Come the camanchaca.

• Author: Mooney, Michael J.
• Position: Chilean coastal town harness fog to solve water crisis

A once-parched coastal town in Chile is now flowering thanks to a binational project that allows residents to - literally - drink the fog

A broad bank of rumpled stratocumulus clouds drifts in soundlessly from the sea. Below, a bleak, parched coastline almost cries out for water, but the local population scarcely looks up anymore. Why bother? They know it won't rain.

There, along the dry Pacific ramparts of northern Chile lies the Atacama Desert: a barren, desiccated region that has suffered from chronic thirst on a geologic scale stretching back centuries and beyond human memory. It is an extraordinary area by any measure, where less rain falls per square mile than anywhere else on earth. Some parts of the Atacama have never reported rain.

Along the Atacama coast conditions are somewhat better thanks to increased moisture from the sea. Still, normal agriculture is out of the question, and coastal Chileans long ago looked offshore to survive by harvesting abalone, crab, and other shellfish. And so they ignored or cursed the perennial rainless clouds that promised only disappointment as a recurring part of their quixotic climate - until about a decade ago.

Typical of the region's fragile fishing villages is Caleta Chungungo, which lies squeezed between the coastal cordillera and the Pacific Ocean. About forty miles south is the regional port and capital city of La Serena; Santiago, the national capital, lies about 280 miles southeast, eight hours by road, and a century apart in time.

The residents of Caleta Chungungo live in modest homes defiantly painted in bright hues of green, orange, and blue, as if to dispel their often gray, always dry environment. Until the early 1970s residents received water from the El Tofo iron mine, sitting atop a twenty-five hundred-feet-high mountain ridge about four miles inland. But when the mine closed, the villagers were forced to subsist on semicontaminated water trucked weekly from about twenty-five miles away. Daily water usage averaged about 16 quarts per capita, while in the U.S., average use runs 360 quarts per person daily. Fully 10 percent of Chungungo's meager income went to staving off terminal thirst, despite a government subsidy that never met its avowed goal. For residents, the very idea of a bath was a luxury too ludicrous to imagine; skin and digestive infections flourished.

But why this perennial water crisis in a subtropical latitude where rain should be plentiful? What is the Atacama, and why is it perennially dry?

On a map of western South America Chile lies sandwiched between the high Andean cordillera to the east and the Pacific Ocean to the west. The narrowest nation on earth, Chile stretches south some twenty-seven hundred miles from the Peruvian border, like a thin crooked sword, over thirty-eight degrees of latitude. Though roughly...