The ratio of oxygen-18 to oxygen-16 isotopes in ice cores can reveal a lot about the Earth’s climate at any one point and can be cross-referenced with other data such as volcanic ashes to find age. Researchers like Professor Chris Turney, director of Earth and Sustainability Science Research Centre (ESSRC) at UNSW Sydney, are using this data to guess what higher temperatures might mean for rainfall and other weather events in the future. Ice cores, the oldest of which come from Antarctica and go back 800,000 years, tell a story of temperature, precipitation, atmospheric makeup, volcanic activity and even wind patterns. “But the techniques are not as widely used as they might be.” “The biggest change we’ve seen over the last 20 years is that there’s more techniques to date groundwater,” says Professor Peter Cook, a hydrogeology expert at Flinders University. To date water this old, researchers use the well-known carbon-14 method (which has a half-life of 5,730 years – the time it takes for half of the radioisotope present to decay), as well as argon-39 and krypton-81. Because the basin is so large – it’s one of the world’s largest sedimentary aquifer systems, covering almost a quarter of Australia’s landmass – it takes as long as 1–2 million years for water entering the system in northern Queensland to filter out in discharge springs in South Australia, according to research by basin expert Dr Rein Habermehl. Water in the Great Artesian Basin moves at a rate of 1–5 metres per year through porous rock formations. Water age is measured by the concentration of environmental ‘tracers’, both man-made and natural.ĭalhousie Springs in Witjira National Park, northeastern South Australia, is a natural discharge point for Great Artesian Basin water. So how do scientists try to date water – and why do they bother? Praise for pollution “It’s not an accurate science as such, but you can say that 10% is five years old, 20% is 13 years old and so forth,” says hydrogeologist Dr Ilka Wallis, from Flinders University in Adelaide. Which means working out the age of water requires a slightly different way of thinking about the dating process: that glass of water you’re sipping might be 100,000 years old, two years old and 156 years old all at the same time.
That means the oldest Australian groundwater tested to date began trickling into aquifers around the same time as the first hominids were tiptoeing out of Africa.īut unlike the remains of those early humans, whose fossilised existence is trapped in static rock, water moves.
Australia is an ancient country, geologically speaking, and its groundwater aquifers reflect this: water in the Murray-Darling Basin has been dated to as old as 200,000 years, while some reservoirs in the Great Artesian Basin are thought to be nearly two million years old.
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