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Melbourne: Supporting information

  • Rainfall during the 2021-22 year was above average, contributing to high runoff and storage inflows across the region. 
  • Total storage volumes increased by 12% during the 2021-22 year to finish at 87% full by 30 June 2022 - the highest end-of-year storage volume since records began in 1980.
  • 38% of surface water allocations and 29% of groundwater allocated were taken in 2021-22, primarily for individual users.

Schematic representation of the Melbourne region. In 2021–22, runoff was 4% more than average. Storage volumes at 30 June 2022 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 volume in the region at 30 June 2022 was 1,795 GL, around 96% of which was water held in surface water storages.
  • Around 2% of the water assets are held in aquifers, while the remaining 2% of water assets are part of the urban water supply system. 

 

Table S1 Accessible storage volume in the Melbourne region at 30 June 2022 compared with the previous eight years
  2022 2021 2020 2019 2018 2017 2016 2015 2014
Cardinia 235,252 207,773 208,122 171,106 169,420 189,356 181,646 166,997 184,315
Greenvale 25,433 22,564 21,716 19,476 22,957 22,641 21,501 22,354 17,479
Maroondah 12,950 21,251 22,177 8,234 12,014 8,584 10,850 13,459 9,834
Melton 12,146 14,376 10,030 5,265 3,118 7,215 815 1,197 1,118
Merrimu 23,693 14,921 10,245 10,264 11,861 16,098 2,767 9,142 19,869
O'Shannassy 3,180 3,117 2,594 309 2,696 2,538 2,340 1,892 3,239
Pykes Creek 17,322 20,371 16,344 16,368 14,751 16,209 4,127 11,005 16,228
Rosslynne 16,019 10,043 5,492 4,627 5,956 9,376 3,582 11,031 18,941
Silvan 34,980 36,656 35,551 34,200 35,664 35,154 35,954 33,996 35,668
Sugarloaf 93,011 83,417 90,115 43,672 55,561 67,004 65,789 65,220 83,867
Tarago 37,836 37,924 31,536 23,717 29,783 33,172 34,310 37,652 38,046
Thomson 962,548 789,695 638,910 492,042 607,562 644,403 597,885 770,296 812,086
Upper Yarra 138,972 128,308 79,116 95,544 96,529 97,236 101,612 100,779 105,173
Yan Yean 29,257 27,006 26,030 21,771 24,951 26,448 24,219 25,740 26,862
Accessible total 1,642,599 1,417,422 1,197,978 946,595 1,092,823 1,175,434 1,087,397 1,270,760 1,372,725
Dead storage 76,623 76,623 76,623 76,623 76,623 76,623 76,623 76,623 76,623
Total storage 1,719,222 1,494,045 1,274,601 1,023,218 1,169,446 1,252,057 1,164,020 1,347,383 1,449,348
Total capacity 1,980,744 1,980,744 1,980,744 1,980,744 1,980,744 1,980,744 1,980,744 1,980,744 1,980,744
% full 86.8% 75.4% 64.3% 51.7% 59.0% 63.2% 58.8% 68.0% 73.2%

 

  • Storage volumes increased from 75% full at 30 June 2021 to 87% full at 30 June 2022.
  • The end-of-year storage volume at 30 June 2022 was the highest since records began in 1980.

 

Map of Melbourne region showing the status of each storage at 30 June 2022. 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 2022. Melbourne storages at 30 June 2022 were 87% full, 12% higher than last year.
Figure S1 Percentage-full volume on 30 June 2022 for each storage and total storage volume from 2009–2022 (inset)

  • Storage volumes steadily rose in the first six months of the 2021-22 year following above-average rainfall, peaking at 90% during December 2021. This was the highest storage value for the Melbourne urban region since records began in 1980.
  • By the start of June 2022, storages had dipped to 83%, but above-average rainfall during June caused storages to increase and end the 2021-22 year at 86.8% full.
  • 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 2021-22 year.

 

Table S2 Volume of surface water allocation remaining at 30 June 2022
Description Surface water (ML)
  Opening balance at 1 July 2021 11,451
add Allocation 15,488
less Allocated diversion 8,311
less Adjustment and forfeiture 6,172
  Closing balance at 30 June 2022 12,456

 

Table S3 Volume of groundwater allocation remaining at 30 June 2022
Description Groundwater (ML)
  Opening balance at 1 July 2021 0
add Allocation 65,888
less Allocated extraction 18,933
less Adjustment and forfeiture 46,955
  Closing balance at 30 June 2022 0

 

