Adelaide
3.1 Urban water supply system

Supporting Information

The volume reported for the urban water supply system included water held in urban water storages (including dead storage), pipes and tanks that make up SA Water's potable water supply system.

The Barossa Reservoir, Happy Valley Reservoir, Hope Valley Reservoir and Onkaparinga Summit Reservoir are considered part of the urban water supply system. This is due to the four storages being located off-stream, harvesting minimal runoff (due to a diversion channel around the perimeter of the storage) and being used solely to supply their respective water treatment plants. For more information on the urban water supply system in the Adelaide region, refer to the Other water resources and distribution systems section of the Contextual information.

Major pipelines used to transfer River Murray water into the region were included in the calculation of the pipes volume.

The opening (18,205 ML) and closing (18,218 ML) balances in the 2010–11 year are presented in the following table and itemised by water held in pipes, tanks and urban water storages.


Urban water supply system volumes at the start and end of the 2010–11 year
Urban water supply system Total storage capacity (ML) Dead storage capacity (ML) Storage volume at 30 June 2010 (ML) Storage volume at 30 June 2011 (ML)
Barossa Reservoir 4,510 19 4,268 4,185
Happy Valley Reservoir 12,700 71 10,100 10,399
Hope Valley Reservoir 2,764 123 2,257 2,141
Onkaparinga Summit Reservoir 427 64 168 80
Pipes na na 628 629
Balancing tanks na na 616 616
Process tanks na na 168 168
Total 20,401 277 18,205 18,218

 na – not applicable as storage capacity is assumed to be equivalent to storage volume for urban pipes and tanks

Quantification Approach

Urban water pipes and tanks

Data Source

SA Water: Geographic Information System (GIS) database; storage tank register; and Maximo system.

Provided by

SA Water.

Method

GIS analysis was used to identify potable water tanks and pipes within the Adelaide region. The volume of water in these tanks and pipes was estimated from their total capacity.

The volumes of water held in tanks were collected from SA Water's storage tank register and Maximo system.

The volumes of water held in pipes were estimated from pipe lengths and nominal diameters (stored in the Maximo system) using the following formula:

π  x (D/2) x (D/2) x PL

D = Nominal diameter of the pipe

PL = Pipe length.

Some tanks did not have volumes recorded in the database (< 5%). Queries with key staff obtained these volumes.

Assumptions, Limitations, Caveats and Approximations

  • Process tanks and pipes were assumed to be 100% full in winter, while balancing tanks were assumed to be 50% full.
  • Pipes without recorded construction dates were assumed to have been constructed before the 2010–11 year. It is assumed that all tanks were constructed before the 2010–11 year.
  • Only tank and pipe assets that are owned by SA Water were included in the calculation.
  • Nominal diameters of pipes were used to calculate volumes.
  • Fire service mains pipe assets were not included, however the volume was negligible (<1 ML).

Uncertainty Information

The uncertainty estimate was not quantified.

Urban water storages

Data Source

Bureau of Meteorology: Australian Water Resources Information System water storages.

Provided by

Bureau of Meteorology.

Method

Storage volume was measured using gauged water level height(s) in meters 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 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 water storage, and may not reflect the storage-volume relationship across the entire storage. 

  • Water storages are subject to sedimentation and other physical changes over time, which in turn may affect the accuracy of the storage-volume relationships.

Uncertainty Information

The uncertainty estimate was not quantified.

Comparative year

This line item corresponds to line item 5.1 Urban potable water supply reported in the 2010 Account. The following changes were made that caused the 2009–10 year value to be restated:

  • The Bureau of Meteorology reclassified major storages located off-channel as part of line item 3.1 Urban water supply system to provide clearer information to users. 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 soley to supply their respective water treatment plants.
  • An error in the volume reported for potable water pipes was identified due to data quality improvement processes. Although the change to the volume reported was small, the volume was restated to correct this error and provide comparability between years.

These changes and their respective volumes are detailed in the following table. The restated comparative year opening balance is 17,187 ML and the closing balance was 18,205 ML.

Restatement of comparative year information for line item 3.1 Urban water supply system
2010 Account line item name Urban water supply system Volume at 30 June 2010 reported in 2010 Account (ML) Value difference to volume reported due to prior period error correction (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 Opening balance Closing balance
5.1 Urban potable water supply system Barossa Reservoir         4,232 4,268 4,232 4,268
Happy Valley Reservoir         9,234 10,100 9,234 10,100
Hope Valley Reservoir         2,105 2,257 2,105 2,257
Onkaparinga Summit Reservoir         204 168 204 168
Potable water pipes 610 610 18 18     628 628
Balancing tanks 616 616         616 616
Process tanks 168 168         168 168
Total

1,394 1,394 18
18
15,775 16,793 17,187 18,205