24
STANLEY N. DAVIS
Fig. 12. Great Artesian Basin in eastern Australia. Arrows show only approximate
direction of groundwater movement. Heavy lines show border of artesian basin.
Shallow, generally unconfined, aquifers are present along watercourses
in the eastern part of the basin. Also, in the northeast, Permian sandstones
below the primary artesian aquifers are probably water bearing. The cover
of Cretaceous clay is absent along the southern margin of the basin where
water is only semiconfined and has lacked a strong original artesian head
(Ward, 1946).
Recharge to the artesian basin is thought to be through the sandstone
outcrops along the eastern margin of the basin. The eastern margin is at
a higher elevation and receives more precipitation than the rest of the
basin, although under present climatic conditions little excess water is
available for recharge. The main sandstone aquifers generally pinch out
in the subsurface before reaching the western margin of the basin. Also,
the western margin of the basin is arid, so little recharge from this direction
is thought to have taken place during the past few thousand years.
Many questions exist concerning the natural discharge of the artesian
system. The famous mound springs in the southern and northcentral parts
of the basin may represent areas of upward leakage along fractures in the
confining beds of the system. The mounds are generally 1-10 meters high
and are made of travertine deposited by the artesian water. Discharge may
also occur into the Gulf of Carpentaria in the northern extremity of the
basin. The water in much of the Carpentaria Subbasin is brackish to saline
(Whitehouse, 1945) suggesting that, if there is active discharge, it is sluggish. Natural discharge also occurs along the eastern margins of the basin
where deeper valleys cut into the permeable intake beds.
The first deep wells were drilled in the basin during the late 19th century.
STANLEY N. DAVIS
Fig. 12. Great Artesian Basin in eastern Australia. Arrows show only approximate
direction of groundwater movement. Heavy lines show border of artesian basin.
Shallow, generally unconfined, aquifers are present along watercourses
in the eastern part of the basin. Also, in the northeast, Permian sandstones
below the primary artesian aquifers are probably water bearing. The cover
of Cretaceous clay is absent along the southern margin of the basin where
water is only semiconfined and has lacked a strong original artesian head
(Ward, 1946).
Recharge to the artesian basin is thought to be through the sandstone
outcrops along the eastern margin of the basin. The eastern margin is at
a higher elevation and receives more precipitation than the rest of the
basin, although under present climatic conditions little excess water is
available for recharge. The main sandstone aquifers generally pinch out
in the subsurface before reaching the western margin of the basin. Also,
the western margin of the basin is arid, so little recharge from this direction
is thought to have taken place during the past few thousand years.
Many questions exist concerning the natural discharge of the artesian
system. The famous mound springs in the southern and northcentral parts
of the basin may represent areas of upward leakage along fractures in the
confining beds of the system. The mounds are generally 1-10 meters high
and are made of travertine deposited by the artesian water. Discharge may
also occur into the Gulf of Carpentaria in the northern extremity of the
basin. The water in much of the Carpentaria Subbasin is brackish to saline
(Whitehouse, 1945) suggesting that, if there is active discharge, it is sluggish. Natural discharge also occurs along the eastern margins of the basin
where deeper valleys cut into the permeable intake beds.
The first deep wells were drilled in the basin during the late 19th century.