Adelaide
11.2 Non-allocated diversion of surface water

Supporting Information

The volume reported (120,014 ML) was the volume of water harvested from runoff produced within the Adelaide region boundary in the 2010–11 year. The volume reported was the sum of volumes of water diverted from surface water to the urban water system, less the volume of River Murray water discharged to surface water from the urban water system.

Water is imported from the River Murray into the Adelaide region for urban water supply through the Mannum–Adelaide Pipeline, Murray Bridge–Onkaparinga Pipeline and the Swan Reach–Stockwell Pipeline. However, some of the water from these pipelines is released to surface water for transportation to urban water offtakes located further downstream.

For clarity of presentation and to distinguish between water harvested within the region and water imported from outside the region, the discharge to surface water and subsequent diversion from surface water of River Murray water was not reported in the water accounting statements.

The volume of water diverted from Adelaide's surface waters (that was harvested within the region) was calculated by subtracting the volume of water discharged from the River Murray pipes into the surface waters from the overall volume discharged to surface water.

The breakdown of surface water diversions reported here makes the assumption that all water imported from the River Murray is used in the year it is imported and not stored for later years.

Quantification Approach

Overall

Data Source

SA Water: readings may be from either the Supervisory Control and Data Acquisition (SCADA) database or manual field instrument readings, stored in the MetDaily file.

Provided by

Bureau of Meteorology.

Method

The volume of water diverted from Adelaide's surface waters (that was harvested from runoff within the region) was calculated by subtracting the volume of water discharged from the River Murray pipes into surface water (32,025 ML) from the overall volume of water diverted from surface water to the urban water system (152,039 ML).

Assumptions, Limitations, Caveats and Approximations

This calculation method makes the assumption that all water imported from the River Murray is used in the year it is imported and not stored for later years.

Uncertainty Information

The uncertainty estimate was not quantified.

Surface water inflows to the urban water system: metered inflows, metered diversions and mass balance calculations

Data Source

SA Water: readings may be from either the Supervisory Control and Data Acquisition (SCADA) database or manual field instrument readings, stored in the MetDaily file.

Provided by

Bureau of Meteorology.

Method

The volume of surface water diverted to the urban water system was calculated from metered inflows, metered diversions and mass balance calculations as summarised in the following table.

Surface water inflow to the urban water system in the 2010–11 year
Source of diversion Quantification approach Measured/calculated inflow (ML)
Little Para WTP inflow from Little Para River Metered inflow 14,310
Myponga WTP inflow from Myponga River Metered inflow 6,052
Gorge Weir diversion to Hope Valley Reservoir Metered diversion 12,969
Millbrook Reservoir to Millbrook tanks Metered diversion 16,073
Clarendon Weir diversion to Happy Valley Reservoir Metered diversion 92,256
Barossa Weir diversion to Barossa Reservoir Reservoir mass balance 10,379
Total
152,039
WTP = Water treatment plant

Metered diversions

The volumes of water diverted from surface water to urban storages in the 2010–11 year were obtained from SA Water's SCADA database and/or MetDaily file.

Metered inflow

Metered inflow data were obtained from SA Water's SCADA database and/or MetDaily file for the Little Para and Myponga Water Treatment Plants (WTP).

Mass balance
The volume of water diverted from the South Para River to the Barossa Reservoir was calculated using the mass balance calculation described in the following table.

Mass balance calculations used to determine diversion from Barossa Weir to Barossa Reservoir
Function Component Volume (ML)
  Reservoir outflow (Barossa WTP outflow x 1.05) 10,262
add Evaporation 699
less Precipitation 499
less Reservoir initial storage 4,268
add Reservoir end storage 4,185
equals Reservoir inflow (diversion from Barossa Weir) 10,379

Assumptions, Limitations, Caveats and Approximations

The Barossa, Happy Valley, Hope Valley and Onkaparinga Summit reservoirs are considered part of the urban water supply system. This is due to the four storages being located offstream, having minimal runoff and being used solely to service their respective WTPs.

Mass balance
  • no groundwater loss
  • no inflow
  • assumed 5% loss through water treatment process.

Uncertainty Information

Metered inflow
The uncertainty estimate was not quantified.
Mass balance
This calculation was done using broad assumptions. The uncertainty is estimated to be in the range of +/– 12.5%.

