Far from bore-ing: What is groundwater?
10 May 2016
Over time, water from rain and rivers migrates through the ground and is stored in porous soils and rocks forming aquifers—which we refer to as groundwater.
Across Australia, vast quantities of groundwater fill the spaces between grains of soil or rock, and flows slowly. In fact, an aquifer is more like a sponge than an underground river. Aquifers often connect with rivers, streams, lakes and wetlands, and groundwater can also sustain 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 per cent of Australia, and containing water that last fell as rain more than one million years ago.
The groundwater cycle
Why is groundwater important?
Groundwater makes up 98 per cent of the fresh water on the planet. It currently makes up around a third of Australia’s water consumption, although this varies from location to location. In the Northern Territory, 90 per cent of water is sourced from aquifers. Across the nation, the highest 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—many townships, farms and mines are totally reliant on groundwater. Farmers sink bores that allow groundwater to flow to the surface from artesian basins, and use modern pumps or windmills to extract water from non-artesian aquifers. In irrigation areas, vast quantities of bore water supply thousands of hectares of crops and pastures. Even large cities are dependent on groundwater—for example, about 70 per cent of Perth's water comes from groundwater (National Water Account 2014).
In many places, groundwater discharges naturally to the surface, bubbling into natural springs or contributing to wetlands. Groundwater often plays a crucial role in sustaining rivers and streams, particularly during droughts. Many ecosystems, including some of our most iconic, depend on groundwater—such as the River Murray and Great Artesian Basin mound springs.
A mound spring on the Oodnadatta Track, South Australia, which is dependent on groundwater (Source: Luke Doherty)
Insight into groundwater
The Bureau provides a suite of groundwater information products. This includes web mapping portals that let you zoom in and explore nationally consistent groundwater information and data for your area.
The newest of these portals is the Australian Groundwater Insight, which is mobile-friendly. Designed for non-experts, anyone can explore hydrogeological information alongside information about licences, bore density, management areas and groundwater trends.
For example, a farmer could look at groundwater levels over the past 5, 10 and 20 years to see if the trends nearby are rising, stable or declining. They can also view groundwater level status, to see if the bores in their area have above or below-average levels. This information can be combined with their entitlements to influence how they might use groundwater on their farm.
If the farmer decides to drill a bore, they could then use the Australian Groundwater Explorer to get specific information from nearby bores—looking at actual water levels and salinity, the drilled depth, and bore logs nearby their property. This will help inform what materials they might be drilling through (such as sand or clay) and which aquifer they should target.
Diagram from the Bureau's Groundwater Explorer showing information on:
a) construction - bore and screened interval depth; and
b) lithology - depth and type of sediments drilled through.
More information: www.bom.gov.au/water/groundwater