The water down under
Box 2 | Our outback oases – groundwater dependent ecosystems
The Great Artesian Basin is not just important for people to survive in the outback. The natural surface or mound springs of the GAB support many distinctive communities of plants and animals.
Mound springs are places where the groundwater has naturally flowed to the surface, with a small mound or hill created due to the build-up of sediments or salts from evaporating water. They vary from a few centimetres to 100 metres in diameter. These springs have been dubbed the 'oases of the outback' and there are hundreds stretched across the Basin, mainly in the south-west.
The mound springs support a variety of plants, aquatic invertebrates and fish – some of which occur nowhere else in the world – that are in danger of becoming extinct because water flows are declining as the pressure in the GAB falls due to over-extraction. Mound springs support a variety of grasses, such as the salt-tolerant samphire and button grass, reeds, green algae and Cyanobacteria.
They are also home to more than 40 species of freshwater snails found nowhere else, some of which are only found in a single spring. Because the springs are on pastoral land, the tiny animals are in danger of being trampled by stock that drink from the spring.
It's probable that some species have already been driven to extinction. Many springs have dried up over the past century due to pastoral bores being drilled and over-extraction of water. Of the springs that remain, it's estimated that some now flow at only 10 to 30 per cent of their former discharge rate.
Apart from these unique species, the mound springs are also an important habitat and source of water for birds and land animals which have few alternative water sources in such arid landscapes. While some native – and introduced – species benefit from introduced bores in arid areas, others adapted to the dry conditions are decreasing in number.
Boxes
Box 1. Using science to measure and manage groundwater
Box 3. Research into sustainable groundwater use
Related sites:
Mound springs in arid Australia (Australian Museum)
Springs (Queensland Government Environment Protection Agency, Australia)
Oases in the desert: Mound springs and their role in desert hydrology (Journal of the Virtual Explorer, 2005)
Groundwater dependent ecosystems (Connected Water, Australia)
The state of Australia's birds 2004 (Australian Government Department of the Environment and Water Resources, Australia)
Posted February 2007.