980,744 1,980,744 1,980,744 1,980,744
% full 91.9% 86.8% 75.4% 64.3% 51.7% 59.0%

 

  • Storage volume increased from 86.8% full at 30 June 2022 to 91.9% full at 30 June 2023 - an increase of 5.1%.
  • This is the highest end-of-year storage volume for the region on record, surpassing last year's end-of-year storage volume of 86.8%

 

Map of Melbourne region showing the status of each storage at 30 June 2023. The storages are colour coded into eleven categories of volume as a proportion of capacity. An inset line graph shows the time series of percentage-full storage volume between 01 July 2009 – 30 June 2023. Melbourne storages on 30 June 2023 were 92% full, 6% higher than last year.
Figure S1 Percentage-full volume on 30 June 2023 for each storage and total storage volume from 2009–2023 (inset)

  • Storage volumes steadily rose in the first six months of the 2022-23 year following the region's third-wettest spring on record, peaking at 98% full during November. This was the highest storage value for the Melbourne urban region since storage records began back in 1980, surpassing last year's value of 90% full in December 2021.
  • Following average to below-average rainfall from December 2022 onwards, the region's storage gradually dropped through to the end of June 2023, with the region's end-of-year storage volume sitting at 91.9% full on 30 June 2023.
  • 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 2022-23 year.

 

Table S2 Opening and closing balance of surface water allocations for individual users in the Melbourne region over the past six water accounting periods
Description 2023 2022 2021 2020 2019 2018
Opening balance at 01 July 12,456 11,451 11,229 5,958 8,408 10,995
add Allocation 16,000 15,488 22,726 16,787 6,978 6,351
less Allocated diversion 8,300 8,311 8,664 8,651 7,618 7,391
less Adjustment and forfeiture 8,000 6,172 13,840 2,865 1,810 1,547
Closing balance at 30 June 12,156 12,456 11,451 11,229 5,958 8,408

 

Table S3 Opening and closing balance of groundwater allocations for individual users in the Melbourne region over the past six water accounting periods
Description 2023 2022 2021 2020 2019 2018
Opening balance at 01 July 0 0 0 0 0 0
add Allocation 66,100 65,888 67,986 65,051 64,628 67,816
less Allocated extraction 19,030 18,933 17,559 18,278 20,960 21,010
less Adjustment and forfeiture 47,070 46,955 50,427 46,773 43,668 46,806
Closing balance at 30 June 0 0 0 0 0 0

 

Table S4 Opening and closing balance of inter-region commitments in the Melbourne region over the past six water accounting periods
Description 2023 2022 2021 2020 2019 2018
Opening balance at 01 July 0 0 0 0 0 0
add Allocation 5,300 5,292 5,225 5,225 5,425 5,225
less Allocated diversion 4,000 4,027 3,647 4,263 4,171 3,849
less Adjustment and forfeiture 1,300 1,265 1,578 962 1,254 1,376
Closing balance at 30 June 0 0 0 0 0 0

 

  • 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

Yarra River Weir (Alison Pouliot @ 2010)

 

  • Total water inflows into the Melbourne region was 4,301 GL, 29% more than last year.
  • Surface water inflows contributed 2,774 GL (64%) of total water inflows, with runoff accounting for 85% of the total surface water inflows.
  • Groundwater inflows contributed 798 GL (19%) of total water inflows, with recharge from landscape accounting for 54% of the total groundwater inflows.
  • Urban water inflows contributed 728 GL (17%) of total water inflows, with diversion of surface water accounting for 62% of the total urban water inflows.
  • Total water outflows from the Melbourne region was 4,676 GL, 43% more than last year.
  • Surface water outflows contributed 3,692 GL (79%) of total water outflows, with outflow to sea accounting for 63% of the total surface water outflows.
  • Groundwater outflows contributed 129 GL (3%) of total water outflows, with inter-region coastal outflow accounting for 85% of the total groundwater outflows.
  • Urban water outflows contributed 854 GL (18%) of total water outflows, with discharge to sea accounting for 43% of the total urban water outflows.
  • A more detailed breakdown of inflows and outflows is given in the Statement of Changes in Water Assets and Water Liabilities for the Melbourne region.

 

Water availability

 

Table S5 Annual surface water available in the Melbourne region over the past six water accounting periods ending 30 June
Surface water 2023 2022 2021 2020 2019 2018
Water availability 4,108,191 2,957,491 2,693,921 2,915,566 1,913,296 2,216,849
Water accessible 488,206 477,648 478,915 488,382 492,325 482,627
Water taken 479,206 469,206 463,275 479,284 491,711 482,191
% water accessible taken 98% 98% 97% 98% 100% 100%

 

  • Physical surface water availability is calculated as the sum of storage volumes at the start of the year (see Water assets) and estimated inflows into storages and rivers during the year.
  • Surface water availability in the Melbourne region in 2022-23 was the highest on record, following the region's fourth consecutive year of above-average rainfall.
  • Surface water accessible is calculated as the sum of surface water allocations and other statutory rights, plus carryover at the start of the year.
  • Water taken during the year is influenced by the physical water available. Typically, water taken from surface water resources is lower than water availability and water accessible.
  • Despite an increase in physical surface water availability, water accessible and water taken from surface water resources remained close to average.

