SoE 2003 > Water > 5.4 Groundwater extraction

5.4 Groundwater extraction

Some groundwater resources in NSW are not being used sustainably or are at risk of over-extraction

Demand for groundwater resources in NSW has increased substantially as the limits of surface water supply are reached. Some groundwater resources are being used beyond their sustainable yield or are under threat of over-extraction.

Groundwater management areas where over-extraction is occurring are the Lower Namoi and the Great Artesian Basin. Areas at risk of over-extraction include the Murrumbidgee, Macquarie–Bogan, Lachlan, Hunter, Lower Murray, Upper Namoi, Lower Gwydir and Peel River groundwater systems. It is clear that there is little or no potential for further commitment of ground water in these areas.

The recent development of statutory groundwater-sharing plans is a significant step forward.

NSW Indicator

Importance of the issue

Many ecosystems in NSW require ground water for their ongoing health and maintenance. These include surface water bodies, such as wetlands, rivers and lakes, which are connected to ground water, and terrestrial ecosystems.

Ground water is a vital resource, particularly where surface water supplies are limited. More than 200 towns in NSW use ground water as their principal source of water and many regional economies rely on its availability. Approximately 11% of the water used in NSW for drinking, irrigation, watering stock, and domestic and industrial purposes comes from groundwater sources. This is expected to increase because most of the State's surface water resources are fully committed for extractive and other uses.

Changes in climatic conditions affect the amount of ground water used. Extraction may increase substantially in times of drought to offset the lack of surface water available, while in periods of high rainfall, ground water may not be used at all.

Over-extraction of ground water potentially places pressure on dependent aquatic and terrestrial ecosystems because it:

• reduces base flows to rivers and decreases the water available to other groundwater-dependent ecosystems
• alters water quality by inducing more saline water into an aquifer
• reduces the amount of ground water available for future extraction.

For more information on ground water, see EPA 2000c.

Groundwater use in NSW

As the limits of surface water supply are being reached in NSW, demand for groundwater resources has increased substantially. Across NSW, groundwater use increased 217% between 1983–84 and 1996–97 from 318 gigalitres (GL) per year to 1008 GL (NLWRA 2001b). This represents the largest increase in groundwater use of any Australian State or Territory.

The most recent data on groundwater use in NSW is for 1996–97, as reported by the National Land and Water Resources Audit (NLWRA 2001b). Table 5.5 shows the mean groundwater use by economic sector for this period. Of the total ground water used in NSW, 64% was for irrigation, 20% for non-irrigation rural uses, and 16% for urban/industrial purposes.

Table 5.5: Mean annual groundwater use in NSW, 1996–97

Source: NLWRA 2001b

To assess the sustainability of groundwater use, extraction levels need to be compared with the sustainable yield. The sustainable yield is that proportion of the long-term average annual recharge (the infiltration of surface water into ground water) that can be extracted each year without causing unacceptable impacts on the environment, aquifer integrity, or other groundwater users.

In the past many of the State's groundwater systems have been over-allocated, with the sum of all entitlements exceeding the sustainable yield. To date, however, the quantity of water actually extracted in most groundwater systems is generally less than or close to the sustainable yield, because many groundwater users do not take up their whole allocation.

Map 5.3 shows the relationship between water use and sustainable yield. Areas where over-extraction has occurred include the Lower Namoi Alluvium and the Great Artesian Basin. Areas at risk from over-extraction include groundwater management areas in the Murrumbidgee, Macquarie–Bogan, Lachlan, Hunter, Lower Murray, Upper Namoi, Lower Gwydir and Peel River catchments. There is little or no potential for further commitment of ground water in these areas.

Map 5.3: Groundwater use compared with sustainable yield for NSW Groundwater Management Areas

Source: DLWC data, as at July 2002

Note: Because only high-yield bores are required to be fitted with a meter, some usage data has been estimated.

