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Water chapter 4


4.4 Groundwater

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Water

4.4 Groundwater

Demand for assigned groundwater resources in New South Wales has eased significantly in recent years as more surface water has become available following high rainfall. Water sharing plans continue to be implemented for groundwater aquifers, with 34 now completed and all NSW sources in the Murray–Darling Basin to be covered by the end of 2012.

Overall groundwater use fell considerably during the 2010–11 water year, with extraction from most groundwater sources well below the long-term sustainable extraction limit. Groundwater levels have risen in most areas in response to the higher rainfall, enabling aquifers to recharge and usage levels to drop.

During 2010–11, the Lower Gwydir and parts of the Upper Namoi groundwater sources experienced the highest levels of groundwater demand, due to the relatively drier conditions being experienced in northern inland NSW.

The most significant fall in groundwater use occurred in the Lower Murrumbidgee and Lower Murray Groundwater sources due to the flooding experienced in southern NSW in late 2010–early 2011.

Water sharing plans set annual extraction limits for groundwater use. Extraction from some groundwater sources has been above the long-term sustainable yield in the recent past, but use is now being managed to align with the sustainable yield through the implementation of water sharing plans.

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NSW indicators

Indicator and status

Trend

Information availability

Extent and condition of groundwater-dependent ecosystems

Unknown

limited

Long-term extraction limit: use

Decreasing

resonable

Long-term extraction limit: entitlement

Decreasing

good

Aquifer integrity

Stable

resonable

Groundwater quality

Stable

resonable


Notes: Terms and symbols used above are defined in About SoE 2012 at the front of the report.


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Introduction

Where surface water is available, groundwater is generally seen as a supplementary water resource. However, for many communities in regional NSW, groundwater is the primary source of water for drinking, domestic and stock use, and it is also used in agriculture and industry.

A range of ecosystems also depend on groundwater for their continued survival, including some highly specialised and endemic subterranean systems, as well as surface water bodies (wetlands, rivers and lakes) that are connected to groundwater and some terrestrial ecosystems.

Significant changes in the quality and quantity of groundwater available have the potential to degrade ecosystems and affect human uses of water. Because of the hidden nature of many groundwater-dependent ecosystems, the impacts on these systems are likely to be less obvious and understood.

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Status and trends

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Extent and major uses of groundwater in NSW

Approximately 11% of all water used in NSW comes from groundwater sources. It is used for drinking water, irrigation, watering stock, and domestic and industrial purposes. For more than 200 towns in NSW, groundwater is the principal source of water supply. An estimated 13% of the groundwater used in NSW goes to domestic and stock purposes.

However, agriculture is the largest user of groundwater in NSW with the greatest volume of use being for irrigation in the areas of the main inland alluvial aquifers. This is followed by mining, with groundwater being the only available source of water for some inland mining operations, although it can also be an obstruction or hazard that must be removed for mining to proceed.

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Levels of extraction and recharge

Variability in climatic conditions affects the amount of groundwater used. Extraction may increase substantially in times of drought to offset the lack of surface water, while in periods of high rainfall and associated recharge less groundwater is used. Due to high rainfall and an increase in surface water availability, demand for groundwater resources has decreased over the past three years, following an extended period of high demand.

Figure 4.6 shows groundwater extraction from all metered aquifers in NSW and the major inland alluvial aquifers over the 10 years to 2010–11. Two peaks in extraction occurred in 2002–03 and 2006–07 when drought conditions were particularly acute. A gradual decline in extraction has occurred since 2006–07 as the effects of the drought eased, but also due to the introduction of water sharing plans in several of the large inland alluvial groundwater sources since 2006. A further substantial reduction occurred in the 2010–11 water year, due to very high rainfall and flooding in many areas. Overall only 350 gigalitres (GL) was extracted in 2010–11, around a third of the volume used when demand was at its peak.

