Definition of surface and groundwater resources; their availability and quality

Assessment of surface and groundwater sustainable yield

Product 1. Water availability and sustainability

Most rivers in Australia's rangelands are ephemeral and so water used is mainly derived from local run-off or groundwater. Pastoral rangelands use natural and artificial watering points that are typically less than 10 km apart. These provide water for not only domesticated stock but also for native and feral grazing animals. This can lead to intensive grazing near watering points and potential threats to biodiversity (Landsberg et al. 1997).

Information available in the Atlas for each groundwater management unit

Water availability

• Developed yield (average annual volume that can be abstracted for use by existing infrastructure measured in megalitres per year [ML/yr])
• Abstraction (average annual volume currently extracted for use measured in megalitres per year [ML/yr])

Aquifer characteristics

• Depth (average depth to aquifer)
• Thickness (thickness of strata)
• Salinity (salt concentration as measured by electrical conductivity in microSiemens per centimetre [µS/cm)
• Bore levels (monthly hydrographs)

The Great Artesian Basin

The Great Artesian Basin is one of the world's largest aquifer systems. It covers an estimated 1.7 million km² and stores 8 700 000 GL. Each year the Great Artesian Basin supplies 570 GL of water for a variety of uses-mainly grazing and mining.

Management of the groundwater resource of the Great Artesian Basin is shared between Queensland, New South Wales, South Australia and the Northern Territory. The Strategic Management Plan (Great Artesian Basin Consultative Committee 2000) provides for its management as a single resource, including continued bore rehabilitation and piping of bore drains (costed at approximately $220 m) to minimise waste from previously free-flowing bores in the Great Artesian Basin. Further work required includes:

• recovering artesian pressure to achieve pastoral and biodiversity outcomes;
• making water available for new users; and
• reducing adverse impacts of water distribution on natural resources and biodiversity.

Water use in the Great Artesian Basin exceeds State and Territory sustainable estimates (Figure 3).

Estimates of sustainability - Great Artesian Basin use profile-indicating priority areas for investment in bore rehabilitation and piping of bore drains.

Estimates of sustainability

A four-class classification system was developed to provide a simple method to communicate the status of the use and allocation of Australia's water resources.

* Water extraction as a percentage of sustainable yield

Category 1 systems have zero to low levels of resource use: direct management intervention and information requirement are low.

Category 2 systems are moderately developed: management intervention and resource information requirement is moderate.

Category 3 systems are close to, or at, their extraction limit and require a high level of management inputs. Resource information and monitoring are vital for these systems.

Category 4 systems are over-committed in water allocation and/or use: insufficient provision has been made for environmental and non-consumptive uses, management intervention and information requirements are substantial.

Figure 3. Groundwater management units in each abstraction development category (2000).

Excerpt from Australian Water Resources Assessment 2000 (National Land and Water Resources Audit 2001a)

Great Artesian Basin groundwater province summary data

Estimates of data reliability

Landscape function versus condition

Landscape function and land condition are separate measures.

• Landscape function is characterised by the interrelationships of landscape components in relation to changes in energy and materials in space and time. Assessment of landscape function is a necessary precursor to a judgement of condition.
• Condition of a landscape is a value judgement and is related to its worth for a particular land use. It can be influenced by preconceptions, and cultural and social views (Figure 4).

Rangeland vegetation

Most rangeland vegetation is dominated by native species.

In northern and eastern Australia the dominant vegetation types are eucalypt woodland with a grassy understorey, eucalypt forest and acacia woodland with a grassy understorey, and open grasslands. The distribution of forest and woodland is determined by rainfall effectiveness and soil type-little water, higher evaporation rates and low fertility limit the height and density of trees.

Remote sensing is a good monitoring tool because:

• image databases are made up of objective, consistently processed data;
• it allows monitoring at a range of scales and across environments;
• it can be integrated with ground data to detect change and identify function in rangelands (Figures 8, 9 & 10); and
• it is cost-effective, providing an ability to regularly monitor large areas and store a large amount of information on Australian landscapes.

Relationships between ground monitoring and remote sensing techniques are important. They enable an understanding of how landscapes respond to disturbance and variable seasons over a long period, and allow comparison between functional and dysfunctional landscapes.

Figure 8. Landsat-derived vegetation cover map at the paddock scale in the Stony Plains bioregion (March 1988).

The location of the photograph is marked by the white square on the image.

A uniform cover of bladder saltbush (Atriplex vesicaria) and scattered dead finish (Acacia tetragonophylla) occurs on the Gibber plain on the left hand side of the fence, with barley Mitchell grass (Atrebla pectinata), feathertop wiregrass (Aristida latifolia) and common bottlewashers (Enneapogon avenaceus) on the more heavily grazed right hand side of the fence. Grazing by cattle only occurs in this area for short periods when surface water is available.

To the right side of the fence, the bladder saltbush has been substantially reduced by intense grazing from sheep and cattle over several decades. The image indicates cover differences. Interpretation of causes and effects on plant communities is provided by integrating remote-sourced data with ground data.

Source: Brook et al. 2001.

Figure 10. Regional trend for the Ord Victoria Plains bioregion in north-west Australia.

Light green represents areas where cover increased; dark green represents areas with stable cover; red represents areas where cover decreased. In this example, fire scars have not been removed and much of the red is attributed to burnt country. Fire history maps overlain on this image would aid in interpreting landscape condition.

These data show that cover has increased over much of the region. This trend can be attributed to a run of good seasons from 1993 to 1997. This is also consistent with the interpretation of ground data collected at monitoring sites over the same period.

