This story is part of a special series that explores the global water crisis. For more clean water news, photos, and information, visit National Geographic's Freshwater website.
The headwaters of the Pascua River spring from glacier-fed Lago O'Higgins in one of the most remote parts of Chilean Patagonia (pictured in February 2010). Few people visit these headwaters, or see any other stretch of the Pascua as it roars for 40 miles (62 kilometers) through remote forests and canyons of the South American wilderness, conservationists say.
"As far as the eye can see here, you don't see anybody or anything but unclimbed mountains and unrun rivers," said Trevor Frost, a former National Geographic Young Explorer who helped to document the region with the International League of Conservation Photographers.
"We stand to lose something that few people have ever personally experienced."
That's because the Pascua—like its neighbor the Baker River—is threatened by a massive hydroelectric project that would shackle these rivers with five dams by 2020. The plan would flood more than 15,000 acres (5,900 hectares) of the vast Patagonian wilderness at the bottom of South America, and spawn a stretch of powerlines some 1,500 miles (2,450 kilometers) long to distribute energy created by the rivers.
To document what's at stake, the International League of Conservation Photographers sent a team of world-renowned photographers, writers, and filmmakers to Patagonia as part of a Rapid Assessment Visual Expedition (RAVE). They returned with thousands of images—some of them presented here.Brian Handwerk