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Conjunctive water management is the combined use and
management of groundwater, surface water and additional
sources, such as recycled stormwater and wastewater, to
improve water security and the stability of supply while maintaining
water quality. Conjunctive water management can help to manage
floods and ensure that there is enough water for cities, irrigation
and the environment when drought hits.
Conjunctive water management has several advantages.
First, it augments the natural processes of water storage in the
landscape, avoiding evaporative losses. In the Murray-Darling
Basin, up to 3000 gigalitres (GL or billion litres) of water per year
evaporates from surface water storages.
Second, it helps communities to adjust to climate variability and
uncertainty by channelling and storing floodwaters, providing
additional water reserves during dry periods and enabling irrigators
to continue to receive water during droughts.
Third, it prevents aquifers from being over pumped, and ensures
that they are recharged during wet years, therefore guaranteeing
that rivers continue to receive flows of water from aquifers during
dry times. It can also assist water managers to synchronise
supply with specific consumptive and environmental watering
Fourth, conjunctive water management knowledge and technology
can become a valuable new export industry. By 2025, the United
Nations (UN) estimates that 1.8 billion people will live in regions
where water is scarce, and two-thirds of the world’s population
could be living in conditions in which the supply of clean water
does not meet demand. Australia can help to solve these problems
by supplying technologies, skills and expertise to develop aquifer
storage and recovery solutions.
It is important that conjunctive water management is based
on careful analysis of local hydrology and geology in order to
safeguard water quality, and to ensure that the environment is not
What’s happening? Australia and the world
We are currently already storing approximately 45 gigalitres of
‘natural’ water in aquifers in the Burdekin region of Queensland
every year for use in agriculture and horticulture, at around
$0.11 per kilolitre. A 23-gigalitres-per-year capacity for storing
recycled stormwater underground has been developed at 34
sites around Adelaide, and a 14-gigalitre-capacity plant for
storing highly treated wastewater is in operation in Perth, with
further increases in capacity planned.
In Orange County, California, they store around 300 gigalitres per
year – enough for the annual household use of 2.3 million people.
One water bank in California has held up to 800 gigalitres for its
members. The known capacity of aquifers to store additional water
below Perth, Adelaide and Melbourne could meet the needs of
2.5 million people per year – and may be far larger. Between 1997
and 2014, the Arizona Water Banking Authority stored 4500
gigalitres to ensure future supplies of groundwater.
The argument that there is no spare surface water to store
underground ignores hundreds of gigalitres per year in dam
spills and floodwater, recycled stormwater, and wastewater. This
‘spare’ water can be stored by channelling water to sand or gravel
beds, where it can filter down into the aquifer. When infiltration is
blocked by rock or clay, injection drills can be used.
Storing water underground and extracting it can involve significant
costs, but these need to be balanced against the high engineering
and environmental costs of new dams and reservoirs. Also, surface
storages lose one-third or more per year due to evaporation, and
this cost is rarely acknowledged. If we choose not to make water
users pay the full cost of surface storage, including evaporative
losses, then there is a case for policy to reduce the cost of
aquifer storage for users, especially in areas where new irrigation
development is being considered, such as northern Australia.
Where to from here?
There are many opportunities to benefit from improved conjunctive
water management if political and institutional barriers can
be overcome. A national research study in 2013 showed
that conditions for the implementation of conjunctive water
management have only been partially met by the Australian states.
There has been progress towards integrated groundwater and
surface water accounting and planning, but there is still little
BY 2025, THE UNITED
NATIONS (UN) ESTIMATES
THAT 1.8 BILLION PEOPLE
WILL LIVE IN REGIONS
WHERE WATER IS SCARCE,
AND TWO-THIRDS OF THE
COULD BE LIVING IN
CONDITIONS IN WHICH THE
SUPPLY OF CLEAN WATER
DOES NOT MEET DEMAND.
AUSTRALIA CAN HELP TO
SOLVE THESE PROBLEMS BY
SKILLS AND EXPERTISE TO
DEVELOP AQUIFER STORAGE
AND RECOVERY SOLUTIONS
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