Lake Las Vegas, Oct. 2010

If all goes well weather wise over the next six weeks, the US Bureau of Reclamation will release a substantial slug of extra water in 2011 to help refill Lake Mead.

Thanks to a decent snow pack, there is currently a 71 percent chance that the big reservoirs on the Colorado, Mead and Powell, will be operated in “equalization” status this year. That means an extra release from Lake Powell that, if things hold up, will be the largest since 1998 (11.5 million acre feet). That would leave Lake Mead’s elevation at 1,105 feet above sea level at the end of the water year Sept. 30, 21 feet above a year earlier.

Worth noting: The release is more than 3 million acre feet above the Upper Basin’s Colorado River Compact-required release. But storage in Lake Mead will only increase by 2 million acre feet, because of the Lower Basin’s propensity to use lots of water no matter what. (See here for previous discussion of the overdraft problem.)

The final decision on release plans is done in early April, based on the April 1 snow pack and accompanying runoff forecast.

Source: USBR February 2011 24-month study (pdf)