Adelaide
2.5 Other groundwater assets

Supporting information

The groundwater asset in the Adelaide region includes the managed groundwater volume and the balance of recharged water credits. The opening balance (89,653 ML) and closing balance (90,858 ML) for the groundwater asset in the 2012 Account are grouped by management area and provided in the following table. The groundwater asset could not be separated into water table aquifers and underlying aquifers because allocation and extraction limits are not defined at those levels but rather at the groundwater resource only.

Groundwater asset opening and closing balances for the 2011-12 year
Groundwater management area

Managed groundwater volume1 (ML)

Recharged water credit balance (ML)

Total groundwater asset (ML)

Allocation/ extraction limit

Non-licensed extraction volume (ML)

Volume at 30 June 2011 (ML)

Volume at 30 June 2012 (ML)

Volume at 30 June 2011 (ML)

Volume at 30 June 2012 (ML)

Barossa Prescribed Water Resources Area (PWRA)

7,147

0

0

0

7,147

7,147

McLaren Vale Prescribed Wells Area (PWA)

6,560

500

1

1

7,061

7,061

Northern Adelaide Plains PWA

0

0

3,296

4,501

3,296

4,501

Western Mount Lofty PWRA

70,325

1,824

0

0

72,149

72,149

Total 89,653 90,858

1 The managed groundwater volume is constant across years; therefore the opening and closing balance for the managed groundwater volume does not change.

Managed groundwater volume

The National Water Account recognises the managed groundwater volume as a groundwater asset, provided there is evidence the volume results from an assessment of the resources available to be extracted. In the Adelaide region the managed groundwater volume is the sum of the groundwater extraction limits (or allocation limits) and the non-licensed groundwater extractions described by the relevant water allocation plan. The following prescribed groundwater resources are included in the groundwater asset for the Adelaide region:

The volume reported for the groundwater asset did not include the following prescribed groundwater resources:

  • Northern Adelaide Plains PWA: although the Northern Adelaide Plains has an operational water allocation plan, there is no evidence that this volume is the result of an assessment of the resources available to be extracted .
  • Central Adelaide Plains PWA and Dry Creek PWA do not currently have operational water allocation plans and therefore a managed groundwater volume has not been determined for these resources.

The volume of the Northern and Central Adelaide plains and Dry Creek groundwater asset is considered to be significant compared to the total Adelaide groundwater asset. The Northern Adelaide Plains PWA Water Allocation Planhas identified that the current water allocation on water licenses is 26,500 ML; however the capacity of the resource is insufficient to meet the water use demands (i.e. currently the resource is over-allocated).  Omission of these groundwater resources will have a material impact on the volume reported for the groundwater store and is highly relevant to users of the 2012 Account.

Resource assessments are in progress for the Adelaide Plains Water Allocation Plan that will include Northern Adelaide Plains PWA, Central Adelaide Plains PWA and Dry Creek PWA. Further information on the status of the resource assessment can be found in the South Australian Department of Environment, Water and Natural Resources' Groundwater status reports.

Recharged water credit balance

Recharged water credits accrue from water drained or discharged into a well within the prescribed groundwater resource. The recharged water credit balance is a portion of the recharge credit that may be carried forward (according to the rules detailed in the relevant water allocation plan). For more information about recharged water credits, refer to the Water allocations section of the 'Contextual information'. 

Further information on the groundwater resources for the individual prescribed areas is provided below.

Barossa PWRA

The following table indicates the level of development of the groundwater resource in the Barossa PWRA. The proportion of the total extraction for the Barossa PWRA is shown for each aquifer type.

Groundwater development in the Barossa PWRA

Groundwater management area

Aquifer type

Aquifer

Percentage of extraction

Barossa PWRA

Generally unconfined or semi-confined

Upper aquifer

9%

Confined

Lower aquifer

16%

Confined and unconfined

Fractured rock

55%

Unknown

Unknown

20%


McLaren Vale PWA

The following table indicates the level of development of the groundwater resource in the McLaren Vale PWA. The proportion of the total extraction for the McLaren Vale PWA is shown for each aquifer type.

