During the West’s last nine years of drought, the level of Lake Mead, which backs up behind Hoover Dam, has plummeted 100 vertical feet, causing unexpected and peculiar things to happen. Where there used to be flat water with no pizzazz on the reservoir’s edge 120 miles east of Las Vegas, a dangerous rapid has emerged. “The so-called Pearce Ferry Rapid features a sharp drop and a hard right turn, as the Colorado River tumbles around a rock outcrop,” says the Las Vegas Review-Journal. In fact, the new rapid is so fierce that one rafting Web site rates it as Class 4, on a scale of 1-6. This is not the kind of problem the National Park Service is used to dealing with at Lake Mead, says Mark Grisham, who heads the Grand Canyon River Outfitters Association: “There is an irony there that these flat-water guys are now dealing with whitewater issues.” What makes the new rapid so challenging, he adds, is that it “runs right smack into a wall and turns.” The falling reservoir level forced the Park Service to close its boat ramp at Pearce Ferry in 2002. Now, however, it plans to build a two-mile dirt road for boaters just upstream from the rapid.