NASA has posted a set of registered satellite images of Lake Powell from 1999 to 2009, showing dramatic changes in water levels, as part of its Earth Observatory 10th Anniversary recognition. NASA commentary states that according to the U.S. Bureau of Reclamation, "Lake Powell’s water level hovered around 20 million acre-feet in 2000. By 2005, it had dropped to roughly 8 million acre-feet."
[Left, 1999. Right, 2008. Credit NASA]
[thanks to Kevin at The GeoChristian for spotting this]