Figure 4.6: Annual levels of groundwater extraction from metered aquifers in NSW and the major inland alluvial aquifers, 2001–02 to 2010–11

Figure 4.6

Download Data

Source: NSW Office of Water (NOW) data 2011

Notes: The major inland alluvial aquifers are the basins of the Gwydir, Namoi, Macquarie, Lachlan, Murrumbidgee and Murray rivers.
The purple line is the long-term average annual extraction limit (LTAAEL) for these major groundwater sources only, which is the level of water that can be extracted annually on a sustainable basis over a longer time frame. The LTAAEL does not apply to all metered extraction in NSW.
Extraction limits are being reduced gradually to align with the LTAAEL by the final year of relevant water sharing plans in 2016–17, so extraction levels for the major inland alluvial aquifers are permitted to exceed the LTAAEL until then.


Around 80% of metered groundwater use in NSW occurs in the six major inland alluvial aquifers of the Gwydir, Namoi, Macquarie, Lachlan, Murrumbidgee and Murray River valleys as shown in Figure 4.6. The overall volume of groundwater extracted in NSW is higher as extraction is not metered in many areas of NSW where groundwater demand is low, particularly on the coastal side of the Great Dividing Range.

A groundwater hydrograph from a monitoring bore located in the largest groundwater source in NSW – the Lower Murrumbidgee deep aquifer – illustrates the general pattern of groundwater response to climatic conditions and variations in groundwater demand (Figure 4.7).

Groundwater use in this area began in the late 1970s and early 1980s, with an annual pattern of drawdown over the spring and summer, followed by recovery during autumn and winter, restoring previous levels by late winter. However, as demand grew and water pumping increased, drawdowns became deeper and seasonal recovery incomplete. As drier conditions set in, very deep drawdowns occurred, with the most acute in the summer of 2006–07 when it became clear that such levels of extraction could not be sustained in the longer term. In the years that followed, a reduction in use coincident with higher rainfall resulted in some recovery of levels, until 2010–11 when groundwater levels rose significantly. However, levels have not returned to pre-development levels and are not expected to do so.

Figure 4.7: Groundwater hydrograph for a monitoring bore in the Lower Murrumbidgee deep groundwater source (GW036358)

Figure 4.7

Download Data

Source: NOW data 2011


Long-term average annual extraction limits

The intent of water sharing plans for groundwater (see 'Responses' below) is to manage the resource sustainably so that groundwater levels do not decline excessively, causing unacceptable impacts on the aquifer or groundwater-dependent ecosystems, and extraction remains in balance with recharge over the longer term. This means that extraction above sustainable levels in times of drought, for one or several years, will result in a decline in groundwater levels with recovery occurring during wetter periods when recharge is much greater than extraction. This natural variability of groundwater systems provides for a reliable and secure water resource.

The long-term average annual extraction limit (LTAAEL) is the average level of groundwater that can be extracted sustainably on an annual basis over a longer term from the groundwater sources defined in water sharing plans. It is effectively the plan 'limit'. Where data is available, the extraction limit is based on numeric models which relate rainfall and river leakage to recharge over a period of 20 to 30 years. Where insufficient data is available, it is based on a percentage of the annual average rainfall being captured as recharge. The final extraction limit is then set after a portion of groundwater is allocated to the environment, based on the environmental assets identified as requiring protection.

In large areas of NSW the potential to extract groundwater is low because of hydro-geological factors or the quality of the water is not suitable for use. At the state scale, therefore, the overall level of entitlement compared with the LTAAEL is quite low, at around 25%.

The inland alluvium geological provinces lie in the flat lands of north-western and south-western NSW and provide high-yielding, good quality water supplies which are able to be used extensively for irrigation. About 98% of all metered groundwater extraction in NSW is from these aquifers, including the six major aquifers referred to in Figure 4.6, which provide 80% of extraction. As a consequence, it is mainly in the inland alluvium that there is pressure to manage groundwater sustainably as extraction is close to the LTAAEL.

