Australians
accused of groundwater abuse
By Robinson Shaw
Wednesday, November 24, 1999
As these windmills pump
groundwater from the Earth, CSIRO scientists say
research is needed to better understand how
underground water sources, like fractured rock
aquifers, work. |
Australia is abusing its important
groundwater resources in some regions of the continent
because little is understood about how these water sources
work, warned Dr. Peter Cook, a land and water scientist from
CSIRO, Australia's leading scientific research organization.
"We need to give people the ability
to use groundwater sustainably. In many areas people are
watching the water levels falling and know they are using
too much but it is very hard after the fact to do anything
about it," said Cook. "So as we make more and more
use of this water source, it's vital we quickly gain an
understanding about it and how to manage it."
"In many cases more water is being
extracted than is naturally replenished," says Dr Cook.
Rural water producers and water engineers need to improve
their understanding of water that comes from fractured rock
aquifers, he said.
Groundwater is stored in sediments like
sand, sandstone and gravel where linked porous systems serve
as aquifers. It is also stored in fractures of rocks that
are not porous. Snowfall and rainfall collects in the
fractures between rocks and an aquifer is created.
Fractured rock aquifers are found in fewer
than 40 percent of Australia's land area. They are used
extensively to supply irrigation and domestic water, mainly
in regions where population or agriculture is increasing and
where existing sand aquifers are already fully exploited or
over-exploited.
"Very little is known about fractured
rock aquifers. This means people often use the wrong
management methods, even though they don't work," said
Cook.
Forty percent of Australia's
groundwater comes from fractured rock aquifers and a
lot of that water is used for crop irrigation. |
A key challenge for water managers is to
determine the amount of rainfall needed to recharge or
replenish a fractured rock aquifer. This can vary from one
percent to 30 percent of annual rainfall, depending on the
location, soil type and other environmental factors, said
Cook. They also need to understand how the alignment of the
cracks in the rock affects the water's flow and speed which
will help decide where to drill and to what depth, he said.
"If we don't know how fast the
groundwater moves and the rate at which it recharges, then
no realistic allocation rate can be set for its
extraction."
Understanding the character of rock
fracture can also help reduce groundwater contamination,
because high water speed through fractures can move
contaminants long distances very quickly. Many water
engineers mistakenly believe water storage and transport in
fractured rock aquifers is similar to sand aquifers, which
are less complex and much easier to manage, said Cook.
"As a result there are areas of
Australia where people are using three to four times more
water than is being recharged, so the water is running out.
This highlights the need to develop proper tools to manage
and use groundwater sustainably," he said.
Three CSIRO-led research projects are
pioneering systems to measure the movement and recharge
rates for fractured rock aquifers across Australia. In
Queensland's Atherton Tablelands, where fractured rock
groundwater is used to irrigate horticultural crops during
the dry season, there are concerns that over-extraction may
damage protected rain forest further downstream.
In New South Wales, Wagga Wagga,
scientists have controlled the movement and direction of
water in fractured rock aquifers to maximize efforts in
combating dryland salinity.
In South Australia's premier wine-growing
district, the Clare Valley, growers want to know how much
more water they can use to increase vineyard capacity,
without overexploiting the resource.
Copyright 1999, Environmental News
Network, All Rights Reserved
Related Links:
Visit CSIRO
to learn more about scientific research down under in
Australia.
The United States Geological
Survey provides information on water resources in the
states.
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