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30 per cent of Australia’s consumptive use — and more
than double this in Western Australia. But as surface water
supplies run critically low during drought, groundwater
use increases significantly.
While groundwater has vast potential and is recognized
as a major strategic asset, nobody has a clear idea of its
exact size, how much recharge is occurring or how long it
takes to recharge. The timescales involved in both recharge
and groundwater flow can be extremely long, stretching
over hundreds of years to hundreds of thousands of years.
For Australia’s desert and arid regions, underground
resources such as the Great Artesian Basin (GAB) provide
the only reliable source of fresh water. GAB is one of
the largest and deepest artesian basins in the world and
stretches over 1.7 million square kilometres. But as the
demand for water grows, the worry is that drawdowns on
GAB and other essential water resources across Australia
may be irreversible.
To help inform sustainable planning and management,
the Australian Government directed CSIRO to undertake
robust scientific estimates of current and future water use
in most of the country’s major water systems. Between
2007 and 2010 sustainable yields projects were conducted
in four key regions: the Murray-Darling basin, northern
Australia, Tasmania and south-west Western Australia.
CSIRO scientists examined the likely changes to surface
and groundwater availability during climate change, includ-
ing various drying and wetting climate scenarios. It was a
comprehensive scientific assessment of water yields and
provided an important analytical framework for national
water policy decisions.
Various other important initiatives have been instigated
over the past decade, including the national Groundwater
Action Plan to help explore knowledge gaps through
extensive hydrogeological investigations, and groundwa-
ter capacity-building through the establishment of the
NCGRT. The development of national modelling guidelines
was another key part of a coordinated effort to help better
understand our groundwater systems.
It is no coincidence that all these initiatives were put into
place during the brutal millennium drought. This was a time
when floodplains dried and cracked and farmers watched
their land transformed into dustbowls. The Murray-Darling
basin dropped to just 25 per cent of capacity, placing huge
stress on ecosystems and killing entire forests.
Major cities faced the unthinkable prospect of water
supplies running out. This prompted massive capital
investment in large-scale desalination plants around the
nation — plants that were soon idle as the drought broke
to be replaced by floods.
As the crisis eased so did the urgency for greater
knowledge and more effective management systems for
sustainable water use in future droughts. Policy impera-
tives and funding mirrored the peaks, ebbs and flows of
our extreme weather.
The National Water Commission, established during the
millennium drought, closed in December 2014. But that same
summer more than 150 long-standing weather records were
broken across Australia with new higher temperatures and
longer dry spells. There is clearly no room for complacency
in Australia if we are to protect our water resources and resist
further desertification.
Managing the Murray-Darling basin
The Murray-Darling basin is the agricultural jewel in Australia’s vast,
mostly nutrient-poor land mass. Stretching over 1.06 million square
kilometres — 14 per cent of Australia — it delivers 40 per cent of the
nation’s total agricultural value worth about $A15 billion a year.
While it covers a wide range of climatic and natural environments,
most of the basin is classified as arid or semi-arid. Since the 1900s
extraction and diversion of water has fuelled industrial growth, but
at a cost. Considerable pressure has been placed on the natural
environment resulting in a deterioration in the health of the river
system. As such, it is extremely vulnerable to climate change.
As concern over its future mounted at the height of the millennium
drought, CSIRO was commissioned to oversee the largest ever
technical study of the basin. The 2007/08 Murray-Darling Basin
Sustainable Yields Project found that total flow at the Murray mouth
had been reduced by 61 per cent, causing it to cease flowing into the
sea 40 per cent of the time, compared to just 1 per cent before water
resource development. Heavy groundwater use in the basin was also
found to be unsustainable in seven out of 20 irrigated areas.
The Murray-Darling Basin Authority set out to address these
concerns in its historic national basin plan which was signed into
law in 2012. The plan aims to return a minimum 2,750 gigalitres a
year back to the river system and for the first time introduces a limit
on groundwater use across the basin with consistent management
arrangements for all groundwater resources.
Total groundwater sustainable diversion limits have been set at
3,334 gigalitres a year, which includes a potential 984-gigalitre
increase in the annual extraction limit from areas with relatively low
levels of development.
Image: istock.com/muchemistry
There is no room for complacency if Australia is to protect its water
resources and resist further desertification
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