High good, low bad: Mead in 2011

When the federal Bureau of Reclamation recorded the closing elevation of Lake Mead to be almost 1,133 feet at midnight, December 31, the 2011 rise in the largest storage reservoir on the Colorado River was more than 46 feet, the first annual gain since 2005 and the largest since 1957 — so big that the decanting of last year’s snowpack has been causing a series of earthquakes in the Arizona desert. As Mead hits 56% full, and the other major storage reservoir on the Colorado, Lake Powell, sits at 66%, the bad news is that snowpack building up this year around the Colorado’s headwaters in the Rockies is significantly down, as is Northern Californian snowpack in the Sierra. Locally, rainfall is also below normal. By way of explaining the artwork, the Reclamation graphic above contrasts projected flow and demand in a river supplying roughly a third of Southern California’s water.