A river awakens, bringing green magic to a desert town

After a week of stunning rain, the Todd River in Alice Springs flows again, bringing a beleaguered community together

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< p class= "css-at9mc1 evys1bk0">Whenever there is rain in the forecast for the desert town of Mparntwe, also known as Alice Springs, the same question usually arises: "Do you think that the Todd will sink?"

This week, the answer was yes. The normally dry Todd River swelled with water following a week of rain that fell 184mm (about 7.2 inches) from the sky after months of unrelenting heat, according to the Bureau of Meteorology. The rain picked up piles of debris, washed away roads and transformed the usually pastel red-yellow landscape of Australia's central region into a rich tapestry of brown-green.

Local authorities issued severe flood warnings, but in a region typically characterized by arid heat, people were excited – even more so when the water began to rise. People flocked to the banks of the Todd, reveling in the majestic sight of a moving river.

It's something that people in this part of the world can only see a few times a year. . Although the land is never completely dry (a rich water table can be seen through the rows of mature river red gum trees that line the banks), airflows of any significance depend on heavy rainfall.

John Wischusen, a hydrogeologist based in Alice Springs, said the usual formula for determining whether the Todd would sink was 40 millimeters of rain at a rate of 50 millimeters per hour. This is a heavy downpour typical of a summer thunderstorm, but he added that consecutive days of rainy weather at a lower intensity would also (and this week it has) tip the balance.

“It’s like a roof and a water tank,” Mr. Wischusen said, explaining how the high concentration of Precambrian rocks (including the gneiss and granite) in and around Alice Springs encouraged water runoff. “But the ground underneath has to be wet to a certain level before it can drain. This is why you need a certain amount and/or intensity of rain for water to flow over the ground and into river channels and through the city. »

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