Management of the karst and groundwater
Prepared by Ken Grimes & Kevin Mott
The management problems of The Gambier Karst
Region fall into three areas:
Water Supply and Quality:
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| Sinkhole with adjoining dairy & yards. Click on
the photo for a larger view (117kb.JPG) |
The Tertiary Limestone forms the major aquifer in the region, and it has
been referred to as one of the best aquifers in Australia. However, it
will be a major job to keep it that way in the face of growing demand,
and the continuing threats of pollution from a variety of sources
There may be a growing problem in maintaining supplies in the
face of increasing demand for both private, agricultural and industrial
usage. Water quality can be compromised by pollution from a variety of
sources: stormwater, sewer and septic drainage in the towns, farm activities
(in particular wastes from the dairies and piggeries), and some major industries
such as those involved in the treatment of mill timbers, paper pulp, cellulose
etc. In the past, abattoirs have been a source of pollution with
some still a cause for concern. Early cheese factories also introduced
major pollution plumes into the aquifer and these are still traveling through
the system.
Of increasing concern is contamination of the groundwater from diffuse
sources such as grazing. Several studies are being undertaken by CSIRO
to look at the effects of this diffuse contamination. In some areas, particularly
in the north of the region, increased salinity from clearance and irrigation
is becoming a greater problem.
Although regulatory controls exist under the Environment Protection
Act these only cover large scale operations. Small scale operations come
under a general duty of care and are usually only scrutinised when there
is a direct complaint. Often a number of small, badly run, operations can
cause more problems than the reasonably run large ones. Unfortunately,
these small operations have more severe budgetary constraints so the owners
are reluctant to upgrade, despite programs of public education.
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The theme of the ACKMA 99
conference symposium will be
Water Below: The management of Karst Aquifers.
(what goes down must come up) |
Surface Karst:
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| Rubbish in a doline in a pine plantation. Click it for
a 122kb.JPG |
The main problems here have to do with introduction of pollutants into
the aquifer via the dolines, cave entrances and "runaway holes". Direct
damage to dolines and cave entrances also occurs from forestry and agricultural
activities. Ripping of limestone for increasing irrigation activity can
disturb karst pavement areas and change the hydrology. Subsequent irrigation
or intensified land usage will also have an impact on water quality from
increased fertiliser applications. Many dolines and entrances have been,
and still are, used as rubbish dumps. There have been major clean-ups of
some dolines and caves, for example: Engelbrecht
Cave in the town of Mount Gambier is now a tourist cave, and Rendelsham
Cave near Millicent has recently been cleaned up and developed as a recreational
area. The stromatolites that grow
in the cenotes may be endangered by water pollution - either directly or
indirectly by the growth of surface algal mats which block the sunlight.
Swimmers in some of the spring ponds have caused damage to the aquatic
vegetation.
Cave Management:
Diver at Piccaninnie Ponds |
Management problems within the caves are mainly related to people access,
and the damage that results therefrom. About a third of the known caves
in South Australia are on crown land (mainly State Forests), I do not have
handy figures for Victoria. The region has four sets of show caves: Several
caves at The Naracoorte Caves, and also Tantanoola Cave, Engelbrecht Cave
in Mount Gambier, and Princess Margaret Rose Cave on the Glenelg River
(see map, below). There are no show caves in the volcanic region, but two
lava caves at Mount Eccles are open to
the general public and access steps have been put into one of these. Cave
(and cenote) diving is a special activity in the Mount Gambier area that
is stringently controlled by a certificate and permit system.
Beneath pine plantations evapotranspiration is much higher than elsewhere
and this can drop the local water table by several metres, drying up pools
and speleothems. A few caves have been intersected by quarries; one of
these became a major fossil bone site - with the quarry operations continuing
beside it.
Tourist Caves in the Gambier Karst Region
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A worry with syngenetic
karst caves, and to a lesser extent with those in the Tertiary Limestones,
is stability. "Soft-rock caves" are not as strong as the typical "hard-rock"
cave of the east coast, and so roof fall is statistically more likely.
Cavers have to be a bit more careful about bumping the roof, and cave managers
should do regular inspections of their tour caves.
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Would you eat your lunch under this roof? Click it (gently!)
for a bigger version (100kb.JPG) |
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Copyright (c) Ken Grimes, 1998: ken-grimes@h140.aone.net.au
URL for this page: http://www.netserv.net.au/cwork/ackma99/grimes/Manage.htm
