Interesting. This is the first time I've ever heard of this:
Interior Department agencies want to release a high volume of water from Glen Canyon Dam in Page, Ariz., into the Colorado River in early March in hopes that higher water flows will move sand out of the riverbed and restore sandbars throughout Grand Canyon National Park.
Sandbars throughout the 277-mile length of the park provide critical habitat for wildlife and protect archeological resources. High water flows also create backwaters needed by native fish, including the endangered humpback chub. Since the dam began blocking water in the early 1960s, a number of native fish species have died off and non-native plants have taken root, significantly disrupting the canyon's delicate ecosystem.