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Perth: Statement of Changes in Water Assets and Water Liabilities

for the year ended 30 June 2022

  • The volume of water in the region's storages increased during 2021–22 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 2021–22 was 4,785 GL. Total water outflows was 4,577 GL. Water storage at 30 June 2022 was 106 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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  2022 (ML) 2021 (ML) 2020 (ML) 2019 (ML) 2018 (ML) 2017 (ML)
Water inflows
Surface water inflows 2,602,918 1,177,353 1,138,639 1,794,267 2,044,955 1,883,524
Precipitation on storages 42,000 28,617 24,699 29,521 55,877 37,453
Precipitation on rivers 34,984 20,231 16,674 26,134 35,121 23,911
Runoff 1,644,669 768,124 621,491 1,175,408 1,389,866 941,801
Flood return
10,845 312 614 2,441 4,858 1,024
Urban water return* 61,465 78,559 81,758 33,797 84,496 99,858
Inflow from outside region 529,797 81,439 69,936 173,882 132,947 438,239
Discharge from groundwater* 276,504 197,429 320,720 350,701 339,368 339,167
Riparian release from urban water system* 2,654 2,642 2,747 2,383 2,422 2,071
 
Groundwater inflows 1,602,735 1,085,086 1,425,489 1,731,918 1,820,501 1,679,357
Inter-region inflow 43,153 43,060 48,035 48,562 48,298 48,348
Inter-region coastal inflow 37,915 35,688 39,515 43,179 37,845 39,018
Recharge from landscape 1,479,365 970,725 1,301,647 1,611,117 1,701,601 1,567,101
Leakage from urban water system* 27,278 20,323 23,554 24,130 24,270 23,431
Managed aquifer recharge from urban system* 15,024 15,290 12,738 4,930 8,487 1,459
 
Urban water system inflows 512,911 519,733 515,221 463,014 509,463 523,017
Wastewater collected 143,135 138,664 135,791 141,684 141,185 140,439
Diversion of surface water* 121,326 98,358 101,929 107,811 85,631 91,326
Extraction of groundwater* 130,256 137,064 135,516 122,318 131,948 139,598
Delivery of desalinated water 116,135 143,641 140,047 89,295 148,904 149,822
Inter-region delivery to the urban system* 1,996 2,006 1,938 1,906 1,795 1,832
 
Irrigation scheme inflows 66,112 49,701 73,827 74,809 72,969 59,277
Allocated diversion from irrigation scheme* 66,112 49,701 72,827 74,809 72,969 59,277
Total water inflows 4,784,676 2,831,873 3,153,176 4,064,009 4,447,888 4,145,175
Water outflows
Surface water outflows 2,504,543 979,485 1,008,227 1,794,899 1,737,459 1,591,225
Evaporation from storages 59,699 40,873 42,685 49,408 57,417 48,591
Evaporation from rivers 22,820 18,381 17,579 20,204 21,885 21,659
Outflow 1,910,772 617,501 617,596 1,280,713 1,2264,723 1,154,202
Leakage to landscape 150 150 150 150 150 150
River losses 146,407 96,464 91,363 133,911 125,911 114,294
Overbank flow 133,164 12,884 19,100 84,294 70,388 62,874
Allocated diversion to individual users 44,093 45,173 43,998 43,599 38,385 38,851
Diversion to the urban system* 121,326 98,358 101,929 107,811 85,631 91,326
Allocated diversion to irrigation scheme* 66,112 49,701 73,827 74,809 72,969 59,277
 
Groundwater outflows 1,489,138 1,228,511 1,654,758 1,718,382 1,622,875 1,560,176
Inter-region outflow 19,196 18,070 18,671 19,690 19,524 **19,350
Inter-region coastal outflow 319,566 257,968 338,920 351,830 328,559 300,186
Discharge to landscape 354,819 232,977 455,872 480,437 422,165 389,246
Discharge to surface water* 276,504 197,429 320,720 350,701 339,368 339,167
Non-allocated extraction to individual users 84,780 84,490 84,031 82,881 81,791 81,256
Allocation extraction to individual users 304,017 300,495 301,028 310,525 299,520 291,373
Extraction to the urban system* 130,256 137,064 135,516 122,318 131,948 139,598
 
Urban water system outflows 517,140 525,139 496,644 454,496 501,662 514,410
Supply of drinking water to urban users 228,198 224,458 224,317 228,243 227,541 224,708
Supply of drinking water for own use 985 892 975 - - -
Supply of recycled water to urban users 4,361 5,132 5,366 4,611 3,213 5,780
Supply of recycled water for own use 2,789 3,367 2,545 2,265 1,485 2,842
Discharge to sea 124,616 119,613 112,235 123,224 118,202 119,190
Urban discharge to landscape 1,045 1,080 - 4,656 4,465 5,734
Supply system transfer: inter-region 40,178 44,461 21,049 17,713 18,563 20,883
Other losses 8,547 9,322 9,360 8,544 8,518 8,454
Leakage to groundwater* 27,278 20,323 23,554 24,130 24,270 23,431
Return to surface water* 61,465 78,559 81,758 33,797 84,496 99,858
Riparian release* 2,654 2,642 2,747 2,383 2,422 2,071
Managed aquifer recharge* 15,024 15,290 12,738 4,930 8,487 1,459
 
Irrigation scheme outflows 66,142 48,717 75,756 73,953 74,298 59,378
Irrigation delivery 47,947 36,832 54,233 52,777 54,060 43,457
Leakage to landscape from irrigation 18,195 11,885 21,523 21,176 20,238 15,921
 
Total water outflows 4,576,963 2,781,852 3,235,385 4,041,730 3,936,294 3,725,188
 
Unaccounted-for difference (101,854) (44,371) 25358 3,392 (419,273) (386,300)
 
 
Change in water storage            
Change in surface water storage 105,859 5,650 (56,851) 25671 92,321 33,687
Change in groundwater storage - - - - - -
Total change in water storage 105,859 5,650 (56,851) 25,671 92,321 33,687
 
Closing water storage 471,635 365,776 360,126 416,977 391,306 298,985
 
 
Change in non-physical irrigation water assets            
Change in water claims (1,934) (33) (8,803) 2,493 (2,940) 5,709
Claims: surface water* (1,934) (33) (8,803) 2,493 (2,940) 5,709
Total change in water claims (1,934) (33) (8,803) 2,493 (2,940) 5,709
 
 
Change in water liability
Surface water liability (447) (33) (8,803) 2,493 (2,940) 5,711
Allocation remaining: individual users 1,487 - - - - 2
Allocation remaining: irrigation scheme* (1,934) (33) (8,803) 2,493 (2,940) 5,709
 
Groundwater liability (24) (1) - - 1 (4,880)
Allocation remaining: individual users (24) (1) - - 1 (4,880)
Total change in water liability (471) (34) (8,803) 2,493 (2,939) 831
             
Net change in water assets 104,396 5,651 (56,851) 25,671 92,320 38,565

* between-store flows

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