Melbourne
2.1 Water table aquifer

Supporting Information

The volume presented in the water accounting statements (21,873 ML) represents the sum of the permissible consumptive volume for each water table aquifer groundwater management unit in the Melbourne region.

Permissible consumptive volumes were originally announced in 2006 and represent the maximum annual volume that can be extracted from each groundwater management unit. All previous permissible consumptive volumes were amalgamated into a single order in July 2011.

The following table shows the permissible consumptive volume for each water table aquifer in groundwater management units within the Melbourne region.

Permissible consumptive volumes - water table aquifers

Groundwater Management Unit

Permissible
Consumptive
Volume (ML)

2010–11
allocation (ML)

Licensed
entitlement
(ML)

No. of
Licences

Deutgam Water Supply Protection Area – Groundwater 5,100 3,823 5,097 149
Wandin Yallock Water Supply Protection Area – Groundwater1 2,924 2,933 2,933 187
Frankston Groundwater Management Area 3,200 1,069 1,069 30
Lancefield Groundwater Management Area 1,485 1,390 1,390 15
Merrimu Groundwater Management Area 451 440 440 14
Moorabbin Groundwater Management Area 2,700 2,614 2,614 56
Nepean Groundwater Management Area1 6,013 6,115 6,115 72
Total 21,873 18,384 19,658 523

1 The 2010–11 allocation exceeds the permissible consumptive colume in the Wandin Yallock and Nepean groundwater management units because dairy wash licenses were included in the groundwater licensing framework. Permissible consumptive volumes had not been adjusted at the time of publication to reflect this change.

Kinglake Groundwater Management Area is located on the boundary of the Melbourne region. The majority of the groundwater management unit lies outside of the boundary, and is therefore not considered as part of the total groundwater asset for the Melbourne region. The permissible consumptive volume of Kinglake is 2,015 ML. 

The volume presented does not include groundwater in unincorporated areas outside of groundwater management units. Unincorporated areas have not been evaluated from a groundwater resource perspective and do not have established permissible consumptive volume. The allocation limit for unincorporated areas in the southern half of Victoria was 71,385 ML. The Melbourne region is only a small part of this area.

For a map of groundwater management units in the Melbourne refer to Physical information > Groundwater in the Contextual information .

Quantification Approach

Data Source

Victorian Government Gazette, No. G28, 14 July 2011.

Provided by

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 to set a permissible consumptive volume for each aquifer.

Permissible Consumptive Volumes for the water table aquifers of groundwater management units were determined as follows:

  • Moorabbin groundwater management area, Nepean groundwater management area, Wandin Yallock water supply protection area and Deutgam water supply protection area. Permissible consumptive volumes are based on the total volumes of existing licenses issued for these groundwater management units.
  • Frankston groundwater management area, permissible consumptive volume was determined using rainfall recharge, hydrograph fluctuation, through-flow and aquifer storage.
  • Lancefield groundwater management area, permissible consumptive volume was determined on the rainfall recharge method.
  • Merrimu groundwater management area, permissible consumptive volume was derived from a rounded calculation of rainfall recharge.

Assumptions, Limitations, Caveats and Approximations

  • Permissible consumptive volumes represent the groundwater asset within groundwater management units in the Melbourne region.  An estimate of the size of the groundwater asset in the unincorporated areas outside Groundwater management units has not been made, making it difficult to estimate the total groundwater resource for the Melbourne region.
  • Frankston, Moorabbin, Nepean, Wandin Yallock and Lancefield groundwater management units include all geological formations.
  • Merrimu and Deutgam groundwater management units include all geological formations from 0m to 30m below the surface.

Uncertainty Information

  • Frankston groundwater management area, permissible consumptive volume has a low confidence rating due to uncertainty in the derivation of the infiltration factor, hydrograph and through-flow calculations and the extent of the recharge area.
  • Lancefield groundwater management area, permissible consumptive volume has a low confidence rating due to uncertainty in rainfall infiltration data, recharge processes and distribution.
  • Merrimu groundwater management area, permissible consumptive volume has a low confidence rating due to uncertainty in rainfall infiltration data, recharge processes and distribution.
  • Frankston groundwater management area, and Lancefield GMA permissible consumptive volume estimation assumed rainfall infiltration factors of 5%.
  • Merrimu groundwater management area, permissible consumptive volume assumed rainfall infiltration factors of 10 % in the north, 7.5% in the central area and 5% in the south.

Comparative year

This item corresponds to line item 2.1 Water table aquifer reported in the 2010 Account. There was no change to the volume reported in the 2010 Account. The comparative year volume is 21,873 ML.