National Geographic: A "No Fishing" sign sits improbably along a dry desert road in Nevada. The largest man-made reservoir in the U.S., Lake Mead, once extended this far-but the watery destination of anglers and boaters has shrunk so much that the lakeshore now is about a half-mile away. (View an interactive map of the region.)
The recession of the massive lake that straddles Nevada and Arizona is symbolic of a long-standing problem that just got a lot worse: The Colorado River's record-low flows and the shrunken...