One old resident from Arizona said he walked to the edge of a lake on a boardwalk leading to a small wharf, where a boat was moored. He counted 30 steps since he passed the whereabouts of this wharf … 10 years ago. This lake dries up almost visibly.

Big Lake Powell, an extension of the Colorado River straddling Arizona and Utah, has come down to one-third of its original level. And that’s the least of the problems. The real fear is that 30 million Americans risk losing a war that threatens the future of the entire southwestern United States.

Without the Colorado River, economic development in the southwest would never have occurred, says the Save the Colorado River coalition. Las Vegas would be an unknown village and most of Nevada, Arizona and Utah, vast, soulless deserts. The river has become the most important artery of this region which, writes the Sierra Club, “is drier than the deserts of North Africa”.

Lake Powell is artificial: it is a reservoir – like those of the Hydro-Québec dams – born at the turn of the 1960s when the Glen Canyon Dam was built. The same is true of his twin brother, Lake Mead, born 30 years earlier from the construction of the Hoover Dam near Las Vegas. The gradual drying up of both, in the last decade, results both from an unconsciousness in the face of a river treated as if it were unlimited, and from enormous errors of calculation.

More than a thousand years ago, handfuls of Native Americans cultivated corn in this semi-desert region because they had found the Colorado River there. But today, millions are taking the opportunity to water their lawns, grow fruits and vegetables in the desert, develop suburbs and maintain golf courses – about 150 just in Phoenix, capital of Arizona, and 130 in Las Vegas, Nevada. Local junk removal services are thriving due to the increase in urbanization and all the pollution that comes with it.

The Central Arizona Project, a canal that transports 541 km of river water to the 4 million population of the Phoenix area, is the largest water system in the United States. In the end, the Colorado river is running out of steam, Lake Powell is drying up, and the small wharf at Wahweap Campground where people have been walking has to be moved a little further, year after year.

The Colorado meanders for 2330km: it rises at the summit of the Rockies in the state of Colorado, where it is fed by melting snow, and it flows to Mexico, after crossing, among others, the famous Grand Canyon. Except that since the year 2000, when it reaches the Pacific on the Mexican side, more exactly the Sea of ​​Cortes … it is dry. Everything was pumped. And if the Mexicans are entitled to a party – which allowed them to set up farms and feed the city of Tijuana – it is because of a treaty of 1922 (Colorado River Compact) which defines virtually the drop by the flows that can be taken by the seven US states concerned.

Since 1922, the population has exploded. Las Vegas has sprung up from the desert. Arizona has become the fastest-growing US state-with the influx of retirees from the east coast. And there is agriculture. As a result, more water is pumped into Colorado than the river carries. This is where the miscalculation occured. Lake Mead in 1935, and Lake Powell in 1962, were to serve as a reserve, to compensate for years when the river level would be too low. They used the average precipitation over a decade … and now we see that it was a period of above average precipitation. For 11 years, it has hardly rained.

Lake Powell is down to 30% of its original level, and Lake Mead is at 50%. All around Lake Mead, a huge white ring – of calcium – photographed by visitors to the Hoover Dam, marks the height that the water reached. The level of Lake Mead has come down so low that Las Vegas and Nevada have started building a new pumping system, installed deeper into the lake, because the current system may soon be out in the open. Cost, by 2014: nearly a billion.

Recently Las Vegas experienced a major storm (flash flood), which killed one person, flooded about forty homes and temporarily blocked two highways and the airport. The end of water shortages? Not quite: the storm left … three inches of rain. It was too much of a sudden for the drainage systems, but it would take more to bail out Lake Mead, whose level depends mostly on the snow melt in the Rockies -and a little near tributaries, like the river Virgin.