Adelaide
3.1 Urban water supply system

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

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

SA Water.

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.

• 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).
  

The uncertainty estimate was not quantified.

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

Bureau of Meteorology.

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.

• 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.

The uncertainty estimate was not quantified.

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