Springs fed by the Great Artesian Basin, water that fell as rain 2 million years ago. Endemic species evolved in isolation in these desert oases, found nowhere else on Earth.
A look at deep time
The water bubbling to the surface at the Eulo Artesian Springs began its flow when mammoths still roamed the Earth. This water is emerging from the Great Artesian Basin (GAB), one of the largest and deepest artesian basins in the world. The GAB covers 1.7 million square kilometers, underlying 22% of the Australian continent. The water enters the basin primarily along the western slopes of the Great Dividing Range, seeping into layers of porous sandstone laid down during the Jurassic and Cretaceous periods.
This ancient rainwater then begins an incredibly slow underground migration, moving at a rate of only one to five meters per year. Over vast timescales, it travels westward, deep beneath the surface. In the Eulo region, geological faults and thinning layers of rock allow this pressurized water to escape to the surface, creating the springs. Isotope dating using carbon-14 and chlorine-36 confirms the age of the water in these discharge zones can be up to two million years old. As the water travels, it is heated geothermally, with temperatures across the GAB ranging from 30°C to 100°C.
Islands of evolution
The Eulo Springs are geological curiosities; they are isolated ecological islands in a semi-arid landscape. This isolation has driven the evolution of a unique collection of endemic species—organisms found here and nowhere else on the planet. The constant water supply creates a permanent wetland, different from the surrounding environment, allowing specialized life to develop.
Among the residents are several species of hydrobiid snails, such as those in the Jardinella and Eulodrobia genera, which have diversified in these specific spring complexes. The springs also host endemic crustaceans, including the isopods Ponderella bundoona and P. eromanufactia, and a unique species of amphipod from the Austrochiltonia genus.
The plant life is equally distinct. Several species are GAB endemics, including the grass Eragrostis fenshamii, salt pipewort (Eriocaulon carsonii), and spring milfoil (Myriophyllum artesium). These organisms are entirely dependent on the steady flow and specific water chemistry of the artesian springs for their survival. The entire spring community is federally listed as an endangered ecological community, threatened by factors like water extraction from the GAB, which reduces pressure and flow to the springs.
💡Fun Facts
The water emerging from some springs fell as rain before the existence of modern humans.
The Great Artesian Basin holds an estimated 64,900 cubic kilometers of water, enough to fill Sydney Harbour 130,000 times.
Some of the springs form "mound springs," which are cones of mineral-rich clay transported to the surface by the water over millennia. Some recorded mounds have reached 6 meters in height.
The springs allow some plants, like the carnivorous bladderwort *Utricularia dichotoma*, to flourish hundreds of kilometers away from their typical coastal habitats.
The natural mud springs reserve is accessible year-round. The commercial Eulo Artesian Mud Baths operates on a booking schedule, typically with sessions at 9am, 11am, 2pm, and 4pm.
Admission
Access to the natural Artesian Mud Spring Reserve just outside Eulo is free. The commercial Eulo Mud Baths experience is a paid activity and requires booking.
Accessibility
The terrain around the natural springs can be uneven. The commercial mud baths have facilities with disabled access available upon request.