The Great Artesian Basin (GAB) is the largest and deepest groundwater system in the world, covering over 1.7 million square kilometers of inland Australia. This vast underground water resource extends beneath large portions of Queensland, New South Wales, South Australia, and the Northern Territory. The GAB is fundamental to the nation’s inland economy, providing the only reliable source of fresh water across much of the continent’s arid and semi-arid interior. The economic activity supported by this water, particularly for pastoral and agricultural industries, is substantial.
The Geology of the Great Artesian Basin
The GAB’s immense water storage capacity is a result of a unique geological structure formed over millions of years. This structure is composed of alternating layers of porous and impermeable rock, which create a giant subterranean reservoir. The main aquifers are layers of porous sandstone, originally deposited by ancient rivers and lakes during the Triassic, Jurassic, and Cretaceous periods.
These water-bearing layers are trapped beneath younger, non-porous layers of mudstone and siltstone, which act as confining layers or aquitards. Rainwater enters the system at higher elevations, primarily along the western edge of the Great Dividing Range (recharge areas). As the water slowly percolates through the sandstone, the confining layers trap it, causing it to become pressurized. This pressure is what makes the water “artesian,” meaning it can flow naturally to the surface when a bore taps into the aquifer, without the need for mechanical pumping.
Agricultural Reliance in Australia’s Arid Interior
The regions overlying the GAB are characterized by semi-arid or arid climates, where rainfall is low and surface water sources are highly unreliable or entirely absent. This harsh environment means that without a secure water source, large-scale agricultural operations would be impossible across millions of square kilometers of inland Australia. The GAB provides a stable, year-round water supply, transforming otherwise unproductive land into viable grazing and farming country.
Access to this secure groundwater has allowed for the settlement and continued prosperity of rural communities and the establishment of vast cattle and sheep stations. The GAB underpins a significant portion of the Australian economy, supporting the immense inland pastoral industry. The resource guarantees a baseline level of water security, allowing farmers to maintain stock and livelihoods through prolonged drought periods that would otherwise devastate their operations.
Water Utilization for Livestock and Cropping
The primary use of GAB water is for the livestock industry, supporting over 14 million beef cattle and 11 million sheep and lambs across the basin’s regions. The water is accessed through deep bores, which historically fed open channels called bore drains that delivered water to numerous watering points. These systems provide drinking water across immense properties, allowing graziers to utilize land far from natural watercourses.
The water’s natural characteristics influence its suitability for use. GAB water is often naturally hot, with temperatures ranging from 30 to 100 degrees Celsius, and can contain dissolved minerals. The high concentration of dissolved solids or sodium can limit its use for intensive cropping. Farmers use it for cropping, primarily for supplementary irrigation of high-value produce or for growing fodder crops to sustain their livestock during dry spells.
Protecting the GAB for Future Generations of Farmers
The long-term viability of farming in the GAB region depends on the sustainable management of the groundwater resource. Decades of uncontrolled use, where numerous bores flowed freely, led to a significant decline in artesian pressure across the basin. This pressure reduction threatened the flows of many bores and natural springs.
In response, the Great Artesian Basin Sustainability Initiative (GABSI) was established to manage the resource and recover pressure. This program focuses on the Capping and Piping Scheme, which involves rehabilitating uncontrolled bores and replacing wasteful open bore drains with sealed pipe systems and troughs.
The open drains caused significant water loss through evaporation and seepage. The closed piping systems prevent this loss, saving hundreds of gigaliters of water annually and helping to restore artesian pressure in certain areas. By investing in this modern infrastructure, landholders secure a more reliable and efficient water supply, which supports better stock management and ensures the resource remains available for future generations of farmers and the regional communities that rely on them.