Henry Brean has a story in this morning’s Las Vegas Review-Journal on the mess at the upper end of Lake Mead where the Colorado River used to empty out into a lake, dumping its sediment. Now that the lake level’s dropped, the river’s cutting back down through all that deposited glop, creating a new rapids:

Since drought took hold on the Colorado River in 2000, the water level at Lake Mead has fallen more than 100 vertical feet. The drop has left the Colorado to reclaim dozens of miles of terrain in northwestern Arizona where the recreation area meets Grand Canyon National Park.

“It wasn’t even a river there. It was a lake,” said Mark Grisham, executive director of the Grand Canyon River Outfitters Association.

But instead of obediently returning to its historic channel, the river has carved a new course through the thick layer of silt that began collecting when Hoover Dam was finished in 1935. Just downstream from the old Pearce Ferry boat ramp, that new channel “runs right smack into a wall and turns,” Grisham said.