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Areas where topography prevents the outflow of water are called closed basins. Is the GAB a closed basin? What if external bodies of water flowed in? Is that still "closed"?

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In the far north of the Great Artesian Basin, there is groundwater outflow to the Gulf of Carpentaria. Everywhere else the aquifer behaves as a closed basin with outflow in the form of vertical seepage (e.g. to the Mound Springs of South Australia), artesian overflowing boreholes, and pumped boreholes. There may once have been hydraulic connection to the Southern Ocean, but that ceased several millions of years ago - not such a long time when one considers that the longest through-flow time of groundwater, from east to west, is about two million years.

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  • $\begingroup$ Appreciate! According to your answer, the GAB as a whole is not a closed basin. Is there a maximum sub-region of GAB that only has vertical hydrologic exchange? I want to know a maximum region that the boundary has no lateral hydrologic exchange. $\endgroup$ – StonerYancy Oct 8 '15 at 7:38
  • $\begingroup$ Not quite sure what you mean. All of the GAB has a lateral component in the form of lateral inflow from the recharge zone on the eastern boundary. Do you mean 'how much of the perimeter is effectively impervious'? $\endgroup$ – Gordon Stanger Oct 9 '15 at 9:38
  • $\begingroup$ Actually I got confused about the definition of "closed basin" or "endorheic basin". Sorry about that. $\endgroup$ – StonerYancy Oct 10 '15 at 1:25
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    $\begingroup$ @GordonStanger what is the distinction between "Intake Area" and the GAB in that map? $\endgroup$ – Aabaakawad Oct 25 '15 at 22:18
  • $\begingroup$ I take intake area to be that plan area where recharge exceeds discharge. $\endgroup$ – Gordon Stanger Apr 4 '16 at 19:13
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Most of the underlying strata beneath the Gulf of Carpentaria seabed is part of the Great Artesian Basin (GAB). It extends out to the Arafura Seabed and west of the Torres Strait islands. It may even extend or connect with paleochannels of Papua New Guinea's (PNG's) coastal areas. Geoscience Australia has maps showing the northern borderline or "country" maritime border areas of GAB. One could assume that GAB probably goes all the way to the PNG coastline. CSIRO and Geoscience do not provide maps detailing the geology under the Arafura Seabed or Torres Strait seabed close to the PNG coastline.

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