From the early 1980s, embargos have been imposed on the issue of further licences in the inland alluvial aquifers and annual limits have been placed on extractions. Since 2006, water sharing plans have placed a formal limit on extraction enforced through regulation. The implementation of these plans has expanded to areas beyond the six major inland alluvial aquifers, with all inland NSW groundwater sources to be covered by the end of 2012 (see below under 'Responses').

Extraction compared to extraction limits

Groundwater use can be quite variable, both within and between groundwater sources. In some years and some groundwater sources, extraction can exceed the LTAAELs that are set in water sharing plans. To address historical over-allocation, water sharing plans provide for a progressive reduction in water allocations over their 10-year term. At the end of their terms, water sharing plans will ensure that average annual groundwater use will be within the LTAAEL.

Map 4.4 shows groundwater use during the 2010–11 water year as a percentage of the LTAAEL, which provides an indication of sustainable use in areas where groundwater use is metered and monitored. The very wet water year caused groundwater demand to fall significantly with use at, or well below, the LTAAEL in most areas. The highest levels of extraction were from the Lower Gwydir groundwater source around Moree at 102% of LTAAEL. This level is within the acceptable buffer allowed in the water sharing plan and does not exceed the interim extraction limit set annually while long-term levels of use are adjusted to align with the LTAAEL. The only other area where use was greater than 50% of the LTAAEL was in some groundwater sources of the Upper Namoi around Narrabri. Usage was highest in these areas due to the relatively lower rainfall in northern inland NSW during 2010–11. The greatest falls in demand were in the groundwater sources of the Lower Murrumbidgee (around Hay) and Lower Murray (around Deniliquin) because of very high rainfall and flooding which occurred in southern NSW.

Map 4.4: Extraction from NSW groundwater aquifers as a percentage of the long-term average annual extraction limit, 2010–11

Map 4.4

Notes: Only those areas of NSW where groundwater use is metered are shown on the map.
LTAAELs for the six major inland alluvial water sources are being reduced during the life of their respective water sharing plans. Usage is compared with the LTAAEL applicable for the 2010–11 water year, not the LTAAEL specified for the end of the plan (at year 10).


Some areas outside the six major alluvial groundwater sources have entitlements higher than the extraction limit, but use is currently at or below the limit. Where use approaches the extraction limit due to the activation of previously unused entitlements, the water sharing plan allows for usage to be moderated by determining the water levels available for extraction.

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Groundwater-dependent ecosystems

Groundwater-dependent ecosystems (GDEs) are described in water sharing plans for groundwater as those where species composition or natural functions depend on the availability of groundwater. Dependence may be complete or partial, such as during periods of drought. The degree and nature of dependency influences the extent to which ecosystems are affected by changes to water quality or quantity in groundwater aquifers.

GDEs occur across a broad range of environments, from highly specialised subterranean ecosystems to more generally occurring terrestrial, aquatic and marine ecosystems. GDEs were first identified and classified in Australia in the late 1990s (Hatton & Evans 1998) and were subsequently recognised in NSW by the NSW State Groundwater Dependent Ecosystems Policy (DLWC 2002). Since the release of this policy, the number of GDE types has grown as knowledge has improved.

There are two main groupings of GDEs – subsurface ecosystems and surface ecosystems – and seven broad types overall based on ecological, geomorphic and water chemistry criteria, as described below.

Subsurface ecosystems

The most significant, diverse and potentially sensitive groundwater-dependent organisms are those found underground within aquifers and cave ecosystems. These organisms are totally reliant on groundwater and are adapted to these environments (Gibert et al. 1994).

Karsts and caves are defined as 'natural cavities in rock which act as a conduit for water flow between input points, such as stream sinks, and output points, such as springs or seeps' (White 1984). Karsts are a specific form of cave terrain with distinct landforms and drainage characteristics. The aquatic ecosystems within these subterranean environments consist of communities of organisms, mainly microorganisms and invertebrates that are adapted to live in perpetual darkness and are totally dependent on groundwater (Ward et al. 2000). Life forms that exist in caves and aquifers are considered to be highly endemic.

