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September 23, 2017

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A wet May brings rare good news for Lake Mead water projections

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L.E. Baskow

Lake Mead is at its lowest level since being filled in the 1930s.

Updated Monday, June 15, 2015 | 6 p.m.

Third Straw Intake Tunnel Tour

Jim Nickerson, project manager, talks with Claudio Cimiotti, senior tunnel engineer, before a media tour of the third intake tunnel at Lake Mead Monday, June 1, 2015. Launch slideshow »

An exceptionally rainy month in Colorado that's been hailed by some as a "Miracle May" is providing a much-needed boost to the drought-stricken Colorado River basin and could help delay mandatory water cuts in Las Vegas and Arizona, according to projections released today by the Bureau of Reclamation.

Following another winter with less than average snowfall in the Rocky Mountains, forecasts for the health of the Colorado River were gloomy, with Lake Mead's elevation projected to drop to 1,077 feet by next January, dangerously close to the 1,075 foot elevation threshold that would trigger mandatory cuts in water supplies.

But a series of heavy storms across the basin last month led to higher than normal precipitation and even some snow at higher elevations that could pour as much as 1.5 million additional acre-feet into Lake Powell, the Colorado River's upstream reservoir.

While that won't be enough to make up for the decreased snowfall this year or to make a dent in the long-term depletion of the system, it does provide some breathing room for water managers.

At Lake Mead, the additional precipitation is enough to slow down the projected decline in lake elevation at least in the short term.

The projections released today show Lake Mead's elevation next January at 1,083 feet, a six-foot increase compared to projections made last month. Looking further out, projections for January 2017 have been revised to 1,079 feet, 16 feet higher than had been projected for the same time period just a month ago.

It's important to note that the Bureau of Reclamation's projections are revised monthly, and the outlook can change drastically based on snowfall and precipitation. Official water management decisions for the upcoming year will be made based on projections released in August.

But the increased precipitation in May could be enough to forestall mandatory cuts in water supplies for at least another year or two.

The reductions, decided as part of a 2007 agreement, would be imposed once Lake Mead's elevation falls below 1,075 feet in January of a given year. That would trigger a 320,000 acre-foot cut for the Central Arizona Project, which provides water to Phoenix, Tucson, farmers and other Arizona communities. That's equal to about 11 percent of its total Colorado River allocation. Las Vegas would lose 13,000 acre-feet under the cuts, equal to about 4 percent of the region's allocation, but residents wouldn't be affected because the region has already conserved enough to weather any potential reduction.

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