A water account provides a summary of resource availability for a defined area through quantifying storage volumes, inflows and outflows within a management framework. For groundwater, aquifer storage capacity and actual storage volumes are often not known or difficult to quantify, so extraction limits or entitlements on issue for a groundwater source can be used as a surrogate for the water available for use. Inflows in a groundwater context refer to aquifer recharge. Outflows refer to natural discharges (e.g. to rivers and springs) and extractions for human use. The groundwater accounts presented here use: extraction limits, if prescribed, or entitlements on issue to define the water available for use; recharge estimates from NSW Department of Water and Energy (2009) for inflows, where available; and estimates of extraction for human use for outflows, where available. Natural discharges (e.g. via baseflow, springs) are not reported because measured data are not generally available. Estimates of baseflow from the literature and based on digital filtering baseflow separation are reported in sections 1.1.5 and 1.1.6 of companion product 1.1 Context statement for the Hunter subregion (McVicar et al., 2015) and Section 2.3.2 from companion product 2.3 for the Hunter subregion (Dawes et al., 2016), which range from 20 to 63% of streamflow.
Water licence datasets, including licence type, entitlement volume (if applicable) and location of the bore (if recorded), for the Hunter subregion were obtained from NSW Office of Water (Dataset 1) and used in the compilation of the asset database for the Hunter subregion (Bioregional Assessment Programme, Dataset 2). NSW requires that all bores have a work approval and are registered, regardless of the intended purpose. Under NSW’s Water Management Act 2000 (the Water Management Act), a water access licence is required to extract water for all consumptive purposes except basic landholder rights (for example, for stock and domestic purposes).
A water access licence entitles the licence holder to:
- specified shares in the available water within a particular water management area
- take water at specified times, rates or circumstances from specified areas or locations.
Following the introduction of a water extraction monitoring policy in 2009 (NSW Department of Water and Energy, 2009; see Section 1.5.1.1.6), bores licensed for extraction for commercial purposes within a water allocation scheme under NSW’s Water Act 1912 (the Water Act) must have a meter and an annual extraction limit. Under the Water Management Act, requirements for metering are specified through water sharing plans (WSPs). Older plans, such as the Water Sharing Plan for the Kulnura Mangrove Mountain Groundwater Sources 2003, make no provisions for metering of groundwater extractions. Newer plans can at the direction of the Minister require metering equipment to be installed or for the licensee to maintain a logbook of extractions. The Draft Water Sharing Plan for the North Coast Fractured and Porous Rock Groundwater Sources 2015 is an example of this. In the Hunter subregion in 2015, metering of groundwater extractions was minimal and it is difficult to quantify actual groundwater extraction volumes. However, as new water allocation schemes and groundwater sharing plans are rolled out, it is expected that metered extraction data will become more readily available and better estimates of groundwater extraction volumes will be possible.
Groundwater availability
Aquifers in the Hunter subregion can be broadly classed into three hydrogeological types: alluvial, coastal sands, and fractured (including porous) rock aquifers. The alluvial and coastal sands aquifers are relatively localised hydrostratigraphic units, occurring along the main river valleys and close to the coastline. The alluvial deposits tend not to be deeper than about 20 m, while the coastal sands aquifers average about 20 m, but can be up to 50 m deep. The deeper, more extensive aquifer systems occur within fractured and porous rock across the subregion. Figure 9 shows the distribution of groundwater bores across the Hunter subregion classified according to the aquifer type from which each bore accesses water. Not all bore data include screening depth or stratigraphy that enable them to be mapped to their water source, so they have been classified based on the following assumptions: (i) any bore overlying mapped alluvium and shallower than 20 m is an alluvial bore; (ii) a bore overlying a coastal sands aquifer is a coastal sands bore; and (iii) all other bores are in fractured or porous rock aquifers (classed here as fractured rock aquifers). The assumptions may not hold in all cases, so the classification is indicative, rather than definitive. It can be seen that alluvial bores are concentrated along the Hunter River valley around Maitland, Singleton, between Muswellbrook and Scone and between Muswellbrook and the junction with the Goulburn River, with smaller concentrations around Bylong and the lower Goulburn River. There is a high density of bores north of Newcastle that tap water stored within the Tomago Tomaree Stockton Sandbeds, an important coastal aquifer for Newcastle water supply. The distribution of deeper bores is more widespread, except within the conservation areas to the south of the subregion.
