Water resources in karst and quarrying impacts

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Water resources in karst and quarrying impacts

• Prof. David Gillieson
• Earth Environmental Sciences
• James Cook University
• Cairns, Australia

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Outline of talk

• Karst hydrological zones and the epikarst
• Limestone mining for cement
• Quarrying impacts and rehabilitation
• Expect the unexpected!

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Zonation of karst aquifers
Diagram by Ken Grimes, Regolith Mapping P/L
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Porosity types and karst aquifer properties
Gillieson D 1996 Caves Processes, Development,
Management, Blackwells
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Karst is a triple porosity aquifer!
fissures 10s of metres/day
pore spaces mm/day
conduits 100s of metres/day
Clearwater Cave, Sarawak 135km long
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Epikarst- the karst engine house

• Close relations between
• vegetation
• soils
• microbiota
• epikarst fissures
• solution processes
• and drainage

Gillieson D 1996 Caves Processes, Development,
Management, Blackwells
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Epikarst depth zonation
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Epikarst storage and transmission

• The epikarst or subcutaneous zone is located at
  the top of the aerated or vadose zone
• From the epikarst, water percolates downwards
  and delivers slow recharge to the phreatic zone
• Epikarst storage can buffer the effects of
  rainfall events on water percolation

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Karst groundwater

• fragility of karst environments evidenced by
  karst groundwater systems
• extremely important water supplies - about 25 of
  the global population is supplied largely or
  entirely by karst waters
• but whose quality is VERY susceptible to
  degradation

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What goes down, must come up...

• rapid transport of pollutants in cave conduits
• main problems are turbidity and sewage
• also herbicides (Atrazine) and pesticides
  (Metamidophos)

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Mining and quarrying

• Limestone widely used for building stone, cement
  manufacture, agricultural lime, industrial flux
  and toothpaste
• Caves may be totally quarried away
• Local pollution of groundwater
• Rehabilitation costly and slow

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Mining for cement

• Top graph is change in use
• Lower graph is volume of limestone quarried for
  cement

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Limestone quarry rehabilitationBenders Quarry,
Lune River, Tasmania

• Quarry operating in World Heritage Area for 40
  years
• Operations affecting WH values, especially in
  large cave underlying quarry
• Commonwealth closed quarry and funded
  rehabilitation and monitoring
• Joint project with Tasmanian Parks Wildlife
  Service

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Exit CaveTasmanian WHA

• Cave is 25km long with extensive glowworm
  colonies and other rare invertebrates
• Extensive dye tracing using Rhodamine WT
• Proved connection between quarry drainage and
  Eastern Passage of Exit Cave
• Monitoring sites established with water quality
  probes and dataloggers

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Quarrying impacts at Lune River, Tasmanian World
Heritage Area

• Removal of cave passages and destruction of
  palaeokarst fills by quarrying
• Increased sedimentation of fine clays in caves
  underlying the quarry
• Recurrent turbidity in Eastern Passage and Exit
  Cave Creek
• Changes in pH, conductivity and sulphate ion
  concentrations in passages draining the quarry
• Re-solution of stalactites by acidified drainage
  waters
• Reduced densities of indicator species of
  hydrobiid snails (Fluvidona spec. nov.) in
  passages draining the quarry
• Gillieson Houshold, 2000. In Drew Hotzl eds.
  Karst Hydrogeology Human Activities, Balkema

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Dissolved sulphate (ppm) at Benders Quarry, Lune
River, Tasmania
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Rehabilitation strategy

• Restore the hydrology of the site by simulating
  the drainage characteristics of the unimpacted
  karst
• Reduce peak runoff by the creation of small
  internal drainage basins which simulate dolines
• Control sediment movement at source by the use of
  control structures and filters
• Establish a stable vegetation cover, preferably
  of perennial plants
• Reactivate the soil biology
• Monitor progress above and below ground

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Quarry rehabilitation strategy
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Detail of drainage control
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Expect the unexpected in karst!

• "Nature to be commanded must be obeyed", Francis
  Bacon, Lord Chancellor of England, ('Essays'
  1620)
• Karst surface and subsurface systems are
  integrated and this renders karst especially
  susceptible to human impacts
• Epikarst is of fundamental importance in the
  control of recharge. It stores and mixes water
  and redistributes recharge - and any pollution
• Conventional groundwater models should not be
  applied to karst for management purposes, because
  karst aquifers have triple porosity
  characteristics
• Best place to monitor the condition of karst is
  at the outflow spring, because spring outflows
  integrate the effects of all upstream activities