1.1.4.4 Groundwater management and use

Groundwater planning and management is undertaken by the NSW Government via water sharing plans, which provide the means for managing individual groundwater systems and are effective for ten years from their date of commencement. Individual groundwater systems (excluding those of the GAB) are also represented in the Commonwealth’s Water Act 2007 – Basin Plan 2012, for the Murray–Darling Basin. Relevant water sharing plans within the Central West subregion are listed in Table 11, and aligned with corresponding groundwater sustainable diversion limit resource units of the Basin Plan. Extraction limits for these groundwater systems are described within:

Important points regarding water sharing plans and the Basin Plan include:

Discrepancy occurs between long-term mean annual extraction limits (LTAELs) 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 the LTAELs 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 use of the water. Current entitlement levels, entitlement limits and recent annual extraction estimates are provided for each groundwater system in Table 12. Only the figures provided for the Castlereagh, Talbragar and Lower Macquarie alluvial aquifers are truly representative of the subregion, as the other groundwater systems extend beyond the subregion boundary.

The alluvial aquifers of the Upper and Lower Macquarie River are the major sources of groundwater supply in the region. Most of the groundwater from these systems is used for irrigation. Extraction for town supply is also significant, with the city of Dubbo being a major user of groundwater in the Upper Macquarie (Smithson, 2010). Gilgandra also relies on groundwater (Castlereagh Alluvium; Piscopo, 2001).

Groundwater extraction from the GAB is largely for stock and domestic use, and has been historically elevated with a total extraction in the Surat Groundwater Source of about 75,000 ML/y, of which about 90% was lost through leakage and evaporation from bore drains (NSW Government, 2009). This has been progressively addressed by programmes such the Great Artesian Basin Sustainability Initiative, 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). In the Lower Macquarie river basin within the Central West subregion, the sandstone units within the Keelindi and Drildool beds form a locally significant source of water for stock and domestic use, along with groundwater from the overlying alluvial deposits (Macaulay and Kellett, 2009).

Water in the Gunnedah-Oxley Basin sustainable diversion limit resource unit is managed under the water sharing plan for the NSW Murray–Darling Basin Porous Rock Groundwater Sources 2012 (NSW Government, 2013c). Limited information was found in the literature on water use from the Gunnedah-Oxley Basin, although the water sharing plan indicates considerable additional groundwater could be made available for use in the future. The water sharing plan includes three other groundwater sources in addition to the Gunnedah-Oxley Basin, and 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/y and estimated stock and domestic rights for the Gunnedah-Oxley Basin are reported in the water sharing plan to be 5779 ML/y (NSW Government, 2013c).

Table 11 Comparison of water sharing plans and the Murray–Darling Basin Plan

^a These are long-term average net recharge estimates. Annual extraction limits are calculated from these figures by subtracting the volume of planned environmental water – refer to NSW Government (2013a).

^b Long-term average extraction limit (LTAEL)

^cBaseline diversion limit (BDL)/Sustainable diversion limit (SDL). Where only one number is listed, the SDL is equal to the BDL.

Table 12 Groundwater entitlements and extraction

Source data: Commonwealth’s Water Act 2007 – Basin Plan 2012

BDL – Baseline Diversion Limit; represents the MDBA’s determination of the limits on groundwater use under existing water management arrangements.

SDL – Long-Term Average Sustainable Diversion Limits; these come into effect in 2019.

Recent annual extraction includes metered extraction volumes from licensed bores, and estimated extraction from authorised stock and domestic bores.

For the Warrumbungle and Liverpool ranges basalts there is no metering of licensed groundwater extraction; extraction has been estimated as total entitlements plus estimated extraction from authorised stock and domestic bores.

NA signifies that no information on current entitlements and recent annual extraction are provided for the GAB Surat Shallow Groundwater Source or the Gunnedah-Oxley Basin MDB Groundwater Source in MDBA (2012).

na signifies that the Surat Basin below 60 m (Great Artesian Basin) is not included in the Basin Plan (2012) or MDBA (2012).