Let Your Waters Wash Down

Fairport Convention: Ballad of Easy Rider

The river’s isolation and secrecy, however, were only part of what made it superlative. There was also its vertical drop. The Colorado’s watershed encompasses a series of high-desert plateaus that stretch across the most austere and hostile quarter of the West, an area encompassing one-twelfth the landmass of the continental United States, whose breadth and average height are surpassed only by the highlands of Tibet. Each winter, storms lumbering across the Great Basin build up a thick snowpack along the crest of the mountains that line the perimeter of this plateau---an immense, sickle-shaped curve of peaks whose summits exceed fourteen thousand feet. As the snowmelt cascades off those summits during the spring and spills toward the Sea of Cortés, the water drops more than two and a half miles. That amounts to eight vertical feet per horizontal mile, an angle that is thirty-two times steeper than that of the Mississippi. The grade is unequaled by any major waterway in the contiguous United States and very few long stretches of river beyond the Himalayas.

(The Nile, in contrast, falls only six thousand feet in its entire four-thousand-mile trek to the Mediterranean.) Also unlike the Nile, whose discharge is generated primarily by rain, the engine that drives almost all of this activity is snow. This means that the bulk of the Colorado’s discharge tends to come down in one headlong rush. Throughout the autumn and the winter, the river might trickle through the canyonlands of southern Utah at a mere three thousand cubic feet per second. With the melt-out in late May and early June, however, the river’s flow can undergo spectacular bursts of change. In the space of a week, the level can easily surge to 30,000 cfs, and a few days after that it can once again rocket up, surpassing 100,000 cfs. Few rivers on earth can match such manic swings from benign trickle to insane torrent.
--Kevin Fedarko
The Emerald Mile