Fact: Over the last 25 years, rainfall in the western Australia city of Perth fell 20%.
The flow of water into Perth’s reservoirs fell 75%.
And Perth--a beautiful city, with much of the casual, creative attitude of San Francisco--became the developed-world city that came closest to simply running out of water.
In places that are experiencing climate change, there’s no debate about whether it’s “real” or not, like the debate we seem to enjoy having here in the U.S.
Where climate change is happening every day, its consequences are obvious, devastating--and often costly.
Perth had to scramble to both reduce water use and to find a solution to its sudden water shortage. Perth residents have, in the last five years, cut their per-person water use by 20%, saving an amount of water equivalent to that usually churned out by a large, expensive desalination plant. Perth has still had to construct a large, expensive desalination plant--the first of a half-dozen either finished or under construction across Australia. That nation has struggled to adapt to an era when (recent flooding notwithstanding) water disappeared from the places people had been collecting it for a century.
Perth’s desal plant now supplies about 20% of the city’s water, and officials consider it the city’s “climate independent” source of water. It is supplied with electricity using a wind farm, so the solution to climate-caused water scarcity didn’t make that scarcity even worse.
Why should we care about climate change in Perth?
Yesterday, the U.S. Interior Department  released a report predicting that climate change could cut stream and river flows in the Western U.S. by 8 to 20%, in river basins that supply water to almost one in 10 Americans.
Those western states--Colorado, Utah, Nevada, Arizona--are already parched after a decade of lower flows than we’ve come to expect. At the same time, they are located in some of the fastest growing regions in the U.S.
Modestly reduced rainfall often translates into dramatically reduced flows to humans, because dry ground absorbs water much more quickly, and because rain often ends up falling in places where we haven’t set up reservoirs.
The Interior report also predicts a temperature increase in the Western U.S. of five to seven degrees and reduced April 1 snow pack levels throughout the region. The April 1 snow pack is a standard way to gauge seasonal river flows.
The results could be devastating for water supplies from Denver down to Tucson and Las Vegas --it could change the water culture of those communities, and also their budget priorities.
That’s why we should pay attention to the lessons of Perth. It took water professionals and elected officials years to realize that water availability was changing. Once the problem really sank in, it was a crisis, and leaders had to scramble--water became a hot political issue, and smart decisions got hard to make. (One candidate for state premier suggested building a canal to supply water to Perth that would have been the equivalent of supplying water to Las Vegas by building a canal from Niagara Falls.)
In just the last five years, relative to population, Australians have had to spend the equivalent of half of President Obama’s stimulus program, just on water and water systems. The cost of the desalination plants alone comes to $14 billion--$646 for every man, woman and child of Australia, just on desal plants.
We have plenty of warning about what’s happening to water sources in the U.S., plenty of time to make good decisions that don't require crisis-level spending.
There will be no satisfaction in looking back from 2051 and seeing that the Interior Department’s 2011 report  was correct.
Adapted from The Big Thirst: The Secret Life and Turbulent Future of Water , to be published in April by Free Press / Simon & Schuster. © 2011, Charles Fishman.
Read the feature from Fast Company's April issue .
Read more from The Big Thirst on FastCompany.com .
[Image: Flickr user Ellen van den Berg ]