Urban water discharge to surface water

Data Source

SA Water: readings may be from either the Supervisory Control and Data Acquisition (SCADA) database or manual field instrument readings, stored in the MetDaily file.

Provided by

Bureau of Meteorology.

Method

The volume of water discharged from the urban water system major pipelines to surface water in the Adelaide region in 2010–11 was determined by obtaining flow gauge measurements from the SA Water's SCADA database and/or MetDaily file.

Water is imported from the River Murray into the Adelaide region for water supply through the Mannum–Adelaide Pipeline, Murray Bridge–Onkaparinga Pipeline and the Swan Reach–Stockwell Pipeline. These pipelines transfer water from the Murray River to the Adelaide region. The water from these pipelines is released to surface water for transportation to urban water offtakes located downstream. The following table shows the locations of these releases and the volumes released in the 2010–2011 year.

Urban water discharge to surface water in the Adelaide region during the 2010–11 year
Source Surface water release point Volume (ML)
Swan Reach–Stockwell Pipeline South Para River 4
Murray Bridge–Onkaparinga Pipeline Onkaparinga River 13,424
Mannum–Adelaide Pipeline River Torrens 5,254
Mannum–Adelaide Pipeline Millbrook Reservoir 1,151
Millbrook tanks Little Para Reservoir 12,192
Total   32,025

Assumptions, Limitations, Caveats and Approximations

  • This item does not include the water imported via the Mannum–Adelaide Pipeline for supply to Barossa Infrastructure Limited (BIL). This volume of water is reported at line item 12.6.
  • For accounting purposes all imported water, and therefore water released to surface water, is assumed to be used in this reporting period.

Uncertainty Information

The uncertainty estimate was not quantified.

Comparative year

This line item corresponds to 19.8.4 Allocation/claim diversion of regulated flows - urban water access entitlement/arrangement reported in the 2010 Account. In the 2011 Account the following changes were made, which caused the values of the 2009–10 year to be restated:

  • Reclassification: in the 2010 Account, a water liability on the surface water store was recognised for surface water diversions to the urban water system. In the 2011 Account, no such water liability was recognised. SA Water's right to abstract surface water for urban water supply is described in the Water rights section of the Contextual information; however there is no entitlement or allocation that creates a water liability for the surface water store within the Adelaide region. This change did not affect the volume reported, but was a material change as it now ensures that the arrangements under which SA Water diverts surface water for urban water supply are accurately reported.
  • Reclassification: in the 2011 Account 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. This change affected some of the locations where surface water diversions to the urban water system were measured, which in turn resulted in a material change to the volume reported at this line item.
  • Change in methodology: in the 2011 Account the volume reported for surface water diversions to urban water system did not include River Murray water imported into the Adelaide region and subsequently discharged to surface water (as described in the Supporting information note), whereas in the 2010 Account it did. This change was made to provide clarity of presentation and to distinguish between water harvested within the region and water imported from outside the region. This change resulted in a material change to the volume reported in the 2010 Account.

These changes are summarised in the following table. The restated comparative year volume is 118,564 ML.


Restatement of comparative year information for line item 11.2 Non-allocated diversion of surface water
2010 Account line item name Source of diversion Volume at 30 June 2010 reported in 2010 Account (ML) Value difference to volume reported due to reclassification (ML) Value difference to volume reported due to change in methodology (ML) Volume at 30 June 2010 reported in 2011 Account (ML)
19.8.4 Allocation/claim diversion of regulated flows - urban water access entitlement/arrangement  Little Para WTP inflow from Little Para River 14,683   (19,320) 118,564
Myponga WTP inflow from Myponga River 5,586  
Happy Valley WTP inflow from Happy Valley Reservoir 66,651 (66,651)
Clarendon Weir diversion to Happy Valley Reservoir   80,297
Anstey Hill WTP inflow from Millbrook tanks 25,118 (25,118)
Millbrook Reservoir to Millbrook tanks   6,377
Hope Valley WTP inflow from Hope Valley Reservoir 19,178 (19,178)
Gorge Weir diversion to Hope Valley Reservoir   18,169
Barossa WTP inflow from Barossa Reservoir 12,899 (12,899)
Barossa Weir diversion to Barossa Reservoir   12,772
Summit Storage WTP inflow from Onkaparinga Summit Reservoir
5,533 (5,533)
Total 149,648 (11,764) (19,320) 118,564