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Borewater in the balance
Flinders University of South Australia
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The declining level of water in Adelaide’s bores is a telling sign that water is not being recharged to them at a rate that is keeping up with discharge through natural losses to the coastline from aquifers, or from extraction from groundwater bores.
And, according to Flinders University hydrogeologist Professor Craig Simmons, it is further evidence that the time has come to seriously consider the rates of sustainable borewater use and our attitude towards groundwater.
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Flinders University hydrogeologist Professor Craig Simmons |
"In response to surface water restrictions, the number of bores is reaching an unprecedented level," he said.
"The current belief is that the backyard bore phenomenon is rampant."
Professor Simmons is a member of the National Groundwater Reform Group, a national network of leading groundwater scientists and specialists who are calling for action to conserve groundwater through improved regulation and management.
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Professor Simmons said that the present lack of restrictions on domestic groundwater use reinforces the false premise that groundwater is an inexhaustible resource. Armed with the knowledge that aquifer levels are declining means that we need to think seriously about what the growth in the number of groundwater bores and uncontrolled groundwater use might eventually mean for our aquifers and other water resources
"All the restrictions on tap-water with absolutely no discussion on groundwater sends the message that one is limited and that the other is infinite and indefinitely available, and this is just not the case," he said.
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Professor Simmons said water conservation needs to be tackled holistically, and that the conservation of surface water and groundwater should not be treated as separate issues because the two are intimately connected. Groundwater needs to feature much more prominently in our water debates and in discussions on water restrictions. It continues to be a case of "robbing Peter to pay Paul".
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"We need policies and water management frameworks that see these things as part of an integrated water cycle. Currently, if you have a bore, you can water all day, every day and there is nothing to penalise you, whereas improper use of tap-water for watering the garden brings warnings and fines."
With only a comparatively modest capital cost required to sink a bore and fit a pump, Professor Simmons believes that cheapness is driving a lack of respect for bore water. If we restrict the use of surface water through restrictions, but do not consider groundwater in any urban water restriction framework, it is natural that the use of groundwater is going to increase. We have seen that this is in fact already happening as a result of current water restrictions.
"I think there is a case for groundwater to be subject to some form of restriction like surface water, and to treat these resources a little more equally. At the very least, there needs to be an urgent discussion on the role of groundwater in domestic water use and its notable absence in current water restriction strategies" he said.
Professor Simmons said that in a bid to quantify urban usage, it is a problem when we do not know how many unlicensed domestic bores exist and how much water is being extracted from the aquifers.
"These aquifers, like rivers, are responding to rainfall and that is how they are recharged - if you have an extended drought, aquifer levels will fall as well. The current hypothesis is that Adelaide’s aquifers are recharged from rainfall in the Mount Lofty Ranges, but we do not yet have a firm grip on the recharge rates. The water we pull out of a bore today may have been recharged hundreds or thousands of years ago. It is old water."
But even without base level statistics on inputs and outputs to the aquifer, Professor Simmons said the measurements provided by bore hydrographs send a clear message.
"It is like a bank account where the amount of the deposits and withdrawals are not known, but we can see the balance. While we may not know the extraction or the recharge rates, we have the firm irrefutable evidence that the water levels in many aquifers are falling, and that is a matter for serious public concern."
More Info:
Flinders University of South Australia |
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