Response to the issue

The major response to the pressures on groundwater resources has been to ensure that allocations for extraction do not exceed sustainable yields. The primary mechanisms for achieving this have been licensing of groundwater systems and implementation of water-sharing plans for specific areas and aquifers.

The Water Management Act 2000 requires all aquifers to be managed within their sustainable yield. Groundwater-sharing plans are being developed and implemented by local groundwater management committees for areas of significant groundwater use or where groundwater resources require protection. The beneficial use of each aquifer has been determined and strategies are to be put in place to protect the aquifer.

The following aquifers have been identified as most at risk and statutory groundwater-sharing plans have been developed for them:

• Lower Gwydir
• Lower Lachlan
• Lower Macquarie
• Lower Murrumbidgee
• Upper and Lower Namoi
• Tomago–Tomaree–Stockton.

The following areas are not over-allocated but have had management plans developed because of potential water quality threats as each is an important local water source:

• Stuarts Point
• Alstonville Basalt
• Kulnura–Mangrove Mountain
• Dorrigo Basalt.

Draft plans are already well advanced for the Great Artesian Basin and Lower Murray aquifers and plans will be developed for additional aquifers in coming years. All plans are intended to achieve sustainable extraction within the 10-year life of the plan.

The licensing of ground water up to the sustainable yield by the Department of Infrastructure, Planning and Natural Resources is also continuing for areas not yet covered by groundwater-sharing plans.

There are also a number of policies relating to ground water developed within the framework of the NSW Groundwater Policy including:

• the NSW Groundwater Quality Protection Policy adopted in December 1998, which states that ground water must be managed to maintain the beneficial use of all NSW groundwater systems (DLWC 1999b)
• the NSW Groundwater-dependent Ecosystems Policy, adopted in April 2002.

Other programs to manage ground water include assistance schemes to promote efficient water use by irrigators (see Water 5.2) and work to improve understanding of the relationship between surface and ground water and the impact of groundwater extraction on river systems. A system of central reporting for groundwater resources is also being developed.

Effectiveness of responses

The recent development of statutory groundwater-sharing plans is a significant step forward in managing this resource. However, as water reforms are being phased in over a 10-year period, there will be some areas where ground water is used beyond its sustainable yield in the short term.

The water reform process has increased awareness of groundwater issues in the community and there is now general consensus that its use must become more sustainable. Current activity is focused on the difficult transition to achieve these sustainable levels.

Future directions

There is a need to better quantify groundwater use and recharge, introduce new mechanisms for allocation within the sustainable yield for more groundwater sources, and improve the efficiency of groundwater use.

Reducing water consumption will be crucial to achieving sustainable groundwater management. Agriculture, industry and government all need to find ways to facilitate more efficient use of water. Water efficiency measures for urban areas are outlined in Human Settlement 2.2. For agricultural activities, several assistance schemes are in place to promote efficient water use by irrigators, as discussed in Water 5.2.

More transparent and reliable metering needs to be available for all significant groundwater uses to track progress in water efficiency. Currently only high-yielding bores must be fitted with a meter. This requirement needs to be enforced in priority aquifers. Although the quality of data on groundwater use has improved recently, more information is needed to fully assess the status of ground water and ensure that the resources are appropriately managed.

A better understanding is required about how the quantity of ground water affects the health of ecosystems which depend on it. Little is known about the fauna and flora that live within aquifers or the volume of water they require. This makes it difficult to manage groundwater systems appropriately for the conservation of dependent biota.

Monitoring and reporting against performance indicators specified in groundwater-sharing plans should provide better information on the socioeconomic and ecological impacts of managing the use of ground water within sustainable yields.

Linked issues

2.1 Population and settlement patterns

4.1 Land-use changes

5.1 Freshwater riverine ecosystem health

5.2 Surface water extraction

5.5 Groundwater quality

6.6 Aquatic ecosystems

6.7 Aquatic species diversity