NDA (II) 2022 General Ability Test · Question 57 of 150

Correct — C, Queensland. The Great Artesian Basin is the largest and deepest artesian groundwater basin in the world, covering roughly 1.7 million square kilometres and underlying about 22 per cent of the Australian continent. It spreads across four jurisdictions — most of Queensland, the northern part of New South Wales, the north-eastern corner of South Australia and the south-eastern corner of the Northern Territory. Queensland holds the major portion by a wide margin, and the basin's water is what makes pastoral grazing possible across large stretches of outback Queensland where surface water is scarce or seasonal.

• (a)Western Australia — The Great Artesian Basin does not extend into Western Australia at all. It lies in the eastern half of the continent; Western Australia is separated from it by the Western Plateau.
• (b)Victoria — Victoria sits in the far south-east and lies outside the basin. The basin's southern reach is northern New South Wales, and it does not cross into Victoria.
• (d)Northern Territory — Only the south-eastern corner of the Northern Territory sits over the basin — a small share compared with Queensland, where most of the state is underlain by it.

An artesian basin is a groundwater store in which a permeable, water-bearing layer such as sandstone is sandwiched between impermeable layers, and the water enters the aquifer at a higher elevation than the point where a bore is sunk. The confined water is therefore under pressure, so when a well is drilled the water rises on its own without pumping. The Great Artesian Basin is the classic textbook example and by far the largest of its kind.

There are two routes to the answer. The direct route is the map — the basin occupies the Central Lowlands of eastern Australia, which is overwhelmingly Queensland territory. The indirect route is the economic association most textbooks make, between artesian bore water and sheep and cattle grazing in the dry interior of Queensland. Either route eliminates Western Australia and Victoria at once, which lie outside the basin altogether.

• The Great Artesian Basin covers about 1.7 million square kilometres and underlies roughly 22 per cent of the Australian continent.
• It is the largest and deepest artesian basin in the world.
• It extends across Queensland, northern New South Wales, north-eastern South Australia and the south-east corner of the Northern Territory, with the major portion in Queensland.
• In an artesian basin the aquifer is confined between impermeable layers, so water rises to the surface under its own pressure when a bore is sunk.

• Choosing Western Australia because it is the largest state — the basin lies in eastern Australia.
• Confusing an artesian basin, which is a groundwater store, with a river basin, which is a surface drainage area.

Usually a one-line world-geography location item, occasionally as a statement set on how artesian water reaches the surface.

• practice — not a real PYQ

  The Great Artesian Basin, the largest artesian groundwater basin in the world, is located in

  • (a)Brazil
  • (b)Australia
  • (c)Canada
  • (d)South Africa

  Answer(b) Australia — it underlies about 22 per cent of the continent, mostly in Queensland.

• practice — not a real PYQ

  In an artesian well, water rises to the surface without pumping because

  • (a)the aquifer is unconfined
  • (b)the water table lies below the bottom of the well
  • (c)water in the confined aquifer is under hydrostatic pressure
  • (d)the surrounding rock is highly permeable

  Answer(c) water in the confined aquifer is under hydrostatic pressure — the recharge zone lies higher than the well mouth.