Groundwater is water that is located below the earth's surface. Over time, water from rain and rivers migrates through the ground and is stored in porous soils and rocks. The study of groundwater is known as hydrogeology.
Groundwater is found in vast quantities filling the spaces between grains of soil or rock; it slowly flows through aquifers; it connects with rivers, streams, lakes and wetlands; it feeds trees and vegetation. Australia is a very old continent, and much of its groundwater is tens of thousands, even hundreds of thousands of years old.
For example, the Great Artesian Basin in central Australia is the largest aquifer of its kind in the world, covering 22% of Australia, and containing water that is more than a million years old.
Groundwater makes up 98% of the fresh water on the planet. It currently makes up around a third of our total water consumption, although this varies from location to location. In the Northern Territory, 90% of water is sourced from aquifers, while the highest concentration of groundwater use is in the Murray–Darling Basin.
In many regions of Australia, particularly in the outback, groundwater is the only available source of water – numerous townships, farms and mines are totally reliant on groundwater. Farmers sink bores to bring water to the surface from artesian basins, and windmills use wind energy to pump water from hidden aquifers. In irrigation areas, vast quantities of bore water supplies thousands of hectares of crops and pastures. Even large cities are dependent on groundwater; for example, about 70% of Perth's water comes from the Gnangara Mound.
In many places, groundwater discharges naturally to the surface, bubbling into natural springs or contributing to rivers and wetlands. Groundwater often plays a crucial role in sustaining rivers and streams, particularly during droughts when it becomes a valuable buffer. Many ecosystems, including some of our most iconic, depend on groundwater.
In Australia, the importance of groundwater is pronounced given that Australia is the driest inhabited continent on Earth and surface-water resources are limited over vast areas.
Groundwater is a finite resource, and aquifers can become depleted when extraction rates exceed replenishment, or ‘recharge’, rates. Like surface water, groundwater can become polluted or contaminated.
Despite its importance, groundwater is poorly understood and often undervalued. This may in part derive from the nature of groundwater: a complex, hidden resource that is difficult to conceptualise. It is for this reason that the NCGRT is working hard to learn more about groundwater.
If you too would like to learn more about groundwater, we recommend the National Water Commission’s Groundwater Essentials booklet and our own NCGRT publication Groundwater in Australia.