Melbourne
18.11 Entitled extraction of allocated groundwater to users

Supporting information

The volume presented in the water accounting statements (15,412 ML) represents metered extraction and estimated stock and domestic extraction under groundwater entitlements in groundwater management units in the Melbourne region.

The following table shows the breakdown of groundwater volumes extracted from groundwater management units in the Melbourne region during the 2012–13 year. The allocation announcement for the 2012–13 year are given in line item 22.1 Groundwater Allocation announcements.

Groundwater allocation extraction in the Melbourne region during the 2012–13 year
Groundwater management unit Metered extraction (ML) Estimated Stock and Domestic extraction (ML) Usage of allocation %
Cut Paw Paw groundwater management area (GMA)
208 41 44%
Deutgam water supply protection area (WSPA)—groundwater 1,389 217 30%
Frankston GMA 218
180 21%
Koo Wee Rup WSPA—groundwater 3,474 1,988 36%
Lancefield GMA
94 96
16%
Merrimu GMA 28 18 10%
Moorabbin GMA 1,053 465 47%
Nepean GMA 3,159 2,147 51%
Wandin Yallock WSPA—groundwater 450 187 20%
Subtotal 10,073 5,339 37%
Total extraction   15,412  


Quantification approach

Data source

Victorian Water Register.

Provided by

Victorian Department of Environment and Primary Industries.

Method

The volume presented for this item is a combination of metered extraction data and estimates of non-metered extractions.

Metered extractions

Southern Rural Water meter groundwater extractions and submit this data to the Victorian Water Register. Metered extraction volumes were obtained from the Victorian Water Register for all groundwater management units for the 2012–13 year.

Unmetered estimated extractions

Stock and domestic entitlements are not currently metered in Victoria. Extraction was estimated by multiplying a usage factor between 0 and 2 ML by the number of stock and domestic bores in the region:

  • a factor of zero estimates that no extraction occurred; and
  • a factor of two estimates that the full entitlement was extracted.

During the 2012–13 year, a usage factor of 1.5 was applied to all stock and domestic entitlements, with the exception of Nepean GMA where a usage factor of 1 was applied.

Assumptions, limitations, caveats and approximations

  • Not all groundwater bores are metered. Bores that were not metered were not used or did not fall within the threshold of Southern Rural Water's metering program. The number of non-metered bores is estimated to be 10-20% of the total bores in the area. The volume of extraction from bores that are not metered is not considered to have a material impact on this water accounting report.
  • A broad assumption is made to estimate stock and domestic extraction. It is unlikely that all extraction matches the assumption. In a wet year, the estimate is likely to overestimate the volume of stock and domestic extraction.

Uncertainty information

  • Metered data has an uncertainty of +/–5% based on meter specifications.
  • Estimated data has an uncertainty of +/–100% based on the broad assumptions applied.