Melbourne

                                                                                                   

2.2 Underlying aquifers

                             

Supporting information   


The volume recognised in the water accounting statements (16,565 ML) represents the sum of the Permissible Consumptive Volume for each Groundwater Management Unit in the Melbourne region. Permissible Consumptive Volumes were announced in 2006, and represent the maximum annual volume that can be extracted from each Groundwater Management Unit.

The volume does not include unincorporated areas outside the Groundwater Management Unit areas. Unincorporated areas have not been evaluated from a groundwater resource perspective, and do not have established Permissible Consumptive Volumes.

The table below shows the Permissible Consumptive Volume for each underlying aquifer Groundwater Management Unit within the Melbourne region.

 

Permissible consumptive volume for each underlying aquifer groundwater management unit in the Melbourne region
Groundwater management unit Formation Volume (ML)
Koo Wee Rup Water Supply Protection Area – Groundwater All formations

12,915
Cut Paw Paw Groundwater Management Area All formations >50 m

3,650
Total

16,565

 

Quantification approach   


Data source

Victorian Government Gazette, no. G 44, 02 November 2006.

Data provider

Victorian Department of Sustainability and Environment.

Method

The Victorian Department of Sustainability and Environment determined the volume of underlying aquifers in Groundwater Management Unit areas in order to set a Permissible Consumptive Volume for each aquifer.

Permissible Consumptive Volumes for the Groundwater Management Unit areas were modelled as follows:

  • Koo Wee Rup Water Supply Protection Area Permissible Consumptive Volume is based on numerical modelling and observed response to pumping.
  • Cut Paw Paw Groundwater Management Area Permissible Consumptive Volume was based on the through-flow method.

Uncertainty

Uncertainty is ungraded.

  • Permissible Consumptive Volumes are prescribed and consequently have no uncertainty. However, Permissible Consumptive Volumes are constructs based in part on modelling and historical extraction.
  • Permissible Consumptive Volumes apply only to the Groundwater Management Unit areas of Melbourne region. Estimating the size of the groundwater asset based on Permissible Consumptive Volumes means that no estimate is made of the size of the groundwater asset for land outside of Groundwater Management Unit areas.
  • Estimating the size of the groundwater asset as at 30 June 2010 by summing Permissible Consumptive Volumes, therefore, is highly uncertain.

Approximations, assumptions, caveats/limitations

  • Groundwater Management Units where the bulk of extraction is from depths greater than 50 m are considered underlying aquifers.
  • Cut Paw Paw Groundwater Management Area Permissible Consumptive Volume has a low confidence rating due to uncertainty in aquifer parameters and potentiometry.
  • Cut Paw Paw Groundwater Management Area Permissible Consumptive Volume was based on the assumption that through-flow is equal to the safe groundwater extraction volume.