Subsurface phreatic aquifer ecosystems: The free water within the pore spaces and cracks of unconsolidated sand and gravel and fractured rock aquifers can also support communities of diverse, endemic, highly specialised, and often relict life forms. These can include microorganisms, invertebrates and, occasionally, vertebrate species. Due to their adaptation to a relatively narrow natural range of water chemistry, these communities may be of interest as indicators of groundwater health and water quality.

Subsurface baseflow streams: Many river reaches have a baseflow component derived from groundwater discharge which is vital to the character and composition of in-stream and near-stream ecosystems. By providing a permanent water source, baseflow streams support ecosystems that are able to live in subsurface sediments (Evans 2007).

Surface ecosystems

Surface baseflow streams also support surface ecosystems through surface flows or permanent pools that provide refuges in times of low flows.

Wetland ecosystems may depend on groundwater to maintain seasonal patterns of waterlogging or flooding. Wetlands provide the most extensive and diverse set of potential GDEs in Australia (Hatton & Evans 1998). Examples include paperbark swamp forests and woodlands, swamp sclerophyll forests and woodlands, swamp scrubs and heaths, swamp shrublands, sedgelands and mound spring ecosystems.

Estuarine and near-shore marine ecosystems: Many of these systems depend on groundwater discharges to provide suitable habitats for a diverse group of flora and fauna. These include coastal lakes, mangroves, saltmarshes and seagrass beds (Hatton & Evans 1998; SKM 2001; Burnett et al. 2003). Groundwater discharges may be in the form of direct off-shore discharge zones called 'wonky holes', diffuse discharges through sandbeds, or baseflow streams that discharge to the ocean.

Groundwater-dependent or phreatophytic vegetation: This is terrestrial vegetation that depends on the subsurface presence of groundwater, often accessed via the capillary fringe – the subsurface layer just above the watertable that is not completely saturated (SKM 2001; Eamus et al. 2006). This vegetation may be dependent on groundwater to sustain transpiration and growth through a dry season or maintain perennially lush ecosystems in otherwise arid environments.

Although not a specific GDE type, terrestrial fauna may also depend on groundwater as a source of drinking water.

Identification of groundwater-dependent ecosystems

Interest in GDEs and their sustainability is relatively recent and little is known about their location or condition (Eamus & Froend 2006). However, the NSW Government has been actively engaged in identifying GDEs across the state in recent years. A preliminary desktop study identified a range of GDEs and sites where they could potentially occur. Areas of terrestrial vegetation that are potentially groundwater-dependent are being mapped using satellite imagery (MODIS). Follow-up field survey work will establish the extent of their natural values and the condition of these sites, as well as their level of dependence on groundwater.

Risk assessment guidelines to provide methods for identifying and valuing GDEs and their associated aquifers (Serov et al. 2012) have now been developed during assessment of the coastal sands and floodplain alluvium on the NSW coast. The guidelines enable the development of management strategies for aquifers and GDEs and assessment of the potential and actual impacts of proposed activities on GDEs.

Map 4.5: Mapped NSW groundwater-dependent ecosystems at December 2011

Map 4.5


High priority GDEs shown in Map 4.5 have high ecological value and are mostly associated with springs and karsts, but may include other GDEs identified as high priority in water sharing plans. At this stage, mapping of GDEs with high ecological value has only occurred along the coast. Map 4.5 also displays high probability GDEs within the Central West Catchment Management Authority area but the ecological value of many of these communities is yet to be determined. Current mapping is still limited and will be expanded in future.

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Pressures

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Excessive demand and extraction

Over the longer term, reducing the storage levels of an aquifer or permanent mining of the resource will affect its stability and integrity, as well as having permanent consequences for all dependent ecosystems and beneficial uses. Competition for groundwater resources can place the long-term security of these resources at risk.

