The Galilee Basin is a semi-arid region, with flora and fauna relying on the ebb and flow of the natural watercourses and ancient springs.
Graziers and other landholders in the region are similarly dependent on groundwater, particularly as surface water in the area – from rivers and creeks – is amongst the most variable in the world1.
Coal mining is a water intensive industry and can impact the integrity of aquifers.
Estimates put the amount of groundwater to be taken by the coal mines proposed for the Galilee Basin at up to 2007 billion litres2. The four mines that already have approval – Alpha, Carmichael, Galilee (China First) and Kevin’s Corner – will take up to 1,770 gigalitres. By way of context, that’s over three and a half Sydney Harbours3.
Water drawdown, contamination and subsidence
Both underground and open-cut mining can impact surrounding waterways and alluvial aquifers. Contaminated water and waste material from coal mines can pose a threat to surrounding land and water.
Underground mining requires “dewatering” of coal seams, which changes groundwater dynamics. Dewatering is the removal of underground water from coal seams, which are themselves aquifers. This process changes the pressure in surrounding aquifers, and groundwater is drawn to the voids created by mining, causing drawdown of the water table in nearby areas.
Dewatering by mines in the Galilee Basin poses potential impacts on the integrity of the Great Artesian Basin, which in a vital groundwater resource for towns and agriculture throughout arid and semi-arid parts of Queensland, New South Wales, South Australia and the Northern Territory4.
Even those of us who know a bit about the Great Artesian Basin don’t know that much: we honestly don’t know how much water can be extracted in one place without having a negative effect in others – Adam Kerezsy, aquatic ecologist. Read more.
One example of contamination as a result of mining operations is acid mine drainage. Acid mine drainage is the oxidation of sulphides in water following mining, leading to the release of pollutants which can contaminate ground water, soil, plants and animals. The drainage can come when polluted water from waste rock, tailings, underground workings and pit walls seeps into the surrounding environment.
A report published by the federal Department of Environment describes acid mine drainage as “a potentially severe source of pollution from mine sites”.
Acid mine and acid rock drainage can cause major long-term environmental problems at many types of mine sites if appropriate management strategies are not adopted. Read the report here.
Subsidence is the sinking or lowering of the land surface. Subsidence can crack waterways which can result in a loss of surface flow, reduced water levels, loss of connectivity between water bodies, decreased water quality, and increased growth of iron-oxidising bacteria (rusty-coloured water bodies) resulting in degradation or loss of aquatic habitats.
Subsidence, or the lowering of the land surface is an unavoidable consequence of any mining method that extracts large proportions of the coal resource, such as longwall mining. Read more.
Water resources are now considered a matter of national environmental significance and are subject to federal government legislation5. This federal legislative oversight comes from an amendment to Australia’s national environment law, known as the ‘water trigger‘, introduced in June 2013. The ‘water trigger’ means the water impacts of proposed large coal mining developments — like some of those planned for development in the Galilee Basin — can be assessed at a federal level during the planning and approval process.
- Groundwater report: Analysis of the cumulative impact of proposed Galilee Basin coal mines on water resources
- Desert Uplands: Information about the region that covers 75,000 square kilometres of outback Queensland
- Desert Uplands bioregion: Mapping and information on biodiversity, water and land use in the Central Queensland region
- Acid Mine Drainage: Background on the issue of pollution from acid mine drainage
- Acid mine drainage in Australia — Its extent and potential future liability: A report from the federal Environment Department
- Mining and the environment: A briefing paper from the NSW Parliamentary Library Research Service
- Queensland risk running the well dry by gifting water to coal, The Conversation, 1 December 2014