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Perth: Statement of Changes in Water Assets and Water Liabilities

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

  • The volume of water in the region's storages decreased during 2022-23 compared to last year.
  • This decrease represents the change in water volume in the region's surface water storages.

Schematic representation of the Perth region. Total water inflows during 2022–23 was 3,811 GL. Total water outflows was 3,948 GL. Water storage at 30 June 2023 was 32 GL less 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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  2023 (ML) 2022 (ML) 2021 (ML) 2020 (ML) 2019 (ML) 2018 (ML)
Water inflows
Surface water inflows 1,892,779 2,601,449 1,182,586 1,143,899 1,797,814 2,026,409
Precipitation on storages 39,028 41,997 34,506 29,953 35,451 37,331
Precipitation on rivers 26,786 35,006 20,275 16,674 26,134 35,121
Runoff 1,137,041 1,642,152 767,425 621,491 1,175,408 1,389,866
Flood return
2,173 11,881 311 614 2,441 4,858
Urban water return* 55,800 64,119 81,201 84,511 33,797 86,918
Inflow from outside region 367,067 529,790 81,439 69,936 173,882 132,947
Discharge from groundwater* 264,884 276,504 197,429 320,720 350,701 339,368
 
Groundwater inflows 1,352,419 1,602,735 1,085,086 1,425,489 1,731,918 1,820,501
Inter-region inflow 39,071 43,153 43,060 48,035 48,562 48,298
Inter-region coastal inflow 37,706 37,915 35,688 39,515 43,179 37,845
Recharge from landscape 1,250,579 1,479,365 970,725 1,301,647 1,611,117 1,701,601
Leakage from urban water system* 25,063 27,278 20,323 23,554 24,130 24,270
Managed aquifer recharge from urban system* 0 15,024 15,290 12,738 4,930 8,487
 
Urban water system inflows 498,654 512,911 519,733 515,221 463,015 509,463
Wastewater collected 145,146 143,135 138,664 135,791 141,685 141,185
Delivery of desalinated water 94,474 116,198 143,641 140,047 89,295 148,904
Diversion of surface water* 120,264 121,326 98,358 101,929 107,811 85,631
Extraction of groundwater* 136,790 130,256 137,064 135,516 122,318 131,948
Inter-region delivery to the urban system 1,980 1,996 2,006 1,938 1,906 1,795
 
Irrigation scheme inflows 67,000 66,112 49,701 73,827 74,809 72,969
Allocated diversion from irrigation scheme* 67,000 66,112 49,701 73,827 74,809 72,969
 
Total water inflows 3,810,852 4,783,207 2,837,106 3,158,436 4,067,556 4,429,342
Water outflows
Surface water outflows 1,921,534 2,527,837 994,997 1,018,815 1,801,180 1,728,791
Evaporation from storages 58,458 59,700 51,097 53,273 55,689 48,749
Evaporation from rivers 20,632 22.806 18,373 17,579 20,204 21,885
Outflow to sea 1,395,887 1,930,392 622,272 617,596 1,280,713 1,264,723
Leakage to landscape 150 150 150 150 150 150
River losses 123,625 147,135 96,770 91,363 133,911 125,911
Overbank flow 92,202 136,123 13,103 19,100 84,294 70,388
Allocated diversion to individual users 44,325 44,093 45,173 43,998 43,599 38,385
Diversion to the urban system* 120,264 121,326 98,358 101,929 107,811 85,631
Allocated diversion to irrigation scheme* 65,991 66,112 49,701 73,827 74,809 72,969
 
Groundwater outflows 1,476,835 1,489,138 1,228,511 1,658,121 1,721,820 1,626,281
Inter-region outflow 19,767 19,196 18,070 22,034 23,128 22,930
Inter-region coastal outflow 319,000 319,566 257,986 338,920 351,830 328,559
Discharge to landscape 347,889 354,819 232,977 455,872 480,437 422,165
Discharge to surface water* 264,884 276,504 197,429 320,720 350,701 339,368
Non-allocated extraction to individual users 85,005 84,780 84,490 84,031 82,881 81,791
Allocation extraction to individual users 302,700 304,017 300,495 301,028 310,525 299,520
Extraction to the urban system* 136,790 130,256 137,064 135,516 122,318 131,948
 
Urban water system outflows 483,690 517,270 524,368 512,353 452,194 501,755
Leakage to groundwater* 25,063 27,278 20,323 23,554 24,130 24,270
Return to surface water* 55,800 64,119 81,201 84,511 33,797 86,918
Supply of drinking water to residential customers 185,027 184,673 182,236 180,494 182,135 180,424
Supply of drinking water to commercial and industrial customers 26,605 26,397 25,862 25,709 27,849 28,582
Supply of drinking water to agriculture and irrigation customers 80 130 121 93 101 93
Supply of drinking water to other customers 16,611 17,128 16,360 18,114 18,259 18,535
Supply of drinking water for own use 1,050 985 892 975 0 0
Supply of drinking water to other region 34,257 40,178 44,461 37,602 17,713 18,563
Supply of recycled water to commercial and industrial customers 4,197 4,361 5,132 5,366 4,611 3,213
Supply of recycled water to agriculture and irrigation customers 0 0 0 32 0 0
Supply of recycled water for own use 2,538 2,789 3,367 2,545 2,545 1,485
Treated wastewater discharge to the sea 122,846 124,616 119,613 112,235 123,224 118,202
Treated wastewater discharge to landscape 1,064 1,045 1,080 0 4,656 4,465
Managed aquifer recharge* 0 15,024 15,290 12,738 4,930 8,487
Other losses 8,552 8,547 8,430 8,385 8,544 8,518
 
Irrigation scheme outflows 66,300 66,142 48,717 75,756 73,953 74,298
Irrigation delivery 48,300 47,947 36,832 54,233 52,777 54,060
Leakage to landscape from irrigation 18,000 18,195 11,885 21,523 21,176 20,238
 
Total water outflows 3,948,359 4,600,387 2,796,593 3,265,045 4,049,147 3,931,125
 
Unaccounted-for difference 105,731 (76,656) (35,178) 49,758 7,262 (405,895)
 
 
Change in water storage            
Change in surface water storage (31,776) 106,164 5,335 (56,851) 25,671 92,322
Change in groundwater storage - - - - - -
Total change in water storage (31,776) 106,164 5,335 (56,851) 25,671 92,322
 
Closing water storage 439,849 471,625 365,461 360,126 416,977 391,306
 
 
Change in non-physical irrigation water assets            
Claims: surface water* (3,000) (1,934) (33) (8,803) 2,493 (2,940)
Total change in water claims (3,000) (1,934) (33) (8,803) 2,493 (2,940)
 
 
Change in water liability
Surface water liability (1,491) (447) (33) (8,803) 2,493 (2,940)
Allocation remaining: individual users 0 1,487 0 0 0 0
Allocation remaining: irrigation scheme* (1,491) (1,934) (33) (8,803) 2,493 (2,940)
 
Groundwater liability 1,830 (24) (1) 0 0 1
Allocation remaining: individual users 1,830 (24) (1) 0 0 1
Total change in water liability 339 (471) (34) (8,803) 2,493 (2,939)
             
Net change in water assets (35,115) 104,701 5,336 (56,851) 25,671 92,321

* between-store flows

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