NSW groundwater sources have been assessed for risk due to groundwater demand using a standard developed under the National Framework for Compliance and Enforcement Systems for Water Resource Management, agreed to by COAG in December 2009. The areas at highest risk are characterised by high consumption with entitlements close to or above extraction limits and actively protected water rights. The areas of lower risk are those where demand is low and entitlements are significantly below sustainable levels.

The outcome of the risk assessment is shown in Map 4.6.

The areas at highest risk are:

  • Lower Murrumbidgee around Hay
  • Mid-Murrumbidgee around Wagga Wagga
  • Lower Namoi, west of Narrabri
  • Lower Gwydir around Moree
  • parts of the Lower Macquarie, west of Dubbo
  • Orange basalt
  • alluvial valleys of the Hunter catchment
  • coastal sand beds north of Newcastle.

Map 4.6: Risk posed to groundwater due to groundwater demand

Map 4.6

Although the risk assessment was intended to guide the prioritisation of water compliance resourcing, it has also highlighted the most important and sensitive areas for broader decision-making on groundwater management. The aim of water sharing plans is to ensure that water is managed sustainably and plans will shortly be in place in all these areas to protect the long-term security of groundwater supplies.

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Saline intrusion

Where the level of extraction of groundwater is high and the aquifer is overlain by saline aquifers or near the coast, there is a risk of saline water intrusion into the depleted aquifer. This will have a detrimental effect on water quality and related uses. The intrusion of sea water is relevant particularly to the coastal sand beds north of Newcastle, which are an important source of water for the Greater Newcastle area.

Studies have recently been completed to assess the risks caused by high volume groundwater extraction on groundwater quality in the six major inland alluvial aquifers. Localised areas of water quality decline have been discovered and strategies are being developed to address those areas of risk. The water sharing plans contain provisions to ensure groundwater quality does not change to a less beneficial risk class.

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Chemical contamination

Groundwater contamination by chemical pollutants can significantly reduce the value of water to users or the environment and increase the cost of water treatment. It may prevent some types of water use altogether. Once an aquifer is polluted, it is extremely difficult and expensive to restore. Groundwater contamination is largely associated with long-standing existing or former industrial areas and tends to be in urbanised areas concentrated around Sydney, Newcastle and Wollongong.

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Climate change

The Sustainable Yields Assessment Project for the Murray–Darling Basin (CSIRO 2008a) identified that the current and probable future levels of groundwater extraction will have a greater impact on inland aquifer systems than a likely reduction in recharge from rainfall and river systems due to climate change. Along the coast, the potential impacts of sea level rise and climate change on coastal aquifers will be more significant with saline intrusion on freshwater coastal aquifers affecting associated groundwater-dependent ecosystems.

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Responses

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Established responses

NSW 2021

NSW 2021: A plan to make NSW number one (NSW Government 2011) is the Government's 10-year plan for NSW. Under Goal 22 – 'Protect our natural environment', the plan contains the following target: 'Improve the environmental health of wetlands and catchments through actively managing water for the environment by 2021'. Further details on Goal 22 are provided in Water 4.1.

Water Management Act 2000

The Water Management Act 2000 requires all groundwater aquifers to be managed sustainably and this is occurring through the implementation of statutory water sharing plans for groundwater.

Groundwater- dependent Ecosystems Policy

The NSW State Groundwater Dependent Ecosystems Policy (DLWC 2002) provides guidelines on how to protect and manage groundwater-dependent ecosystems. Further work will help to establish the location of these ecosystems and how heavily they rely on groundwater.

Water sharing plans for groundwater

The intent of water sharing plans for groundwater is to manage the resource so that extraction remains in balance with the capacity to replenish them over the longer term.

The environmental provisions in the groundwater sharing plans are centred on:

  • protecting the long-term storage component of the aquifer
  • reserving a proportion of the average annual recharge for the environment.

In some NSW groundwater systems, the level of entitlement is greater than the sustainable yield of the aquifer. The implementation of water sharing plans for all groundwater sources includes a process to manage groundwater use to align with the sustainable yield of aquifers.