 

Groundwater development in the McLaren Vale PWA

Groundwater management area

Aquifer type

Aquifer

Percentage of extraction

McLaren Vale PWA

Generally unconfined or semi-confined

Quaternary sediments

<1%

Generally unconfined or semi-confined

Port Willunga Formation

66%

Confined

Maslin Sands

14%

Generally confined

Fractured rock

13%

Not specified

Unknown

8%

Quantification approach

Data source

Water Information and Licensing Management Application (WILMA) database, McLaren Vale PWA Water Allocation Plan (2007), Western Mount Lofty Ranges PWRA draft water allocation plan (2010), Barossa PWRA water allocation plan (2009).

Provided by

South Australian Department of Environment Water and Natural Resources (DEWNR).

Method

Managed groundwater volume

Barossa PWRA

The sum of estimated underground water allocation volumes, detailed in the current Barossa PWRA Water Allocation Plan, is reported as the managed groundwater volume.

McLaren Vale PWA

The estimated sustainable yield and estimated stock and domestic extraction, detailed in the current McLaren Vale PWA Water Allocation Plan, is reported as the managed groundwater volume.

Western Mount Lofty Ranges PWRA

The sum of groundwater extraction limits and existing non-licensed extraction volumes, detailed in the draft water allocation plan for the Western Mount Lofty Ranges PWRA, was reported as the managed groundwater volume. A comprehensive resource assessment provided the value of the groundwater resource capacity. Baseflow and existing non-licensed extractions were deducted from the groundwater resource capacity to quantify the groundwater extraction limit, as shown in the following table.

The sum of groundwater extraction limits, including existing non-licensed extraction volumes, detailed in the draft water allocation plan for the Western Mount Lofty Ranges PWRA, was reported as the managed groundwater volume. The results of a comprehensive resource assessment including groundwater resource capacity, baseflow and extraction limits are summarised in the following table.

Western Mount Lofty Ranges PWRA managed groundwater volume

Catchment

Groundwater resource capacity (ML)

Baseflow (ML)

Existing non-licensed extractions (ML)

Extraction limit (ML)

South Para River

17,004

7,333

156

9,517

Little Para River

5,366

2,163

33

3,171

River Torrens

28,540

11,668

271

16,600

Onkaparinga River

38,932

18,084

413

20,435

Fleurieu Peninsula

52,960

31,407

951

20,602

 Total

142,802

70,655

1,824

70,325


Recharged water credit balance—All management areas in the Adelaide region

The opening and closing recharged water credit balance for the 2011–12 year was extracted from the WILMA licensing database (for more detail see line item 6.1 Groundwater allocation remaining).

Assumptions, limitations, caveats and approximations

Managed groundwater volume

The availability of information to complete a groundwater assessment, the method of assessing the groundwater resource, and the date of the groundwater assessment differs significantly between the management areas. The outcome of the groundwater assessment may produce an extraction limit or an allocation limit. These outcomes are treated in the same manner for the purposes of defining the groundwater asset.   

Recharged water credit balance

The recharged water credit balance is reported as the groundwater asset rather than as the volume injected. The recharged water credit balance is influenced by the conditions for allocating recharge water stated in the relevant water allocation plan. For more information, refer to the Water allocations section of the 'Contextual information'.

Uncertainty information

The uncertainty estimate is not quantified. Completing a volumetric groundwater resource assessment is extremely difficult and relies on incomplete knowledge of the physical processes involved and less than comprehensive monitoring information. Groundwater resource assessments involve making numerous assumptions, some with very high uncertainty.

Comparative year

In the 2012 Account, DEWNR provided corrected values to the Bureau of Meteorology for the recharged water credit balance at 30 June 2011. This correction was a result of DEWNR providing revised estimates for the 2011 Account as better data became available. As a consequence, the volume at 30 June 2011 was restated as per the following table.

 

Restatement of comparative year information for line item 2.5 Other groundwater assets
Groundwater management area

2012 Account volume at 30 June 2011 (ML)

2011 Account volume at 30 June 2011 (ML)

Additional information

Barossa PWRA

7,147

7,147

 
McLaren Vale PWA

7,061

7,070

Volume of recharged water credit at 30 June 2011: changed from 10 ML (2011 Account) to 1 ML (2012 Account) 

Northern Adelaide Plains PWA

3,296

1,886

Volume of recharged water credit at 30 June 2011: changed from 1,886 ML (2011 Account) to 3,296 ML (2012 Account) 

Western Mount Lofty PWRA

72,149

72,149