Jeff Austin
Countries accessing water in arid areas could learn from the lessons from the co-operative efforts of the wide range of stakeholders that make up the Great Artesian Basin Co-ordinating Committee (GABCC). The GABCC was set up to address the staggering drop in water pressure across the Great Artesian Basin (GAB) and waste of up to 95 per cent of the water brought to the surface. These staggering losses are brought about by free flowing waters subjected to 2 metre annual evaporation rates and seepage in a climate that experiences disastrous repetitive drought and rainfall of around only 450 mm.
The GAB water varies considerably across its coverage of 22 per cent of Australia with water discharging to the surface releasing salt and greenhouse gases (GHG) at a wide range of temperatures and pressures.These waters reaching the surface open up the arid landscape to feral pigs, goats and weeds, and delude our native animals into thinking they can survive during extended periods of drought.
Since the first bore was drilled in 1878 the GAB has been the only reliable source of fresh water for domestic, pastoral, mining, tourism and all other human activity, as well as water dependent ecosystems in much of the arid and semi-arid landscape overlaying the Basin.
By the mid-1990s more than 3,000 bores continued to flow freely into more than 34,000 kilometres of open bore drains. These flowing bores caused a significant drop in the pressure across much of the GAB resulting in more than 1,000 natural springs and associated groundwater dependent ecosystems being lost, and approximately one-third of the original artesian bores ceasing to flow.
GAB waters contribute to the environment an estimated:
• 330,000 tonnes of GHG emissions each year;
• 200,000 tonnes of salt each year, largely onto the Murray Darling Basin; and
• 390,000 mega litres of potable water wasted each year.
As a key driver for the implementation of the Strategic Management Plan, the Australian Government initiated a fifteen-year, AUD450 million, investment package called the Great Artesian Basin Sustainability Initiative (GABSI). GABSI is saving water and stabilising or increasing pressures, which also help to sustain mound springs and their biodiversity.
Nearly two thirds of the way through the GABSI funding period, the statistics include:
• 1,124 bores controlled
• 18,756 km of bore drains removed
• 18,540 km of piping installed
• 293 gigalitres water saved per annum
Towns and communities in remote locations from surface flows are sustained by the GAB as the only reliable source of water which supports stock and domestic usage.
The community is concerned with a projected 40,000 holes to be drilled into the GAB – and with information that cementing them off will not be effective long term. ‘Cementing and completion practices (…) are the main risks to the down hole environment. Many factors can cause the cement to deteriorate. As a result, sufficient zonal isolation cannot be guaranteed for an infinite amount of time.’
Near Chinchilla in Queensland, a previously functioning stock and domestic bore is reported to be constantly rumbling and growling and spurting with gas, and every five minutes or so it erupts into a geyser of gas, which shoots into the air. The aquifer has apparently been fractured at some depth and is venting methane into the atmosphere. In this case, the flow has dropped to a fifth of its previous flow since gas wells were drilled nearby. The community is concerned about inter-aquifer leakage.
So, no matter what country you are in, if you are drilling for water:
• Insist on an appropriate bore construction standard that addresses the possibility of inter-aquifer leakage;
• Do not allow unfettered exploration bores for gas/oil interfering with potable underground aquifers.
About the Author: Jeff Austin is a Civil Engineer recently retired from the GABCC after 10 years as Chairman. During this period he was also a Director on the Namoi Catchment Management Authority. He was awarded an Order of Australia for ‘Water Conservation and Management and the Community’ in 2010. – Outreach Magazine
