US, Mexico Agree To Controlled Flood In Effort To Revive Colorado River Delta
FROM above it looks like a meandering yellow scar. On either side lie lush green polygons – the irrigated fields of the Mexicali valley just south of the US border, where tomatoes, cucumbers and onions grow in what should be a desert. The dusty smear running in between used to be the Colorado river. It's been decades since it has reached the sea. On 23 March, it will begin its journey back from the dead. In an ecological experiment unprecedented in US history, seven states and two countries have signed an agreement to unleash a huge pulse of water designed to bring the river's dwindling delta back to life.
"We're trying to engineer a spring flood," says Karl Flessa, a geoscientist at the University of Arizona who is leading the team that will study how the delta responds. "This is a river system that historically had a huge spring flood every year. We're trying to recreate that."
Before development of the American south-west led to the widespread damming of the Colorado from the early 1900s onwards, the floods that fed the river's delta kept it teeming with life. When explorer Aldo Leopold canoed the delta in 1922, he marvelled at "a verdant wall of mesquite and willow" that separated the river from the desert. Jaguars prowled outside the few human camps that existed. To try to bring back this lost ecosystem, Flessa and his team are planning to release a one-time, 130-billion-litre pulse of water.
The water that will make up the pulse is currently being slowly released from behind the Hoover, Davis and Parker dams. It will collect behind the most southerly dam on the river, the Morelos, which sits on the Mexico-US border and normally diverts the last of the Colorado toward agricultural land.
EDIT
http://www.newscientist.com/article/mg22129602.800#.UyEwmM5s08o