Source: Karfs et al. 2000

Change in landscape function from monitoring site data

At the site scale, landscape function can be directly assessed using the Landscape Function Analysis approach. A range of attributes can be used to provide an indication of landscape function. One example is that the frequency and change in frequency of perennial species can be used to provide a broad estimate of the ability of the landscape to regulate nutrients and water (Table 2); soil or vegetation cover could also be used in this example (Figure 12). The specific attribute used will depend on the objective of the analysis.

Product 3. Change in biological diversity

P.M. Byrne describing Charlotte Waters 1921, (quoted in Calaby 1996)

Native vegetation

The benefits of tracking changes in Australia's native vegetation are far from well documented. However the link between vegetation and animal biodiversity is well recognised (e.g. in the southern arid zone there is a direct link between vegetation and animal biodiversity):

Reid & Fleming 1992

The major threats to native vegetation are grazing by stock and feral animals, and change in fire frequency (Figure 13).

FLINDERS LOFTY BLOCK

Changing biodiversity and threatening processes within a bioregion

Major land uses

Extensive grazing by sheep is the dominant land use and has been since the 1840s. Agriculture (mainly wheat) and mining (including coal and copper) have historically been important. Tourism is now a major industry.

Conservation areas

Although 10% of the bioregion is protected in conservation areas, these include only 14 of the 49 recognised environmental subregions.

Condition and threats

Overgrazing by sheep, rabbits and goats has led to degradation, including lack of regeneration for a range of woody plant species.

Eight exotic animal species (rabbit, fox, cat, goat, black rat, house mouse, donkey and brown hare) are established in the bioregion. Rabbits (arriving in approximately 1880) and foxes (1900) have been extremely common until release of the calicivirus.

The understorey of many vegetation associations (e.g. white cypress pine Callitris glaucophylla woodland and tussock grasslands) is now mostly made up of exotic plant species, especially where stock have grazed heavily. One hundred and twenty-three exotic plants have been recorded in the greater Flinders Ranges area including rosy dock (Acetosa vesicaria), Salvation Jane or Patterson's curse (Echium plantagineum), red brome (Bromus rubens), ward's weed (Carrichtera annua), Maltese cockspur Centaurea melitensis, common storksbill (Erodium cicutarium), spiked malvastrum (Malvastrum americanum), Schismus barbatus, smooth mustard (Sisymbrium erysimoides), common sow thistle (Sonchus oleraceus), onion weed (Asphodelus fistulosus), horehound (Marrubium vulgare) and woolly burr-medic (Medicago minima).

Changes in biodiversity

Mammal fauna has suffered major losses, mainly in the regional extinction of 24 out of the 50 mammal species. These include small macropods, bandicoots, dasyurids, bats and rodents. Until recent control of rabbits, foxes and goats, the yellow-footed rock wallaby (Petrogale xanthopus) was continuing to decline.

Three plant species are believed to have become extinct in the Flinders Ranges: reed bent-grass (Deyeuxia quadriseta), blunt pondweed (Potamogeton ochreatus), and Pilularia novae-hollandia.

GULF PLAINS

Changing biodiversity and threatening processes within a bioregion

Major land uses

The dominant land use is cattle grazing on native pastures, dating back to the 1860s. Mining continues to be a significant industry.

Conservation areas

Two point five percent of the Queensland part of the bioregion is in conservation reserves. None of the Northern Territory portion is reserved.

Condition and threats

Of the 83 regional ecosystems defined for the Queensland part of this bioregion, three are considered endangered and 26 are considered of concern. Most (72%) of those that are endangered and of concern are associated with watercourses and flood plains.

Sattler & Williams 1999

Changes in biodiversity

Major declines and local extinctions of the golden-shouldered parrot (Psephotus chrysopterygius) have occurred across the Gulf of Carpentaria part of its range. This decline has been attributed to habitat change (principally invasion of grassland areas by melaleucas) caused by altered fire regimes over the last century. No plant species are known to have become extinct in this bioregion.

GREAT VICTORIA DESERT

Changing biodiversity and threatening processes within a bioregion

Major land uses

The Great Victoria Desert is sparsely inhabited. Most of the area is Indigenous land-in some cases tenured as conservation reserve. A network of exploration lines was surveyed and cleared across large areas during the late 1960s and early 1970s. Mineral exploration continues. Parts of the bioregion were used as restricted area for the Woomera Rocket Range, for nuclear testing and as storage for spent atomic fuels. Pastoral leases exist in the less arid margins.

Conservation areas

The 'Unnamed Conservation Park' in the South Australian portion of the bioregion is one of Australia's largest (21 327 km²) conservation reserves. More than 10% of the South Australian and 5-10% of the Western Australian parts of the bioregion are in conservation reserves.

Condition and threats

The impacts of rabbits and pastoralism on land condition resulted in fewer perennial species and lower plant density especially for the most susceptible vegetation type-chenopod shrublands.

Greenslade et al. 1986

Changes in biodiversity

Reptiles are a feature of this bioregion with relatively intact populations. Two snake species (the desert death adder [Acanthophis pyrrhus] and western black-naped snake [Neelaps bimaculatus]) have not been observed in the South Australian part of the bioregion for about 60 years-a possible decline that may be of concern.

One-third of mammal species have become extinct in this bioregion during the last 40 years including the numbat (Myrmecobius fasciatus), bilby (Macrotis lagotis), burrowing bettong (Bettongia lesueur) and stick-nest rats (Leporillus spp.).

Some bird species are declining, including mallee fowl (Leipoa ocellata) and scarlet-chested parrot (Neophema splendida). Comparison of recent bird records with those reported between 1873 and 1945 suggest that Australian bustard (Ardeotis australis), bush stone-curlew (Burhinus grallarius) and spinifex pigeon (Geophaps plumifera) have declined.

The decline in species is occurring in both non-pastoral and conservation areas. This highlights the need to reduce feral animal populations as part of protective management activities across all tenures.