Perth
1.1 Storages

This line item refers to the total volume of water within the major surface water storages within the Perth region. These storages are used for urban water supply and irrigation water supply (refer to Table P2 in the Physical information).

Total volume of water within each major storage on 30 June 2010 and 30 June 2011 is given below. The individual storage volumes include the volume of dead storage.

 

Volume of water for each storage within the Perth region at the start and end of the 2010–11 year

Storage	Capacity (ML)	Dead storage (ML)	Storage at 30 June 2011 (ML)	Storage at 30 June 2010 (ML)
Canning	90,300	60	28,183	24,537
Churchman Brook	2,200	40	757	855
Drakes Brook	2,300	20	862	740
Harvey	55,700	780	8,847	21,022
Logue Brook	24,200	380	3,460	10,014
Mundaring	43,000	20,560	22,175	28,853
North Dandalup	73,800	1,020	17,613	25,695
Samson Brook	7,900	90	213	1,362
Serpentine	136,700	1,010	27,860	43,536
Serpentine Pipehead	2,200	460	2,053	2,209
South Dandalup	125,100	12,940	10,025	28,230
Stirling	54,300	1,800	9,961	25,049
Victoria	9,400	50	4,073	2,327
Waroona	14,800	170	1,055	4,038
Wungong	56,400	3,430	23,036	35,411
Total	698,300	42,810	160,173	253,878

The figure below shows that water volume in almost all the storages within the Perth region at the end of the 2010–11 year are less than that at the start (30 June 2010). Except for two storages (Mundaring and Serpentine Pipehead), storage volume within the Perth region was less than 50% of capacity on 30 June 2011.

The large decrease in surface water storage is primarily attributed to the record low inflows into the storages during the 2010–11 year (see Water Corporation website). The record low inflow reflects the well below average rainfall conditions observed throughout the region in the 2010–11 year (see Climate overview).

Graph of water volumes for each storage within the Perth region at the start and end of the 2010–11 year. Capacity of each storage is also shown.

Water Corporation: Operational Data Storage System database.

Water Corporation.

Storage volume at the start and end of the 2010–11 year was calculated using water level data (metres above Australian Height Datum) collected at each storage. Rating tables established for each storage were used to convert the height measurement to a volume.

The volume of individual storages was aggregated to present the total volume for the line item as detailed in the supporting information table.

Storage-volume curves represent specifically surveyed parts of the storage, and may not reflect the storage-volume relationship across the entire storage.

Storages are subject to sedimentation and other physical changes over time, which in turn affects the accuracy of the storage-volume curves.

Derived from measured data. Estimated uncertainty is +/– 5%.

The following table presents substantive changes in the line item reported in this 2011 Account with the corresponding line item in the 2010 Account.

Comparative year information for line item 1.1

2011 Account line item	2010 Account line item	2011 Account volume at 30 June 2010 (ML)	2010 Account volume at 30 June 2010 (ML)	Change from the 2010 Account to the 2011 Account
1.1 Storages	1.1 Storages and reservoirs	253,878	253,878	Change in line item name