The Perth region
Overview of the 2011–12 year
Rainfall across the entire Perth region was generally close to average for the 2011–12 year. These rainfall conditions, compared to the record low rainfall observed during the 2010–11 year, contributed to increased inflows into the storages. The volume of water held in storages increased during the 2011–12 year by 49,282 ML: a substantial change from the previous year, where water storage decreased by 93,705 ML. Closing net water assets in the Perth region was 52,048 ML, compared to –20,630 ML at the end of the 2010–11 year. For more information on the region's water assets refer to Water accounting statements.
During the 2011–12 year the second desalination plant commenced operation within the Perth region. This increased the supply of desalinated water to the urban water system by more than 50% from the previous year. Desalinated water made up 25% of the urban supply water during the 2011–12 year. Consequently, there was a decreased dependence of surface water and groundwater for urban supply compared to the previous year.
The key water account information for the Perth region during the 2011–12 year are presented in the following table. Information on the uncertainty associated with the volumes presented in the table is provided in the relevant sections of the account.
Key water account information for the Perth region during the 2011–12 year
 |
2011–12 | 2010–11 | Long–term average (1900–2011) |
| Rainfall: 805 mm | Rainfall: 502 mm | Rainfall: 781 mm | |
| Evapotranspiration: 689 mm | Evapotranspiration: 399 mm | Evapotranspiration: 666 mm | |
| For more detail on the Perth climate refer to Climate overview. | |||
 |
Swan-Canning River | Murray River | Harvey River |
| Below mean annual flow | Below mean annual flow | Below mean annual flow | |
| For more detail on streamflow in the Perth region refer to Water overview. | |||
 |
2011–12 | 2010–11 | |
| Total water assets (as at 30 June) | 217,185 | 167,546 | |
| Total water liabilities (as at 30 June) | 165,137 | 188,176 | |
| Change in net water assets | 72,678 | (89,907) | |
| Closing net water assets | 52,048 | (20,630) | |
| For more detail on water assets and water liabilities refer to Water accounting statements. | |||
Notes: Water resources and systems
 |
30 June 2012 | 30 June 2011 | |||
| Total capacity | Volume | % of capacity | Volume | % of capacity | |
| 698,300 ML | 209,455 ML | 30.0% | 160,173 ML | 22.9% | |
| For more detail on surface water storage in the Perth region refer to Surface water. | |||||
 |
Total water abstracted | ||
| 2011–12 | 2010–11 | Recent activity | |
| Surface water: 155,347 ML | Surface water: 217,072 ML | Water abstraction for urban water supply has decreased | |
| Groundwater: 512,137 ML | Groundwater: 519,660 ML | ||
| For more detail on water abstraction in the Perth region refer to Surface water and Groundwater. | |||
 |
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| Total water supplied | |||
| 2011–12 | 2010–11 | Recent activity | |
| 318,189 ML | 332,908 ML | Increased dependence on desalinated water supply | |
| For more detail on the urban water system in the Perth region refer to Urban water system. | |||
 |
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| Total water supplied | |||
| 2011–12 | 2010–11 | Recent activity | |
| 24,133 ML | 32,952 ML | Diversion of surface water to the scheme has decreased | |
| For more detail on the irrigation scheme in the Perth region refer to Irrigation scheme. | |||