UPDATE: I ran across this piece on Lake Meade today.
In 2012 I visited Lake Meade and Hoover Dam and I was immediately struck by the white line around the lake. It looks like it is painted on but it is actually a mineral deposit that shows where the water has been in the past. People now refer to it as the bathtub ring. Things were so bad, I really thought that natural cycles would cause it to resolve itself by now but it has not. The drought relentlessly continues. The lake is now down to roughly 40%, by volume, of its maximum capacity. Since the water level is low, the head for the generators is less. This substantially diminishes the electrical generation from the dam. In 2012 wrote a blog post about it here. Las Vegas is so concerned that they are building a new tunnel to provide access to the water deeper down, their current tunnel intake may soon be above the water line and unable to sip water from the lake.
This New York Times article does a nice job of communicating the magnitude of the problem. For the first time they are reducing flow from Lake Powell. With the water already at record low levels this promises to make water politics out West get pretty interesting. In the NYT article they mention that the 20th century was a relatively wet century as far as the Colorado is concerned. So even without climate change the scenario unfolding is not as surprising as the public has been led to believe. But add climate change to the lower typical flow and we are looking at a challenging scenario for the 21st century.