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Perth: Statement of Changes in Water Assets and Water Liabilities

for the year ended 30 June 2020

  • The volume of water in the region's storages decreased during 2019–20 for the first time in four years.
  • 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 2019–20 was 3,146 GL. Total water outflows was 3,202 GL. Water storage at 30 June 2020 was 55 GL lower 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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 2020 ML2019 ML2018 ML2017 ML2016 ML2015 ML
Water inflows
Surface water inflows 1,171,1121,556,3671,374,9441,782,956778,502937,289
Precipitation41,63756,01455,87737,45316,82421,238
Runoff653,907938,880749,192840,406352,148549,983
Inter-region inflow70,098173,882132,914444,08369,756–
Flood return60871010,67419,919––
Discharge: groundwater*320,720350,701339,369339,166256,534291,896
Discharge: urban supply*81,39533,79784,49699,858**81,104**72,130
Riparian release: urban supply*2,7472,3832,4222,071**2,136**2,042
 
Groundwater inflows 1,385,9741,688,7391,780,1341,637,7151,236,0221,372,693
Inter-region inflow48,03548,56245,77545,72447,47545,218
Inter-region coastal inflow000000
Recharge: landscape1,301,6471,611,1171,701,6021,567,1011,165,1061,304,530
Leakage: urban system*23,55424,13024,27023,43121,87321,155
Managed aquifer recharge*12,7384,9308,4871,4591,568**1,790
 
Urban water system inflows515,221463,014509,463523,067517,538503,927
Wastewater collected135,791141,684141,185140,439138,858140,771
Allocated diversion: surface water*101,929107,81185,63191,326101,204119,649
Allocated extraction: groundwater*135,516122,318131,948139,598136,878122,128
Delivery: desalinated water140,04789,295148,904149,872138,645119,457
Supply system delivery: inter-region1,9381,9061,7951,8321,9531,922
 
Irrigation scheme inflows73,82774,80972,96959,27769,09466,060
Allocated diversion: surface water*73,82774,80972,96959,27769,09466,060
Total water inflows3,146,1343,782,9293,737,5104,003,0152,601,1562,879,969
Water outflows
Surface water outflows1,013,4191,815,0111,618,7821,750,059434,482651,497
Evaporation62,03273,60457,41748,59128,91246,052
Outflow605,7701,287,5801,185,6131,221,652196,413380,925
Leakage: landscape150150150150150150
River losses111,192144,767114,471238,759––
Overbank flow14,52182,69164,36851,454––
Allocation diversion: individual users43,99843,59938,16338,85038,70938,661
Allocated diversion: urban system*101,929107,81185,63191,326101,204119,649
Allocated diversion: irrigation scheme*73,82774,80972,96959,27769,09466,060
 
Groundwater outflows 1,618,6041,676,3601,585,0311,521,1601,361,7811,473,885
Inter-region outflow22,03422,93319,52319,35021,86323,439
Inter-region coastal outflow299,403306,565290,714261,169**233,290**261,245
Discharge: landscape455,872480,437422,166389,247332,617378,114
Discharge: surface water*320,720350,701339,369339,166256,534291,896
Non-allocated extraction: individual users84,03182,88181,79181,25680,84579,610
Allocation extraction: individual users301,028310,525299,520291,374299,754281,453
Allocated extraction: urban system*135,516122,318131,948139,568136,878122,128
 
Urban water system outflows494,144454,577501,755514,501517,992503,488
Supply system delivery: urban users223,123228,344227,634224,799263,200232,537
Recycled water delivery: urban users7,9436,8564,6988,6229,0958,035
Discharge: sea112,235123,224118,202119,190123,163125,025
Discharge: landscape04,6564,4655,7346,1455,962
Supply system transfer: inter-region21,04917,71318,56320,88327,92324,796
Other supply system decreases9,3608,5448,5188,4548,78510,016
Leakage: groundwater*23,55424,13024,27023,43121,87321,155
Supply system discharge: reservoirs*81,39533,79784,49699,858**81,104**72,130
Supply system discharge: riparian release*2,7472,3832,4222,071**2,136**2,042
Managed aquifer recharge*12,7384,9308,4871,4591,568**1,790
 
Irrigation scheme outflows75,75673,95374,29759,37770,65764,528
Delivery54,23352,77754,05943,456**53,456**52,397
Leakage: landscape21,52321,17620,23815,921**17,201**12,131
 
Total water outflows3,201,9234,019,9013,779,8653,845,097**2,384,912**2,657,398
 
Unaccounted-for difference501262,162**135,061**(122,914)**(288,556)**(232,852)
 
 
Change in water storage      
Change in surface water storage(55,288)25,19092,70635,004**(72,312)**(10,281)
Change in groundwater storage––––––
Total change in water storage(55,288)25,19092,70635,004**(72,312)**(10,281)
 
Closing water storage360,128415,416390,226297,520**262,516**334,828
 
 
Change in water claims      
Change in urban system claims000000
Change in irrigation scheme claims*(8,803)2,493(2,940)5,709**(13,770)**7,472
Total change in water claims(8,803)2,493(2,940)5,709**(13,770)**7,472
 
 
Change in water liability
Surface water liability(8,803)2,493(2,940)5,711(13,687)3,322
Allocation remaining: individual users000283(4,150)
Allocation remaining: urban system*000000
Allocation remaining: irrigation scheme*(8,803)2,493(2,940)5,709**(13,770)**7,472
 
Groundwater liability001(4,881)(1,838)(7,337)
Allocation remaining: individual users001(4,881)(1,838)(7,337)
Allocation remaining: urban system*000000
Total change in water liability(8,803)2,493(2,939)830**(15,525)**(4,015)
       
Net change in water assets(55,288)25,19092,70539,883**(70,557)**1,206
 

 

* 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