Table S4 Commitment: inter-region at 30 June 2022
Description Inter-region (ML)
  Opening balance at 1 July 2021 0
add Allocation 5,292
less Allocated diversion 4,027
less Adjustment and forfeiture 1,265
  Closing balance at 30 June 2022 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 3,460 GL, 3% less than last year.
  • Surface water inflows contributed 1,757 GL (51%) of total water inflows. Runoff contributed to 82% of the total surface water inflows.
  • Groundwater inflows contributed 719 GL (21%) of total water inflows. Recharge from landscape contributed to 59% of the total groundwater inflows.
  • Urban water inflows contributed 984 GL (28%) of total water inflows. Diversion of surface water contributed to 45% of the total urban water inflows.
  • Total water outflows from the Melbourne region was 3,250 GL, 9% more than last year.
  • Surface water outflows contributed 2,281 GL (70%) of total water outflows. Outflow contributed to 59% of the total surface water outflows.
  • Groundwater outflows contributed 130 GL (4%) of total water outflows. Inter-region coastal outflow contributed to 85% of the total groundwater outflows.
  • Urban water outflows contributed 837 GL (26%) of total water outflows. Supply of drinking water to the urban users contributed to 47% 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 from 2013-14 to 2021-22
  2022 2021 2020 2019 2018 2017 2016 2015 2014
Water availability 2,955,822 2,690,797 2,914,569 1,911,680 2,215,583 2,676,479 2,169,589 2,316,670 2,829,549
Water accessible 364,100 365,144 376,208 478,359 478,550 430,035 473,532 451,950 449,452
Water taken 344,207 338,275 361,152 469,337 467,219 414,707 469,059 443,631 442,386

 

  • 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 2021–22 was above average for the third consecutive year.
  • 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 availabile. Typically, water taken from surface water resources is lower than water availability and water accessible.
  • Water taken from surface water resources increased by 18%.

 

Water use

Werribee South coastline (istock © Greg Brave)

 

Consumptive use

 

Table S6 Surface water taken for consumptive use in the Melbourne region for the previous four years
Surface water 2022 2021 2020 2019
Individual users 8,311 8,664 8,651 7,618
Urban system 320,264 315,125 337,915 443,896
Inter-region 4,027 3,647 4,263 4,171
Total 332,602 327,436 350,829 455,685

 

Table S7 Groundwater taken for consumptive use in the Melbourne region for the previous four years
Groundwater 2022 2021 2020 2019
Individual users 18,933 17,559 18,278 20,960
Urban system 60 76 72 72
Total 18,993 17,635 18,350 21,032

 

  • Water taken from surface water and groundwater resources for consumptive use was 351,595 ML.
  • Total surface water diverted in the region was 332,602 ML, a slight increase from the previous year.
  • 96% of the total surface water diverted was for urban system supply, mostly by the Melbourne Water Corporation; 3% was for individual users (comprising allocated and non-allocated diversions) while 1% was for inter-region supply.
  • Total groundwater extracted in the region was 18,933 ML.
  • More than 99% of the total groundwater extracted was for individual users; less than 1% was for the urban system supply.

 

Allocations and diversions

 

Table S8 Surface water allocations and diversions in the Melbourne region for the year ending 30 June
Surface water 2022 2021 2020 2019
Individual users
Carryover 11,451 11,229 5,958 8,408
Allocated announcements 15,488 22,726 16,787 6,978
Allocated diversions 8,311 8,664 8,651 7,618
% used 31% 26% 38% 50%
Inter-region
Carryover 0 0 0 0
Allocated announcements 5,292 5,225 5,225 5,425
Allocated diversions 4,027 3,647 4,263 4,171
% used 76% 70% 82% 77%

 

  • In 2021-22, total surface water allocated plus carryover for individual users was 32,231 ML (26,939 ML for individual users and 5,292 ML for inter-region).
  • Overall, 38% of the allocated plus carryover surface water was taken (31% of individual users and 76% inter-region).
  • Total allocated diversions to individual and inter-region users of 12,338 ML were similar to last year's allocated diversions of 12,311 ML.

 

Table S9 Groundwater allocations and diversions in the Melbourne region for the year ending 30 June
Groundwater 2022 2021 2020 2019
Individual users
Carryover - - - -
Allocated announcements 65,888 67,986 65,051 64,628
Allocated extractions 18,933 17,559 18,278 20,960
% used 29% 26% 28% 32%

 

  • In 2021-22, total groundwater allocated was 65,888 ML.
  • 29% of the allocated groundwater was taken.
  • Allocated extractions for individual users was slightly more compared to last year.

 

Urban supply system

 

Table S10 Water sources used in the Melbourne's urban supply system over the previous ten year
  2022 2021 2020 2019 2018 2017 2016 2015 2014 2013 2012
Surface water 320,264 315,125 337,915 443,896 443,736 390,639 445,845 419,917 415,334 408,812 374,198
Groundwater 60 76 72 72 72 60 102 86 102 66 0
Desalinated water 125,000 125,000 118,132 22,374 14,972 46,209 0 0 0 0 0
Total urban water supplied 445,324 440,201 456,119 466,342 458,780 436,908 445,947 420,003 415,436 408,878 374,198

 

  • Total inflows into the urban supply system was 445,324 ML, slightly more than last year but still less when compared to 2018 to 2020.
  • Around 72% of the total urban supply was from surface water storages. Desalinated water made up roughly 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; equal to last year. 
  • For more information on the use of desalinated water for the Melbourne region, please visit Melbourne Water Corporation's Desalinated webpage.