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Perth: Statement of Changes in Water Assets and Water Liabilities

For the water account period 1 July 2024 to 30 June 2025

  • The volume of water in Perth's storages increased by 9 GL during 2024–25.
  • This increase represents the change in water volume in the region's surface water storages.

Schematic representation of the water flows associated with the Perth region's water stores, as well as the change to the region's water storage during the current reporting period.

The Statement of Changes in Water Assets and Water Liabilities provides a detailed breakdown of the actual water flows associated with the Perth region's water stores over the past six water accounting periods ending 30 June, as well as the changes in water assets and water liabilities that occurred during each reporting period.

To view the Statement of Changes in Water Assets and Water Liabilities, scroll down to the table below.

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 2025 (ML)2024 (ML)2023 (ML)2022 (ML)2021 (ML)2020 (ML)
Water inflows
Surface water inflows 1,156,8451,117,2701,931,6832,600,9181,182,5861,143,930
Precipitation on storages31,15025,59039,09141,99734,50629,984
Precipitation on rivers22,73415,85426,80934,99520,27516,674
Runoff932,461654,5421,137,9881,641,634767,425621,491
Flood return3,7801,4462,17411,879311614
Inflow from outside the region95,59374,290367,112529,79081,43969,936
Urban water return*71,12785,46855,80064,11981,20184,511
Discharge from groundwater***259,450302,709276,504197,429320,720
 
Groundwater inflows 48,4441,211,0531,659,9611,602,7351,085,0861,425,489
Leakage from urban water system*27,31026,11625,06327,27820,32323,554
Managed aquifer recharge by urban system*21,13416,49914,35115,02415,29012,738
Inter-region coastal inflow**45,55935,04737,91535,68839,515
Inter-region inflow**44,58543,96443,15343,06048,035
Recharge from landscape**1,078,2941,541,5361,479,365970,7251,301,647
 
Urban water system inflows556,224556,194498,654512,911519,733515,221
Delivery of desalinated water141,233119,54794,474116,198143,641140,047
Diversion of surface water*113,911136,511120,264121,32698,358101,929
Extraction of groundwater*148,739149,929136,790130,256137,064135,516
Inter-region delivery to the urban system2,1192,2611,9801,9962,0061,938
Wastewater collected150,222147,946145,146143,135138,664135,791
 
Irrigation scheme inflows46,52067,86665,99166,11249,70173,827
Irrigation allocated diversion from surface water*46,52067,86665,99166,11249,70173,827
 
Total water inflows1,808,0332,952,3834,156,2894,782,6762,837,1063,158,467
Water outflows
Surface water outflows1,393,2501,015,7221,796,0522,382,438898,237929,872
Evaporation from storages55,24458,13358,45859,70051,10755,693
Evaporation from rivers19,59417,83920,63922,82818,37317,579
Leakage to landscape150150150150150150
Outflow to sea975,343656,2191,394,1451,932,079622,272617,596
Overbank flow63,97628,60892,080136,15013,10319,100
River losses------
Allocated diversion to individual users118,51250,39644,32544,09345,17343,998
Allocated diversion to irrigation scheme*46,52067,86665,99166,11249,70173,827
Diversion to the urban system*113,911136,511120,264121,32698,358101,929
 
Groundwater outflows 770,2321,622,5921,527,1191,489,1381,228,5111,658,121
Non-allocated extraction to individual users94,000108,50786,14284,78084,49084,031
Allocated extraction to individual users527,493332,000302,700304,017300,495301,028
Extraction to the urban system*148,739149,929136,790130,256137,064135,516
Discharge to landscape**447,826354,339354,819232,977455,872
Discharge to surface water***259,450302,709276,504197,429320,720
Inter-region coastal outflows**305,992324,966319,566257,986338,920
Inter-region outflows**18,88819,47319,19618,07022,034
 
Urban water system outflows561,671566,979484,446517,270524,368517,305
Discharge to sea125,370127,660122,846124,616119,613112,235
Leakage to groundwater*27,31026,11625,06327,27820,32323,554
Managed aquifer recharge*21,13416,49914,35115,02415,29012,738
Other losses9,4879,5128,5528,5478,4308,385
Return to surface water*71,12785,46855,80064,11981,20184,511
Supply of drinking water to urban customers257,676256,998229,373229,313225,471225,385
Supply of drinking water to other regions41,52537,50534,25740,17844,46137,602
Supply of recycled water to urban customers6,9956,1707,4917,1508,4997,943
Urban discharge to landscape1,0471,0511,0641,0451,0804,952
 
Irrigation scheme outflows46,51877,48466,30066,14248,71775,756
Irrigation delivery46,51859,48448,30047,94736,83254,233
Leakage to landscape from irrigation-18,00018,00018,19511,88521,523
 
Total water outflows2,771,6713,282,7773,888,2684,454,9882,699,8333,181,054
 
Unaccounted-for difference973,113224,652(299,796)(221,523)(131,938)(34,264)
 
 
Change in water storage      
Change in surface water storage9,475(105,742)(31,775)106,1655,335(56,851)
Change in groundwater storage000000
Total change in water storage9,475(105,742)(31,775)106,1655,335(56,851)
 
Closing water storage343,584334,109439,851471,626365,461360,126
 
 
Change in water assets claims
Urban water supply000000
Urban system entitlement on surface water*000000
Urban system entitlement on groundwater*000000
 
Irrigation scheme(1,736)(3,366)(1,491)(1,934)(33)(8,803)
Irrigation scheme claims on surface water*(1,736)(3,366)(1,491)(1,934)(33)(8,803)
Total change in water assets claims(1,736)(3,366)(1,491)(1,934)(33)(8,803)
 
Change in water liability
Surface water liability(1,706)(3,366)(1,491)(447)(33)(8,803)
Surface water allocation remaining: individual users30001,48700
Surface water liability to urban system supply*000000
Surface water allocation remaining: irrigation scheme*(1,736)(3,366)(1,491)(1,934)(33)(8,803)
 
Groundwater liability(4,800)(6,869)1,830(24)(1)0
Groundwater allocation remaining: individual users(4,800)(6,869)1,830(24)(1)0
Groundwater liability to urban water supply*000000
Total change in water liability(6,506)(10,235)339(471)(34)(8,803)
Net change in water assets14,245(98,873)(33,605)104,7025,336(56,851)

* between-store flows

** data has not provided

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