The volume reported for the opening (93,316 ML) and closing (120,110 ML) balance for storages represents the sum of individual storage volumes (including dead storage) for surface water storages operated by SA Water at 30 June 2010 and 30 June 2011 respectively.
For more information on major surface water storages, refer to the General description section of the Contextual information.
The surface water storage volume, total storage capacity and dead storage are provided in the following table.
|Surface water storages||Total storage capacity (ML)||Dead storage (ML)||Storage volume at 30 June 2010 (ML)||Storage volume at 30 June 2011 (ML)|
|Kangaroo Creek Reservoir||19,000||300||5,814||13,897|
|Little Para Reservoir||20,800||188||3,833||9,416|
|Mount Bold Reservoir||45,900||27||16,703||21,847|
|South Para Reservoir||44,800||310||31,466||38,501|
Surface water storage volume was measured using gauged water level height(s) in metres with respect to the Australian Height Datum for individual storages. The height measurement was converted to a volume using the storage-volume relationship(s) provided by SA Water. The storage volume of individual surface water storages was aggregated to present the total volume for the line item.
Assumptions, Limitations, Caveats and Approximations
Storage-volume relationships were derived from surveys of specific parts of the surface water storage, and may not reflect the storage-volume relationship across the entire storage.
Surface water storages are subject to sedimentation and other physical changes over time, which in turn may affect the accuracy of the storage-volume relationships.
This line item corresponds to line item 1.1 Storages - entitlement system, reported in the 2010 Account. In the 2011 Account, the Bureau of Meteorology (the Bureau) changed the classification of some storages and weirs reported in the 2010 Account in order to provide the users with clearer information. The following changes were made that caused the 2009–10 year value to be restated:
- The Bureau reclassified surface water weirs to line item 1.2 Unregulated river because weirs have a different purpose than the surface water storages. The purpose of weirs is to control river flow to assist with water delivery to the urban water system, whereas surface water storages provide medium to long term water storage for water supply.
- The Bureau reclassified major storages located off-channel as part of line item 3.1 Urban water supply system because they are used for urban water supply only. The criteria for this reclassification required that storages were located off-stream, harvested minimal runoff (due to a diversion channel around the perimeter of the storage) and were used solely to supply their respective water treatment plants.
These changes and their respective volumes are detailed in the table below. The restated comparative year opening balance is 93,138 ML and the closing balance is 93,316 ML.
|2010 Account line item name||Storage||Volume at 30 June 2010 reported in 2010 Account (ML)||Value difference to volume reported due to reclassification (ML)||Volume at 30 June 2010 reported in 2011 Account (ML)
|Opening balance||Closing balance||Opening balance||Closing balance||Opening balance||Closing balance|
|1.1 Storages - entitlement system||Kangaroo Creek Reservoir||4,251||5,814||4,251||5,814|
|Little Para Reservoir||13,174||3,833||13,174||3,833|
|Mount Bold Reservoir||24,378||16,703||24,378||16,703|
|South Para Reservoir||19,459||31,466||19,459||31,466|
|Barossa Weir||91||93||(91)||(93)||Reclassification – now reported at line item 1.2
|Clarendon Weir||268||204||(268)||(204)||Reclassification – now reported at line item 1.2
|Gorge Weir||20||11||(20)||(11)||Reclassification – now reported at line item 1.2
|Gumeracha Weir||199||129||(199)||(129)||Reclassification – now reported at line item 1.2
|Barossa Reservoir||4,232||4,268||(4,232)||(4,268)||Reclassification – now reported at line item 3.1
|Happy Valley Reservoir||9,234||10,100||(9,234)||(10,100)||Reclassification – now reported at line item 3.1
|Hope Valley Reservoir||2,105||2,257||(2,105)||(2,257)||Reclassification – now reported at line item 3.1
|Onkaparinga Summit Reservoir||204||168||(204)||(168)||Reclassification – now reported at line item 3.1|