This is being achieved by reducing allocations in the six major inland alluvial groundwater sources over the 10-year period of the water sharing plans. Figure 4.8 shows the effect of these reductions in the early years of the plans.

Figure 4.8: Entitlements to groundwater under water sharing plans

Figure 4.8

Download Data

Source: NOW data 2011


There were 34 gazetted water sharing plans which covered groundwater sources as of July 2012, with another six for the remaining inland aquifers to be completed by the end of 2012 and a further 12 plans for coastal aquifers expected to be completed by 2014. In time, all groundwater in NSW will be regulated by water sharing plans made under the Water Management Act 2000 and the Water Act 1912 will no longer apply to groundwater use. The making of these plans will ensure that water entitlements are brought into equilibrium with the sustainable yields of all aquifers throughout NSW.

In the interim, the issue of further entitlements has been embargoed in many areas not covered by a water sharing plan. This is to minimise the risk of resource over-allocation and lessen potential impacts on surface water resources ahead of the making of water sharing plans.

Achieving Sustainable Groundwater Entitlements program

Under this program the Australian and NSW Governments are providing financial assistance to groundwater licence holders and regional communities to help them adjust to reduced groundwater entitlements.

Cap and Pipe the Bores Program

Since the 1990s, various programs have been in place to cap and pipe bores across the Great Artesian Basin, which underlies parts of NSW, Queensland, the Northern Territory and South Australia, to reduce water wastage and improve groundwater pressure. The Cap and Pipe the Bores Program provides financial incentives to landholders to offset the cost of rehabilitating bores and installing efficient piped systems to replace open bores. The pipeline systems provide water to properties, prevent large quantities of salt from entering drainage systems, and help drought-proof properties. These measures have produced savings of 63,000 megalitres (ML) per year and there has now been an increase in water pressure across the basin.

Aquifer protection and research

Great care needs to be taken to ensure that the rapid expansion of mining and coal seam gas developments does not result in permanent damage to aquifers. A new interim aquifer interference regulation took effect on 30 June 2011, which requires new mining and petroleum exploration activities that extract more than 3 ML per year from groundwater sources to hold a water access licence. The NSW Aquifer Interference Policy (DPI 2012) has been developed by the NSW Office of Water as a component of the NSW Government's Strategic Regional Land Use Policy. The new policy details how potential impacts to aquifers, such as those posed by mining and coal seam gas activities, should be assessed and licensed to strike a balance between the water requirements of towns, farmers, industry and the environment.

Significant effort in groundwater research has occurred over the past three years. With the assistance of industry and government partners, NSW has undertaken studies to better understand the dynamics and chemistry of NSW aquifer systems, their hydraulic interaction with rivers, and learn more about groundwater-dependent ecosystems. Some of these studies have been completed and are already influencing decision-making for groundwater management.

This research has been supported by an expansion of groundwater monitoring and improved data management. Monitoring of groundwater levels has increased in sophistication with the roll-out of instruments which measure water levels and transfer the data continuously making it available on the internet.

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Future opportunities

In many groundwater management areas, meter readings are not reported. Current knowledge of groundwater recharge and availability is based on estimates using the limited data available and conceptual models of groundwater recharge. Better monitoring of extraction will improve these models and enable greater accuracy when setting extraction limits.

The connections between groundwater and surface water systems should also be better understood. The potential for holistic management of closely linked systems as a single integrated resource needs further development. There is a risk that more stringent limits on the use of surface water will place greater pressure on groundwater as a substitute source of water.

In making new water sharing plans, the sustainable extraction limit for each water source has been determined for the first time. However, many water sources that are deep or contain brackish groundwater have water that is unassigned. A process is being formulated for the controlled allocation of a proportion of this water where its use would not adversely affect surface water flows, other groundwater users or the environment.

Knowledge of groundwater-dependent ecosystems is still at an early stage and better understanding is needed of their location, characteristics and levels of dependency. Little is also known about the fauna and flora that live within, or are dependent on, groundwater aquifers and this makes it difficult to manage groundwater systems to protect them.

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