Figure 9 Hunter subregion bores classified by hydrogeological aquifer type
Data: Bioregional Assessment Programme (Dataset 2)
It is difficult to quantify the volumes of water physically stored within the different aquifers. Instead the definition of groundwater availability adopted here is based on the volumes defined as available for consumptive use within NSW’s groundwater management framework.
Water sharing plans, established under the Water Management Act, define rules for sharing water between the environmental needs of the aquifer and water users, and also between different types of water use such as town supply, rural domestic supply, stock watering, industry and irrigation (NSW Department of Primary Industries, 2015). While not all groundwater sources in the Hunter subregion are currently covered by WSPs, progress is being made towards achieving complete coverage. As at September 2015, there were four groundwater-specific WSPs in place that intersect all or part of the Hunter subregion; there are another two WSPs that deal with the management of surface water and groundwater within the alluvial aquifers to which they apply, but exclude fractured rock aquifers; and there is a fifth groundwater-specific WSP, which is at a draft stage (on public exhibition from 8 February 2016), that will intersect the Hunter subregion (Table 10). Figure 10 shows the extent of the six plans that have commenced. The overlap of the Hunter subregion with the NSW Murray Darling Basin fractured and porous rock WSP area is relatively small and licensed entitlement volumes for these resources are not reported here.
Table 10 Water sharing plans that apply to groundwater resources in the Hunter subregion
Source: DPI Water (2015a)
Most of the alluvial groundwater in the Hunter subregion is managed under the Hunter Unregulated and Alluvial Water Sources WSP (NSW Government, 2009). The alluvial aquifers are considered to be highly connected to surface water, and are generally managed conjunctively with the surface water source they are associated with. Alluvial groundwater availability, defined in terms of licensed entitlements to extract water, is defined for each unregulated water source area and for the Hunter Regulated River water source (Figure 10) and summarised in Table 11 for those water source areas that intersect the subregion. The licensed entitlement volume from all these water sources is estimated to be 93.3 GL/year as at 24 March 2015. Some of these water source areas extend outside the subregion and the values provided in Table 11 reflect the entire water source. For example, there are no groundwater licence holders in that part of the Williams River water source that intersects the subregion; and in the Pages River water source, the 4 licence holders within the subregion are entitled to 0.12 GL/year, with the remaining 7.28 GL/year of entitlement licensed to users outside the subregion. The surface water entitlements for these water sources are summarised in Table 8.
On 5 February 2016, DPI Water placed an embargo (with exemptions) on further applications for commercial water licences for groundwater within the Hunter water shortage zone (refer to Map 1 in DPI Water (2016)), an area which covers almost the entire Hunter subregion. The embargo reflects an assessment that the groundwater sources within this zone are unlikely to have sufficient water to meet the requirements of licensees within this zone. The embargo does not apply to groundwater within the WSP areas of the Hunter Unregulated River and Alluvial water sources, Hunter Regulated River water source, Kulnura Mangrove Mountain groundwater sources or the Tomago Tomaree Stockton groundwater sources.
Figure 10 Water sharing plans for managing groundwater resources in the Hunter subregion
Data: NSW Office of Water (Dataset 3, Dataset 4)
Table 11 Groundwater entitlements at 24 March 2015 and estimated rainfall recharge by water source
Listed in descending order of total licensed entitlements. The boundaries of the areas covered by these water sharing plans extend beyond the Hunter subregion.
aOnly a portion of the water source falls within the Hunter subregion.
bThis water source was set to be merged in 2015 with the water sharing plan for the Hunter Unregulated and Alluvial water sources.
cIncludes only licences in the subregion (current February 2016)
dNSW Department of Water and Energy (2009)
NA = data not available
Data: NSW Office of Water (Dataset 1)
The accessible aquifer volume for the Tomago Sandbeds is 60 GL from a maximum storage volume of about 100 GL (Hunter Water Corporation, 2011). Under the WSP for the Tomago Tomaree Stockton Groundwater Sources 2003, long-term average annual extraction limits (LTAAEL) have been set at 25 GL/year for Tomago, 6 GL/year for Tomaree and 14 GL/year for Stockton sandbeds (NSW Government, 2003).
The WSP for the Kulnura Mangrove Mountain Groundwater Sources provides LTAAEL for eight water sources within the plan area. In total, this has been set at 6.29 GL/year (NSW Department of Primary Industries, 2013).
Based on the aforementioned licensed entitlement volumes and LTAAEL for the main groundwater source areas in the Hunter subregion, the groundwater available for extraction is about 145 GL/year, with an unspecified volume permitted from fractured and porous rock aquifers under basic water rights.
