Groundwater Resources
Australia has 25 780 GL of groundwater that can be extracted sustainably each year and
is suitable for potable, stock and domestic use, and irrigated agriculture.
Ten percent (2489 GL) is used. Groundwater's importance as a proportion of total use varies
(e.g. in Western Australia groundwater use is twice surface water use; in New South Wales
and Victoria, use is predominately from surface water).
The National Land and Water Resources Audit found that161 (30%) of Australia’s 538 recognised
groundwater management units are either close to or overused when compared with their
estimated sustainable yield. In terms of licences for abstraction, 168 groundwater
management units are either fully allocated or over-allocated when compared with estimated
sustainable yield.
Substantially increased effort by Australia’s water resource managers is required to
precisely define sustainable yield and improve management of Australia’s groundwater
management units.
Priority must continue to be given to the highly- and over-committed groundwater management
units.
Australia has one of the world's larger aquifer systems: the Great Artesian Basin is 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.
Groundwater Resources in the Murray-Darling Basin
There are large resources of groundwater in the MDB. They are present in all three aquifer
types. Covering by far the largest area are the sedimentary basins, in particular the
Great Artesian Basin and the Murray Basin, the major groundwater resources of the MDB.
However, the resources are unevenly distributed and vary in quality.
In spite of their size, the groundwater resources are not unlimited. Many of the
potentially high-yielding aquifers receive a relatively low rate of natural recharge
compared with the volume of groundwater they store. For example, the volume of water
stored in the alluvial sediments in the lower Namoi Valley is about 20,000 GL,
but the average yearly natural recharge is only about 30 GL.
Recharge areas for the various high-yielding alluvial aquifers are the river beds and
flood plains.
For the Great Artesian Basin, the most important recharge areas are the wetter areas
along the Great Dividing Range. For the Murray Groundwater Basin, recharge of the
deeper confined aquifers occurs around the Basin's margins: the shallower unconfined
aquifers also receive recharge over most of their surface areas.
The Great Artesian Groundwater Basin
The Great Artesian Basin (GAB) is one of the largest such basins in the world, with a
total area of 1.7 million km2, covering 22 per cent of Australia.
The Basin extends under the northern part of the MDB in Queensland and New South Wales.
It is a multi-layered aquifer system, consisting mainly of sandstones alternating with
impermeable siltstones and mudstones, and is up to 3,000 metres thick.
The GAB contains an estimated 8,700 million ML of water.
The GAB underlies predominantly arid and semi-arid areas, where surface water resources
are few and extremely unreliable. As a result, it is the only significant source of water
for towns, farms and stock, as well as for mining and tourism.
Without it, it is unlikely that these activities would be possible. However, the
groundwater is generally unsuitable for irrigation because of its high sodium content,
which makes it chemically incompatible with the soil.
Overlying parts of the GAB are large alluvial fan aquifers of Tertiary age associated
with the major rivers, the Macquarie, Gwydir, Namoi, Border and Condamine.
Increased attention is being given to the integrated management of the Basin's land and
water resources by all of the responsible governments.
The Great Artesian Basin Consultative Council has been establised to coordinate the
sustainable management of the groundwater resources
One of the first tasks of Council was to develop a 'Basin-wide' Strategic Management Plan
which represented a combination of views and needs from across the Basin, and which would
provide a comprehensive enough framework within which Commonwealth, State and Northern
Territory jurisdictions could manage Basin resources.
In September 2000, this was achieved and the Great Artesian Basin Strategic Management
Plan [PDF, 1273kB] was released.
The Murray Groundwater Basin
The Murray Basin, covering some 297,000 km2 is located in the southern part of the MDB
and almost entirely within its boundaries (Brown 1989; Evans et al. 1990) (Figure 1).
It is a relatively thin saucer-shaped basin, between 200 and 600 m thick, consisting of
Cainozoic age unconsolidated sediments and sedimentary rocks, primarily silts, clays and
limestones.
The only outlets are by way of the Murray and to the surface. The basin has limited
storage capacity and the sediments are largely saturated. The thin and flat nature of
the basin means that it can fill quite rapidly, and there is evidence that it has
refilled six or seven times over the past 500,000 years. While previous fillings took
2,000 to 3,000 years, the current one is taking less than one hundred years, due
essentially to the clearing of natural vegetation and its replacement by shallow-rooted
plants, both in dryland and irrigated farming areas. Studies have indicated significant
rises in groundwater levels over the last 25 years.
