Colca's elusive waters.

• Author: Moore, Patti
• Position: Peru's Colca Canyon and Colca River Valley

AT DAWN, pink-feathered clouds of flamingos seem to nail the icy waters near the source of the Colca to the ground with their spiky legs. But the water escapes them and a newborn river meanders off on its search for the sea. Sixty miles away, an Andean condor stretches its wings, tests the thermals and settles back into a rocky niche to wait until the sun has warmed the air enough to lift its heavy body. The silver ribbon of the river, 3,000 feet below the condor's feet, now churns and foams its way to the coast.

Like the condor, the farmers of the Colca Valley for centuries have watched the Colca River below their feet, tantalizingly out of reach of their fields on its headlong plunge to the Pacific. The Colca River was never a generous provider. Near its source, where the water is easily accessible, cold and wind make farming impractical or impossible. As the river nears the fertile soils of the valley, it perversely dives deep into the living rock, becoming an artery of the earth itself, pulsing through its forbidding canyon.

Below the canyon, tractors criss-cross new fields as Colca water, diverted through a maze of dams and canals for a coastal irrigation project, begins to bring green life to some of the driest desert on earth. Above the canyon, in the valley, farmers continue to irrigate their narrow terraces using techniques that have changed only slightly over the centuries.

Site of some of the most extensive agricultural terraces in Peru, the Colca Valley, four hours north of Arequipa, stretches like an exclamation of human accomplishment between natural phenomena that come to seem common-place to a frequent traveler in the Andes. Snowcapped peaks, many of them volcanoes, close around it like parentheses. From the valley's northern side, a few hundred miles from the Pacific Ocean, the hardy can climb to the headwaters of the mighty Amazon. At the downriver end of the valley, undulating terraces taper off into barren rock at the head of the canyon. At its deepest point of 10,607 feet, the Colca is more than twice the depth of the Grand Canyon, making it the world's deepest gorge.

The Colca Valley alternately has been isolated and exploited since prehistoric times. It was a highly productive agricultural center long before its incorporation into the Inca empire. When the conquistadors arrived in 1547, they found large herds of llamas and alpacas, a well-developed system of terrace running approximately 40 miles along both sides of the valley, and a thriving population of 60,000 to 70,000. They also discovered silver and took farmers off the land to work the mines. By the time the mines played out in the late 1700s, European epidemics and forced labor had reduced the population to a fraction of its pre-Conquest level, and the Colca Valley ceased to be a major agricultural center.

In 1929, two U.S. pilots, Robert Shippee and George Johnson, "discovered" the Colca Valley and Canyon for the modern world during an aerial geographic expedition to southern Peru. Gonzalo de Reparaz, a Spanish geographer and cartographer working for UNESCO, "rediscovered" the area in 1954, again from the air. It was Reparaz who made the...