To obtain an estimate of the total volume of water licensed to be extracted from groundwater within the Hunter subregion, the water entitlement volumes for every bore in the Hunter assets database (Bioregional Assessment Programme, Dataset 2) were summed. A total of 128.46 GL of groundwater is potentially available for extraction each year. This estimate includes bores in porous and fractured rock aquifers not covered by current WSPs, so cannot be directly related to the licensed entitlement volumes by water source area in Table 11 and preceding paragraphs. Again, this total does not include basic water rights for domestic and stock use (around 2389 bores in Bioregional Assessment Programme, Dataset 2), for which the volume of take is not specified but generally assumed to be 2 ML/year per bore (Realica-Turner, In prep.), translating to not more than about 4.8 GL/year across all domestic and stock bores.
Recharge
Recharge is the addition of water to a groundwater system. It usually comes from rainfall and surface water bodies, such as rivers and lakes, but can also come from adjacent groundwater systems. Long-term mean annual rainfall recharge is often used as the basis for defining LTAAEL for groundwater sources and is an important term of a groundwater account. Rainfall recharge rates are reported in report cards (NSW Department of Water and Energy, 2009) for some of the water source areas covered by the Hunter Unregulated and Alluvial Water Sources WSP, and have been provided in Table 11 . However, in a recently released report on macro WSPs to assist community consultations (DPI Water, 2015b), DPI Water provides recharge estimation principles, as a basis for water sharing in groundwater sources in NSW that take account of factors other than just rainfall recharge. In coastal NSW, the long-term mean annual rainfall recharge remains the basis for water sharing in fractured rock, porous rock and coastal sands aquifers. The broad approach to calculating mean annual recharge is to multiply mean annual rainfall by an infiltration factor. For coastal sands, the infiltration factor is 30%, coastal alluvials 10%, coastal porous rock up to 6% and fractured rock 4%, although these can be varied based on more local information.
Rainfall recharge is not the basis for water sharing in coastal upland alluvial aquifers, such as those covered by the Hunter Unregulated and Alluvial Water Sources WSP. These alluvial aquifers are managed conjunctively with the surface water system and the LTAAEL is based on current entitlements.
Estimates of recharge across the Hunter subregion have been generated specifically for the purposes of the Hunter subregion Bioregional Assessment. One output of the landscape water balance model (AWRA-L), is a gridded surface of deep drainage, which can be equated to recharge (see companion product 2.6.1 for the Hunter subregion (Zhang et al., 2016)). The chloride mass balance method (Anderson, 1945) has been used to estimate a recharge surface for the Hunter subregion (see Section 2.1.3 of companion product 2.1-2.2 for the Hunter subregion (Herron et al., 2016)).
Groundwater use
Figure 11 shows the distribution of bores across the Hunter subregion, classed by purpose (Bioregional Assessment Programme, Dataset 2; NSW Office of Water, Dataset 5). Bores for irrigation water use are concentrated along the main rivers; town water supply bores are localised, but with a high number in the populated areas along the coast; domestic and stock bores are scattered across the subregion and mining bores occur at various locations across the subregion.
Table 12 shows the licensed entitlement volumes grouped by purpose (basic water rights under the Water Act are not included). Of the 128.46 GL/year of licensed groundwater entitlements, mining has the highest share with 51.08 GL/year (40%), followed by irrigation bores with an estimated volume of 46.17 ML/year (36%). Most of the remainder support town water supply, domestic and stock uses or have an unspecified use.
Data: Bioregional Assessment Programme (Dataset 2); NSW Office of Water (Dataset 5)
Very little metered data are available to quantify actual extraction volumes. The licensed entitlement volumes represent the maximum permissible take from a groundwater source, rather than the actual take in any given year. Estimates of use based on these volumes will likely over-estimate actual use in any given year, as rates of extraction tend to be lower than the permissible take (S Realica-Turner (DPI Water), 2015, pers. comm.).
In addition to use under licensed entitlement, there are many groundwater bores that supply water for domestic and stock use under a basic water right, for which an annual volume of take is not specified. As previously stated, estimates of take for domestic and stock use are assumed to be 2 ML/year per bore, or not more than 4.8 GL/year across all domestic and stock bores.
Table 12 Groundwater entitlements by licensed purpose for the Hunter subregion
amay also include exploration
bmay also include industrial
cmay also include mining
ddoes not include basic water rights
Data: Bioregional Assessment Programme (Dataset 2)