There are large recoverable reserves of groundwater available in the Murray Basin aquifers,
greater than was earlier believed, but at present, use is a very small percentage of the
sustainable yield. A major reason is that water quality is highly variable.
Of the shallow groundwaters, the best quality water is found around the Basin's margins,
especially in the east and south-east and the south-west, in the South Australian Mallee.
In other areas, especially adjacent to the course of the River Murray downstream of the
confluence with the Murrumbidgee, the groundwaters are highly saline.
Increased use of the groundwaters would contribute to the lowering of the watertables
or at least help to alleviate the continuing rise
Groundwater Use
The State of the Environment Report found that there was a 90% increase in groundwater use
across Australia between 1985 and 1996-97, to about 5000 GL/year.
Overall, 32% of groundwater extracted is for urban-industrial use, 51% for irrigation and
17% for stock watering and rural use.
South Australia, New South Wales and Victoria use more than 60% of groundwater for
irrigation, while Western Australia uses 72% for urban and industrial purposes.
Up to four million people in Australia depend totally or partially on groundwater for
domestic water supplies.
The total volume of drinking quality groundwater (i.e. with less than 1500 mg/L Total
Dissolved Solids) that can be sustainably extracted is estimated to be about 21 000 GL/year.
However, many undeveloped groundwater resources are in remote areas. More importantly,
most estimates of groundwater sustainable yields do not consider the impact of groundwater
extraction on baseflows in rivers, streams, lakes and wetlands.
Little is known about groundwater-dependent ecosystems (e.g. caves and aquifers) and their
water requirements, although many contain unique or endemic species. Many land and water
ecosystems depend on groundwater for at least some of the time, but the interactions
between groundwater and these systems are poorly understood.
In comparison with surface water, there is relatively little information on groundwater
levels, use and quality and increased information is required if groundwater systems are
to be managed sustainably.
Some groundwater resources are already overdeveloped, as the rate of extraction exceeds
the rate of recharge (i.e. groundwater mining). These include the Great Artesian Basin,
many small aquifers in the Murray-Darling Basin, the Perth Basin and aquifers along the
east coast of Australia.
Although the National Water Reforms Framework include provisions for groundwater, groundwater
reform is lagging behind surface water reform in most states and territories.
About 21% of water used in Australia is derived from grounwater sources, but it varies
by State.
Approximately 73% of the water used in Australia (~24 000 GL) is supplied by rivers
and 9% by harvest of overland flows.
Surface water predominates in all States and Territories except Western Australia and
the Northern Territory.
Australia’s mean annual water use (GL) by primary water source (1996/97).
Total surface water (GL) Total groundwater (GL) Ratio surface water/ groundwater use
––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––
New South Wales 9 000 1 008 9.0
Victoria 5 166 622 8.3
Queensland 2 969 1 622 1.8
Western Australia 658 1 138 0.6
South Australia 746 419 1.8
Tasmania 451 20 22.6
Northern Territory 51 128 0.4
ACT 68 5 13.6
––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––
Total 19 109 4 962 3.9
––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––
Groundwater use
Groundwater use across Australia’s States and Territories has increased 58% from 2600 GL
to 4200 GL since 1983/84. In percentage terms, in some States, the increase in groundwater
use is much higher-being about 200% for New South Wales, Victoria and Western Australia.
In volume terms, Western Australia increased groundwater use by almost 800 GL followed by
New South Wales with a 690 GL increase.
Groundwater use information is very limited in availability and reliability.
A reliable estimate of groundwater use cannot be determined relative to the total
groundwater allocated. Only 14% of groundwater management units have some or all water
use metered. Some level of detail on water use is available for 286 or 56% of Australia’s
groundwater management units.
Despite the lack of objective information, water resource managers generally contend
that use far exceeds licenced allocation.
Mean annual groundwater use (GL) by summary (Level 1) use categories.
Irrigation Urban/ Industrial Rural In situ Total
––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––
New South Wales 643 160 205 0 1 008
Victoria 431 127 54 10 622
Queensland 816 265 541 0 1 622
Western Australia 280 821 37 0 1 138
South Australia 354 23 42 24* 419*
Tasmania 9 7 4 0 20
Northern Territory 47 48 33 0 128
ACT 2 0 3 0 5
––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––
Total 2 582 1 451 919 34 4 962
––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––––
* South Australia in situ: not an extractive use and therefore not included
in total water use figure.