Making Rain

The good people of Toowoomba, Australia, a town of about 90,000 that sits atop the Great Dividing Range in southeast Queensland, have a branding problem on their hands. Residents of the nation's "Garden City" have not been able to use their sprinklers for nearly three years. Handheld hoses got the kibosh two years ago and, in 2006, watering the lawn by bucket was also banned.

Why? Toowoomba's residents are slowly running out of water, and have been for the past 15 years, along with nearly everyone else in this corner of eastern Australia. The region is undergoing its worst drought in over a century, and dead flower beds and brown football fields are the least of their worries. Toowoomba is the go-to city for a large rural area, including the nearby Darling Downs, fertile farm country until the rain went away and never came back. "We've been in water restriction in Toowoomba since 1992," says Dianne Thorley, the city's mayor of eight years. "Australia [is] drying up, like a dried apple."

The bad luck could end for Toowoomba and the rest of southeast Queensland. Last month a group of scientists in the area got one step closer to launching what could be the world's most advanced experiment in rainmaking — or, as it's known in weather circles, cloud seeding. That's the practice of injecting clouds, usually with silver iodide "seeds," salt or dry ice, to make the clouds' water or ice particles bigger and yield more rain. The technique has been used in different parts of the world for more than 60 years — with varying success. But the slow ramp up of weather technology — and an enduring human obsession to play with the sky — has kept the practice afloat during times of hard skepticism and dwindling funds.

Cloud seeding was developed in 1946 by scientist Bernard Vonnegut, brother of author Kurt. Countries quickly adopted it. Over the three decades following its introduction, the U.S. spent many millions of dollars a year on the technology. It was even used for a while during the Vietnam War to increase rainfall on the Ho Chi Minh Trail to hamper supply movement. By the 1980s, however, the science of cloud seeding acquired a snake-oil whiff, as disreputable private companies tried hawking it to desperate, drought-ridden communities. Within the decade, it had fallen out of favor.

Now, cloud seeding is back, especially in Australia. Energy company Snowy Hydro, for example, is trying to replenish dwindling snowfall in the not-so-Snowy Mountains in New South Wales. But what's special about the Queensland project, says Roelof Bruintjes, a cloud-seeding expert with the U.S. National Center for Atmospheric Research, is that, for the first time, scientists will be able to take full advantage of a simple premise: some clouds are better for seeding than others. Up to now, the right weather-measuring tools have never been in the right program at the right time. Starting in November, they will be. A project staff of about 30 will use a recently installed CP2 Doppler radar to analyze what's happening in Queensland's clouds before, during and after materials like silver iodide and salt are sprayed into them from planes. Working in tandem with other ground radars and forecasting equipment, the technology will be able to do a three-dimensional reading of the atmosphere — similar to a body scan. Not only will this mean better information about when conditions are right to send the seeding planes, but it will enable scientists to "watch" how the water and ice particles in the cloud are affected by the chemical. "This has not been done in any program anywhere in the world before," Bruintjes says. "Once we know what nature is producing in a specific region, we can determine how we can optimize this."

The Australia trial couldn't happen in a place that needs it more. Queensland's government has budgeted $7.6 million in public money into the four-year, multipartner experiment, part of a larger initiative to fight the crushing drought, including a desalination plant and a controversial program to recycle waste into drinking water. "We're in uncharted territory as far as rainfall goes," says Craig Wallace, the state's Natural Resources and Water Minister, who acknowledges that committing to cloud seeding — which still has its naysayers in the scientific community — may raise some eyebrows. "You'll always get skeptics, but we owe it to the people of Queensland to try everything we can."

Toowoomba Mayor Thorley sees it the same way. Like the state, her town has explored several options to get more water to people, from tapping into natural underground aquifers to pumping water some 700 m up the mountainside. "If we're seeing such weird weather — if we're going to have to pump water all over Australia via huge pipelines — wouldn't it be wiser to find another way?" says Thorley. "It would be worth a go."