Until the outcome of the 2025 federal election, the Australian Government is operating under caretaker conventions

National Water Account 2021

Perth: Statement of Changes in Water Assets and Water Liabilities

for the year ended 30 June 2021

  • The volume of water in the region's storages increased during 2020–21 compared to last year.
  • This increase represents the change in water volume in the region's surface water storages.

Schematic representation of the Perth region. Total water inflows during 2020–21 was 2,844 GL. Total water outflows was 2,735 GL. Water storage at 30 June 2021 was 5 GL more than the previous year.

The Statement of Changes in Water Assets and Water Liabilities is provided in the table below. The statement presents the actual water flows associated with the region's water stores, as well as the changes in water assets and water liabilities that occurred during the year.

 

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  2021 ML 2020 ML 2019 ML 2018 ML 2017 ML 2016 ML
Water inflows
Surface water inflows 1,225,189 1,171,112 1,556,367 1,374,943 1,782,957 778,502
Precipitation 48,944 41,637 56,014 55,877 37,453 16,824
Runoff 811,488 653,907 938,880 749,192 840,406 352,148
Inter-region inflow 85,952 70,098 173,882 132,914 444,083 –
Flood return 175 608 710 10,674 19,919 –
Discharge: groundwater* 197,429 320,720 350,701 339,368 339,167 256,534
Discharge: urban supply* 78,559 81,395 33,797 84,496 99,858 **81,104
Riparian release: urban supply* 2,642 2,747 2,383 2,422 2,071 **2,136
 
Groundwater inflows 1,049,398 1,385,974 1,688,739 1,782,656 1,640,339 1,236,022
Inter-region inflow 43,060 48,035 48,562 **48,298 **48,348 47,475
Inter-region coastal inflow 0 0 0 0 0 0
Recharge: landscape 970,725 1,301,647 1,611,117 1,701,601 1,567,101 1,165,106
Leakage: urban system* 20,323 23,554 24,130 24,270 23,431 21,873
Managed aquifer recharge* 15,290 12,738 4,930 8,487 1,459 1,568
 
Urban water system inflows 519,733 515,221 463,014 509,463 523,017 517,538
Wastewater collected 138,664 135,791 141,684 141,185 140,439 138,858
Allocated diversion: surface water* 98,358 101,929 107,811 85,631 91,326 101,204
Allocated extraction: groundwater* 137,064 135,516 122,318 131,948 139,598 136,878
Delivery: desalinated water 143,641 140,047 89,295 148,904 **149,822 138,645
Supply system delivery: inter-region 2,006 1,938 1,906 1,795 1,832 1,953
 
Irrigation scheme inflows 49,701 73,827 74,809 72,969 59,277 69,094
Allocated diversion: surface water* 49,701 73,827 74,809 72,969 59,277 69,094
Total water inflows 2,844,021 3,146,134 3,782,929 3,740,031 4,005,590 2,601,156
Water outflows
Surface water outflows 969,475 1,013,419 1,815,011 1,619,004 1,750,060 434,481
Evaporation 61,088 62,032 73,604 57,417 48,591 28,912
Outflow 590,071 605,770 1,287,580 1,185,613 1,221,652 196,413
Leakage: landscape 150 150 150 150 150 150
River losses 118,024 111,192 144,767 114,471 238,759 –
Overbank flow 6,910 14,521 82,691 64,368 51,454 –
Allocation diversion: individual users 45,173 43,998 43,599 **38,385 38,851 38,708
Allocated diversion: urban system* 98,358 101,929 107,811 85,631 91,326 101,204
Allocated diversion: irrigation scheme* 49,701 73,827 74,809 72,969 59,277 69,094
 
Groundwater outflows 1,192,823 1,618,604 1,678,641 1,588,437 1,524,571 1,361,780
Inter-region outflow 18,070 22,034 23,128 **22,930 **22,762 21,863
Inter-region coastal outflow 222,298 299,403 **308,651 290,715 261,169 **233,290
Discharge: landscape 232,977 455,872 480,437 422,165 389,246 332,617
Discharge: surface water* 197,429 320,720 350,701 339,368 339,167 256,534
Non-allocated extraction: individual users 84,490 84,031 82,881 81,791 81,256 80,845
Allocation extraction: individual users 300,495 301,028 310,525 299,520 291,373 299,753
Allocated extraction: urban system* 137,064 135,516 122,318 131,948 139,598 136,878
 
Urban water system outflows 524,368 494,144 454,577 501,755 514,501 517,992
Supply system delivery: urban users 224,579 223,123 228,344 227,634 224,799 236,200
Recycled water delivery: urban users 8,499 7,943 6,856 4,698 8,622 9,095
Discharge: sea 119,613 112,235 123,224 118,202 119,190 123,163
Discharge: landscape 1,080 0 4,656 4,465 5,734 6,145
Supply system transfer: inter-region 44,461 21,049 17,713 18,563 20,883 27,923
Other supply system decreases 9,322 9,360 8,544 8,518 8,454 8,785
Leakage: groundwater* 20,323 23,554 24,130 24,270 23,431 21,873
Supply system discharge: reservoirs* 78,559 81,395 33,797 84,496 99,858 **81,104
Supply system discharge: riparian release* 2,642 2,747 2,383 2,422 2,071 **2,136
Managed aquifer recharge* 15,290 12,738 4,930 8,487 1,459 1,568
 
Irrigation scheme outflows 48,717 75,756 73,953 74,298 59,378 70,658
Delivery 36,832 54,233 52,777 54,060 43,457 **53,457
Leakage: landscape 11,885 21,523 21,176 20,238 15,921 **17,201
 
Total water outflows 2,735,383 3,201,923 4,022,182 3,783,494 3,848,510 2,384,911
 
Unaccounted-for difference (103,297) 501 **264,443 **136,169 **(122,076) **(288,557)
 
 
Change in water storage            
Change in surface water storage 5,341 (55,288) 25,190 92,706 35,004 **(72,312)
Change in groundwater storage – – – – – –
Total change in water storage 5,341 (55,288) 25,190 92,706 35,004 **(72,312)
 
Closing water storage 365,469 360,128 415,416 390,226 297,520 **262,516
 
 
Change in water claims            
Change in urban system claims 0 0 0 0 0 0
Change in irrigation scheme claims* (33) (8,803) 2,493 (2,940) 5,709 **(13,770)
Total change in water claims (33) (8,803) 2,493 (2,940) 5,709 **(13,770)
 
 
Change in water liability
Surface water liability (33) (8,803) 2,493 (2,940) 5,711 (13,687)
Allocation remaining: individual users 0 0 0 0 2 83
Allocation remaining: urban system* 0 0 0 0 0 0
Allocation remaining: irrigation scheme* (33) (8,803) 2,493 (2,940) 5,709 **(13,770)
 
Groundwater liability (1) 0 0 1 (4,880) (1,837)
Allocation remaining: individual users 0 0 0 1 (4,880) (1,837)
Allocation remaining: urban system* 0 0 0 0 0 0
Total change in water liability (34) (8,803) 2,493 (2,939) 831 **(15,524)
             
Net change in water assets 5342 (55,288) 25,190 92,705 39,882 **(70,558)
 

 

* between-store flows

** different to published volume in historical accounts (see Governance for more information)

Note: quantification approaches used to derive each item volume are provided in the Methods