Melbourne

Within the Statement of Changes in Water Assets and Water Liabilities, the volume recognised (0 ML) represents the fact that no contracted volume of water was delivered into the region during 2009-10.
 
Within the Statement of Physical Water Flows, the volume recognised in the water accounting statements (84,443 ML) represents the total volume of water that was actually transferred-in to the Melbourne region during 2009–10.

Connected surface water – interbasin claims 2009–10

	Statement*	Account	Volume (ML)
	SWAWL	Opening balance (01 July 2009); 7.1 Interbasin claim on water – remaining	157,200
add	SCWAWL	23.4 Other lumped non-physical surface water asset increase	151,809
less	SCWAWL	13.6.3 Delivery of water transferred-in under interbasin agreement to connected surface water	0
less	SPWL	13.6.3 Delivery of water transferred-in under interbasin agreement to connected surface water	84,443**
	SWAWL	Closing balance (30 June 2010); 7.1 Interbasin claim on water – remaining	224,566

* SWAWL: Statement of Water Assets and Water Liabilities
SCWAWL: Statement of Changes in Water Assets and Water Liabilities
SPWL: Statement of Physical Water Flows

**Volume breakdown given below

 

Water transferred-in to the Melbourne region during 2009–10

Transfer-in to region	Volume (ML)
Transfers of water from Thomson Reservoir	62,400
Transfers of water from Lake Eildon via the North–South Pipeline	16,743
Transfers of water from the Goulburn River catchment (Silver and Wallaby creeks)	5,300
Total	84,443

Data source

Melbourne Water: Waterworks database.

Data provider

Melbourne Water.

Method

The total volume of water transferred-into the Melbourne region under an inter-basin agreement is the sum of the following components:

• Transfers of water from the Thomson Reservoir
  The volume of water transferred-in from the Thomson Reservoir was measured by the depth of water flowing over the spillway chute at the inflow point to Upper Yarra Reservoir (which behaves as an Ogee weir) using a Mindata 2100P level sensor. The water depth was converted to flow using a stage-discharge relationship.
  
  
• Transfers of water from Lake Eildon via the North–South Pipeline
  The volume of water transferred-in from Lake Eildon was measured at the Sugarloaf Pipeline Pump Station. There are six pumps at the pump station, which are divided evenly into two pump-well groups. The total volume of water diverted from the Goulburn River was calculated as the sum of the volume pumped from the two wells, measured using a Siemens Sitrans SONOKIT dual-beam ultrasonic flow meter.
  
  
• Transfers of water from the Goulburn River catchment (Silver and Wallaby creeks)
  The volume of water transferred-in from the Silver and Wallaby creek catchments to the Toorourrong and Yan Yean reservoirs occurs via Clearwater Channel. Clearwater Channel also diverts water from the Plenty River (in the Melbourne region) to Yan Yean Reservoir. The total volume of water transferred along the Clearwater Channel was metered after the point where water enters from Plenty River.
  

Based on historical records of catchment runoff, the flow along Clearwater Channel was estimated to comprise 64% of the water transferred-in from the Silver and Wallaby catchments, and 36% of water diverted from the Plenty River.
The volume of water transferred-in from the Silver and Wallaby catchments was derived by multiplying the Clearwater Channel meter reading by a factor of 0.64.

Uncertainty

The uncertainty relates to the accuracy of the measurement device used to measure the volume of water transferred-in. The uncertainty for each transfer is shown below:

• transfer of water from the Thomson Reservoir: estimated uncertainty is +/–2%
• transfer of water from Lake Eildon via the North–South Pipeline: estimated uncertainty is +/–1%
• transfer of water from the Goulburn River catchment (Silver and Wallaby creeks): estimated uncertainty is +/–1%.

Approximations, assumptions, caveats/limitations

The factor applied to derive the flow from water transferred-in from the Silver and Wallaby catchments is based on historical data.