- Bioregional Assessment Program
- Gwydir subregion
- 1.1 Context statement for the Gwydir subregion
- 1.1.4 Hydrogeology and groundwater quality
- 184.108.40.206 Groundwater management and use
Groundwater planning and management is undertaken by the NSW Government via water sharing plans. Water sharing plans allow for management of individual groundwater sources and are effective for ten years from their date of commencement. Individual groundwater systems (excluding those of the GAB) are also represented in the Basin Plan 2012 (made under the Water Act 2007) for the MDB as sustainable diversion limit resource units (see Figure 22/Table 10). Relevant water sharing plans within the Gwydir subregion are listed in Table 10, and aligned with corresponding sustainable diversion limit resource units of the Basin Plan. Extraction limits for these groundwater systems are described within:
- individual water sharing plans, as long-term mean annual extraction limits, and
- the Basin Plan, as baseline diversion limits and sustainable diversion limits (Water Act 2007).
Important points regarding water sharing plans and the Basin Plan include:
- With the exception of its topmost confining layers in places (see following dot point), the Surat Basin (a sub-basin of the GAB) is not included in the Basin Plan.
- The GAB Surat Shallow Groundwater Source includes water in the top confining beds of the Surat Basin and overlying alluvial deposits (to 60 m below ground level). It specifically excludes deeper Surat Basin groundwater resources in the productive aquifers.
- The Gunnedah-Oxley Basin MDB sustainable diversion limits resource unit includes the NSW Gunnedah Basin-Bowen Basin system and overlying Oxley sub-basin strata. The ‘Oxley’ component of the basin is not consistently recognised in the literature, but consists of an extension of Pilliga Sandstone in the south-east of the Surat Basin that is hydraulically separated from the rest of the Surat Basin by a groundwater divide. Oxley sub-basin strata are not present in the Gwydir subregion.
- Discrepancy occurs between long-term mean annual extraction limits (LTAAELs) and sustainable diversion limits (SDLs) in the Gunnedah-Oxley Basin and the GAB Surat Shallow Groundwater Source due to differences in the methodologies used to calculate LTAAELs and SDLs. The Basin Plan specifies that the SDL for the Gunnedah-Oxley Basin is to be reviewed before November 2014.
Groundwater extraction and use varies significantly between the groundwater systems in terms of volumes extracted, extraction as a proportion of estimated limits, and actual water use. Current entitlement levels, entitlement limits and recent annual extraction estimates are provided for each groundwater system in Table 11. Only the figures provided for the Lower Gwydir, Border Rivers and Border Rivers Tributary alluvial aquifers are truly representative of the subregion, as the other groundwater systems extend beyond the subregion boundary.
The alluvial aquifers of the Lower Gwydir, NSW Border Rivers and Lower Namoi are the major sources of groundwater supply in the region. Although most of the Lower Namoi Groundwater Source is contained in the Namoi subregion south of the Gwydir subregion, Smithson (2009) indicates that some extraction occurs within the Gwydir subregion, with several individual bores shown to have extracted 501 to 1000 ML/year on average between 2002 and 2007 (this value exceeded 1000 ML/year in one borehole). Most of the groundwater from these systems is used for irrigation. Extraction for town supply and stock and domestic purposes is also significant (Green et al., 2011a). The NSW Government (2010) indicates that there is consultation between NSW and Queensland on the management of the Border Rivers Alluvium.
Groundwater extraction from the GAB is largely for stock and domestic use, and has been historically elevated by uncontrolled flow from bores. This issue has been progressively addressed by programmes such as the Great Artesian Basin Sustainability Initiative (GABSI), which commenced in 1999. As of June 2012, and including bores controlled prior to GABSI, 252 bores in the NSW Surat Basin had been controlled, with estimated water savings of 53,878 ML/year. A further 120 were still to be controlled as at July 2012 (GABCC, 2012). The Eastern Recharge Groundwater Source of the GAB water sharing plan outcrops in the east of the Gwydir subregion where surface water recharges the GAB aquifers. Groundwater is correspondingly of better quality than the deeper water of the Surat Groundwater Source which underlies the west of the subregion, and is consequently suitable for irrigation. High volume extraction for irrigation is reportedly developed at North Star – Croppa Creek in the northern end of the Eastern Recharge Groundwater Source (NSW Government, 2009). Near Moree, confined groundwater from the Pilliga Sandstone supports a local hot spa industry and the Moree town water supply.
Water in the Gunnedah-Oxley Basin is managed under the water sharing plan for the New South Wales Murray–Darling Basin Porous Rock Groundwater Sources 2012. Limited information was found in the literature on water use from the Gunnedah-Oxley Basin, although the water sharing plan indicates considerable access entitlements. While it is noted that the water sharing plan includes three other groundwater sources in addition to the Gunnedah-Oxley Basin, it states that the majority of licences covered by the water sharing plan are for irrigation, with a significant proportion used for industrial purposes. Town access licences total 112 ML/year and estimated stock and domestic rights for the Gunnedah-Oxley Basin are reported in the water sharing plan to be 5779 ML/year. However, the NSW Department of Primary Industries website (NSW Government, 2014) indicates that bores with sufficient yields for irrigation, municipal or industrial use are rare.
Table 10 Groundwater extraction limits comparison – water sharing plans and Murray–Darling Basin Plan
aThese are long-term mean annual net recharge estimates. Annual extraction limits are calculated from these figures by subtracting the volume of planned environmental water – refer to the water sharing plan for the New South Wales Great Artesian Basin Groundwater Sources 2008.
bLTAEL – Long-term average extraction limit
cSDL – Long-term average sustainable diversion limit
dBDL – Baseline diversion limit
eMDB – Murray–Darling Basin
na – Not applicable
Where a separate BDL value is not shown for an SDL resource unit, BDL value = SDL value
Table 11 Groundwater entitlements and extraction
Source: MDBA (2012a), and the Commonwealth’s Basin Plan 2012
BDL – Baseline diversion limit; represents the Murray–Darling Basin Authority’s (MDBA’s) determination of the limits on groundwater use under existing water management arrangements.
SDL – Long-term average sustainable diversion limit; these come into effect in 2019.
NA – Not available
Recent annual extraction includes metered extraction volumes from licensed bores, and estimated extraction from authorised stock and domestic bores reported in MDBA (2012a).
For the NSW Border Rivers Tributary Alluvium there is no metering of licensed groundwater extraction; extraction has been estimated as total entitlements plus estimated extraction from authorised stock and domestic bores.
No information on current entitlements and recent annual extraction are provided for the Great Artesian Basin Surat Shallow Groundwater Source or the Gunnedah-Oxley Basin Murray–Darling Basin Groundwater Source in MDBA (2012a).
The Surat Basin below 60 m (GAB) is not included in the Basin Plan 2012 or MDBA (2012a).
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- 1.1.1 Bioregion
- 1.1.2 Geography
- 1.1.3 Geology
- 1.1.4 Hydrogeology and groundwater quality
- 1.1.5 Surface water hydrology and water quality
- 1.1.6 Surface water – groundwater interactions
- 1.1.7 Ecology
- Contributors to the Technical Programme
- About this technical product