Here’s an excellent article on management of the Grand Canyon’s geomorphology from the Christian Science Monitor.
I’ve had the pleasure of hearing Jack Schmidt (a key researcher in this effort). He’s a dynamic and fascinating speaker on river management and geomorphology, catch him if you get the chance. He regularly teaches at workshops, including this one (where I’ve taught, and where I met him).
A quote from the article:
“Artifacts of the existence of the dam are the clear water, the cold water, and steady low flows,” says Jack Schmidt, a watershed sciences professor from Utah State University. The tamed river, devoid of sand (close to 98 percent is stopped by the dam), now erodes through the sandbars and carries the sediment into Lake Mead, where it’s trapped behind Hoover Dam. According to researchers, the new behavior of the river has led to narrower rapids, eroded beaches, invasion of nonnative vegetation, and the loss of native fish. The Colorado River now has nearly twice as many nonnative fish species (60) as native ones (32), with the humpback chub population declining from 10,000 in 1989 to 6,000 in 2006.
More on this topic, and lots of links, from the USGS here.
(BLM photo from the CSM article.)