 

Water use

Werribee South coastline (istock © Greg Brave)

 

Consumptive use

 

Table S6 Surface water taken for consumptive use in the Melbourne region over the past six water accounting periods ending 30 June
Surface water 2023 2022 2021 2020 2019 2018
Individual users 8,300 8,311 8,664 8,651 7,618 7,391
Urban system 455,286 455,263 440,125 456,047 466,270 458,708
Inter-region 4,000 4,027 3,647 4,263 4,171 3,849
Total 467,586 457,601 452,436 468,961 478,059 469,948

 

Table S7 Groundwater taken for consumptive use in the Melbourne region over the past six water accounting periods ending 30 June
Groundwater 2023 2022 2021 2020 2019 2018
Individual users 19,030 18,933 17,559 18,278 20,960 21,010
Urban system 81 61 76 72 73 72
Total 19,111 18,994 17,635 18,350 21,033 21,082

 

  • Water taken from surface water and groundwater resources for consumptive use was 486,697 ML, slightly more than last year.
  • Total surface water diverted in the region was 467,586 ML, a slight increase from the previous year.
  • 97% of the total surface water diverted was for urban system, mostly by the Melbourne Water Corporation; 2% was for individual users (comprising allocated and non-allocated diversions) while 1% was for inter-region supply.
  • Total groundwater extracted in the region was 19,111 ML, a slight inrease from the previous year.
  • More than 99% of the total groundwater extracted was for individual users. The remaining amount of groundwater extracted was for the urban system.

 

Allocations and diversions

 

Table S8 Surface water allocations and diversions in the Melbourne region over the past six water accounting periods ending 30 June
Surface water 2023 2022 2021 2020 2019 2018
Individual users
Carryover 12,456 11,451 11,229 5,958 8,408 10,995
Allocated announcements 16,000 15,488 22,726 16,787 6,978 6,351
Allocated diversions 8,300 8,311 8,664 8,651 7,618 7,391
% used 29% 31% 26% 38% 50% 43%
Inter-region
Carryover 0 0 0 0 0 0
Allocated announcements 5,300 5,292 5,225 5,225 5,425 5,225
Allocated diversions 4,000 4,027 3,647 4,263 4,171 3,849
% used 75% 76% 70% 82% 77% 74%
Total
Carryover 12,456 11,451 11,229 5,958 8,408 10,995
Allocated announcements 21,300 20,780 27,951 22,012 12,403 11,576
Allocated diversions 12,300 12,338 12,311 12,914 11,789 11,240
% used 36% 38% 31% 46% 57% 50%

 

  • Total surface water allocated in the region during 2022-23 was 33,756 ML (28,456 ML for individual users and 5,300 ML for inter-region).
  • Overall, 36% of the allocated surface water was taken (29% of individual users and 75% inter-region). This was similar to last year, and close to the average for the region.

 

Table S9 Groundwater allocations and extractions for individual users in the Melbourne region over the past six water accounting periods ending 30 June
Groundwater 2023 2022 2021 2020 2019 2018
Individual users
Carryover - - - - - -
Allocated announcements 16,000 15,488 22,726 16,787 6,978 6,351
Allocated extractions 8,300 8,311 8,664 8,651 7,618 7,391
% used 52% 54% 38% 52% 109% 116%

 

  • Total groundwater allocated in the region during 2022-23 was 16,000 ML, all for individual users. This was similar to last year, but less than the average.
  • Around 52% of the allocated groundwater was taken, which was similar to last year, and close to the average for the region.

 

Urban supply system

 

Table S10 Water sources used in Melbourne's urban supply system over the past six water accounting periods ending 30 June
Water sources 2023 2022 2021 2020 2019 2018
Surface water 455,286 445,263 440,125 456,047 466,270 458,708
Groundwater 81 61 76 72 73 72
Desalinated water 4,182 125,000 125,000 118,132 22,374 14,972
Total urban water supplied 459,549 570,324 565,201 574,251 488,717 473,752

 

  • Total inflows into the urban supply system was 459,549 ML, 19% less than last year, but close to the long-term average.
  • Around 99% of the total urban supply was from surface water storages. The remaining amount of water sourced in the urban supply system was from groundwater extractions and desalinated water.
  • The decrease in supply of desalinated water to the region's urban supply system was due to low demand, following a sufficient amount of surface water available within the region.
  • For more information on the use of desalinated water for the Melbourne region, please visit Melbourne Water Corporation's Desalinated webpage.