Non-renewable groundwater resources: a ... - unesdoc - Unesco

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NON-RENEWABLE GROUNDWATER RESOURCESThe Great Artesian Basin, AustraliaM.A. HabermehlIntroductionThe Great Artesian Basin, underlying 1.7 million km 2 of semi-arid regions of Australia, is one ofthe larger artesian basins in the world. It is Australia's largest and most important groundwaterresource (Habermehl, 2001). This confined basin is up to 3,000 m thick. It includes parts of theStates of Queensland, New South Wales, South Australia and the Northern Territory (Figure 1).The mining of the artesian pressures and groundwater in storage during the last 125 years hasaffected the Basin to varying degrees. It has produced large-scale drawdowns and reduceddischarges from flowing artesian water boreholes and springs. Flowing waters from boreholesare important for the pastoral industry in the Basin and flowing waters from springs are essentialfor the maintenance of their ecosystems.Recent programs aim to rehabilitate water boreholes in poor condition, equip boreholeswith control valves, and replace with polyethylene piping systems the inefficient open earthdrain distribution systems that cause up to 95 percent wastage of the water. These measures willbenefit groundwater and rangeland management and assist to alleviate land degradation andplant and animal pest problems. A reduction of the uncontrolled discharges, a halt in thediminution of the artesian pressures and a partial recovery of the artesian pressures are beingachieved. A Strategic Management Plan for the whole of the Basin was developed by the GreatArtesian Basin Consultative Council in 2000. It addresses basin-wide management issues, sustainabledevelopment and use of artesian groundwater.Development82Groundwater in the Great Artesian Basin has been exploited from flowing artesian waterboressince artesian water was discovered in 1878, allowing an important pastoral industry to beestablished. Waterbores are up to 2,000 m deep, but average about 500 m. Artesian flows fromindividual bores exceed 10 x 10 6 L/day (more than 100 L/s), but the majority have much smallerflows. About 3,100 of the 4,700 flowing artesian waterbores drilled in the Basin remain flowing.The accumulated discharge of these waterbores (including water supply bores in about70 towns, as in most cases the artesian groundwater supply is the only source of water) is about1,200 million L/day, compared to the maximum flow rate of about 2,000 million L/day fromabout 1,500 flowing artesian waterbores around 1918 (Figure 2).Non flowing artesian waterbores, which number about 20,000, are generally shallow i.e.several tens to hundreds of metres deep. It is estimated that these generally windmill operatedpumped waterbores supply on average 0.01 million L/day per borehole, and produce a totalof about 300 million L/day. High initial flow rates and pressures of artesian waterbores havediminished as a result of the release of water from elastic storage in the groundwater reservoir,
CHAPTER 5 ■ REGIONAL CASESFigure 1Hydrogeological sketch map of Great Artesian Basin of Australia83
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From the World BankThe World Bank,
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ContentsChapter 1Concept and import
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NON-RENEWABLE GROUNDWATER RESOURCES
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