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Perth: Statement of Changes in Water Assets and Water Liabilities

For the water account period 1 July 2023 to 30 June 2024

  • The volume of water in Perth's storages decreased by 106 GL during 2023–24.
  • 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 2023-24 was 2,954 GL. Total water outflows was 3,285 GL. Water storage on 30 June 2024 was 106 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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 2024 (ML)2023 (ML)2022 (ML)2021 (ML)2020 (ML)2019 (ML)
Water inflows
Surface water inflows 1,119,3461,931,6312,600,9181,182,5861,143,8991,797,814
Precipitation on storages25,52939,09141,99734,50629,95335,451
Precipitation on rivers15,88026,80234,99520,27516,67426,134
Discharge from groundwater*259,450302,709276,504197,429320,720350,701
Flood return1,4482,17411,8793116142,441
Inflow from outside region74,724367,067529,79081,43969,936173,882
Runoff656,8471,137,9881,641,634767,425621,4911,175,408
Urban water return*85,46855,80064,11981,20184,51133,797
 
Groundwater inflows 1,211,0531,659,9611,602,7351,085,0861,425,4891,731,918
Inter-region coastal inflow45,55935,04737,91535,68839,51543,179
Inter-region inflow44,58543,96443,15343,06048,03548,562
Recharge from landscape1,078,2941,541,5361,479,365970,7251,301,6471,611,117
Leakage from urban water system*26,11625,06327,27820,32323,55424,130
Managed aquifer recharge from urban system*16,49914,35115,02415,29012,7384,930
 
Urban water system inflows556,194498,654512,911519,733515,221463,015
Delivery of desalinated water119,54794,474116,198143,641140,04789,295
Diversion of surface water*136,511120,264121,32698,358101,929107,811
Extraction of groundwater*149,929136,790130,256137,064135,516122,318
Inter-region delivery to the urban system2,2611,9801,9962,0061,9381,906
Wastewater collected147,946145,146143,135138,664135,791141,685
 
Irrigation scheme inflows67,86665,99166,11249,70173,82774,809
Allocated diversion from irrigation scheme*67,86665,99166,11249,70173,82774,809
 
Total water inflows2,954,4594,156,2374,782,6762,837,1063,158,4364,067,556
Water outflows
Surface water outflows1,017,7321,798,0212,382,438898,227929,8961,672,595
Evaporation from storages58,13358,45859,70051,09755,71761,015
Evaporation from rivers17,91420,67222,82818,37317,57920,204
Leakage to landscape150150150150150150
Outflow to sea658,0851,395,9411,932,079622,272617,5961,280,713
Overbank flow28,67792,220136,15013,10319,10084,294
River losses------
Allocated diversion to individual users50,39644,32544,09345,17343,99843,599
Allocated diversion to irrigation scheme*67,86665,99166,11249,70173,82774,809
Diversion to the urban system*136,511120,264121,32698,358101,929107,811
 
Groundwater outflows 1,622,5921,527,1191,489,1381,228,5111,658,1211,721,820
Discharge to landscape447,826354,339354,819232,977455,872480,437
Discharge to surface water*259,450302,709276,504197,429320,720350,701
Inter-region coastal outflows305,992324,966319,566257,986338,920351,830
Inter-region outflows18,88819,47319,19618,07022,03423,128
Allocation extraction to individual users332,000302,700304,017300,495301,028310,525
Extraction to the urban system*149,929136,790130,256137,064135,516122,318
Non-allocated extraction to individual users108,50786,14284,78084,49084,03182,881
 
Urban water system outflows566,979493,844517,270524,368512,353452,194
Discharge to sea127,660122,846124,616119,613112,235123,224
Leakage to groundwater*26,11625,06327,27820,32323,55424,130
Managed aquifer recharge*16,49914,35115,02415,29012,7384,930
Other losses9,5128,5528,5478,4308,3858,544
Return to surface water*85,46855,80064,11981,20184,51133,797
Supply of drinking water for own use1,6581,0509858929750
Supply of drinking water to agriculture and irrigation customers798013012193101
Supply of drinking water to commercial and industrial customers29,56326,60526,39725,86225,70927,849
Supply of drinking water to other customers18,70616,61117,12816,36018,11418,259
Supply of drinking water to other regions37,50534,25740,17844,46137,60217,713
Supply of drinking water to residential customers206,992185,027184,673182,236180,494182,135
Supply of recycled water for own use2,4172,5382,7893,3672,5452,245
Supply of recycled water to agriculture and irrigation customers0000320
Supply of recycled water to commercial and industrial customers3,75304,3615,1325,3664,611
Urban discharge to landscape1,0511,0641,0451,08004,656
 
Irrigation scheme outflows77,48466,30066,14248,71775,75673,953
Irrigation delivery59,48448,30047,94736,83254,23352,777
Leakage to landscape from irrigation18,00018,00018,19511,88521,52321,176
 
Total water outflows3,284,7873,885,2844,454,9882,699,8233,176,1263,920,562
 
Unaccounted-for difference224,585(302,727)(221,523)(131,948)(39,161)(121,323)
 
 
Change in water storage      
Change in surface water storage(105,743)(31,774)106,1655,335(56,851)25,671
Change in groundwater storage------
Total change in water storage(105,743)(31,774)106,1655,335(56,851)25,671
 
Closing water storage334,109439,852471,626365,461360,126416,977
 
 
Change in non-physical irrigation water assets      
Claims: surface water*(3,366)(1,491)(1,934)(33)(8,803)2,493
Total change in water claims(3,366)(1,491)(1,934)(33)(8,803)2,493
 
 
Change in water liability
Surface water liability(3,366)(1,491)(447)(33)(8,803)2,493
Allocation remaining: individual users001,487000
Allocation remaining: irrigation scheme*(3,366)(1,491)(1,934)(33)(8,803)2,493
 
Groundwater liability(6,869)1,830(24)(1)00
Allocation remaining: individual users(6,869)1,830(24)(1)00
Total change in water liability(10,235)339(471)(34)(8,803)2,493
       
Net change in water assets(98,874)(33,604)104,7025,336(56,851)25,671

* between-store flows

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