A thick, white band of newly-exposed rock face stretches high above boaters' heads at Lake Powell - a sharp contrast against the famous red desert terrain and a stark reminder how far the water has fallen. Just last year, the water was more than 50 feet (15.24 meters) higher at the popular destination for houseboat vacations. This summer, the climate-change-fueled megadrought engulfing many parts of the U.S. West touched off a grim milestone at Lake Powell when water levels hit historic lows.