How will the current La Niña effect Lake Mead’s water level

A full Lake Mead back in the day

From The New York Times (Paul Quinlan):

July not only saw the lake drop to 1956 levels but also brought cooling temperatures in the Pacific Ocean that signaled a developing La Niña system, historically a harbinger of more hot and dry weather. The La Niña “appears to be strong, and it might even last two years,” said Brad Udall, director of the National Oceanic and Atmospheric Administration’s Western Water Assessment program at the University of Colorado.

In the 75 years since the workers began to hold back the Colorado River behind the Hoover Dam, the lake’s water has taken two precipitous plunges: first during the prolonged drought of the 1950s, which ranks second only to the current dry spell, and again in the mid-1960s, when water managers began filling Mead’s cousin 250 miles upstream, Lake Powell.

Neither dip was as severe or prolonged as that of the past decade. Nearly full in 1999, Mead has shrunken to 40 percent capacity, causing the ominous, bleach-white bathtub ring on the surrounding mountainsides to grow taller by the year. In the past five months, the lake steadily shed another 15 feet, to about 1,087 feet above sea level today. Four more feet and the lake surface will hit what would be the lowest mark since 1937 — something the government projects will happen in October…

Federal water managers have the option, under certain conditions, to boost Mead’s supplies by releasing water from Lake Powell — an option that they may be forced to exercise but that amounts to little more than the water management equivalent of Whac-A-Mole…

Federal officials attempted to address the problem in 2007, striking a landmark “shortage sharing” agreement with Western states that dictates increasing cutbacks to Mead’s water deliveries as the surface drops. Other efforts are under way, including creative water conservation programs like “Cash for Grass” in Las Vegas, which pays homeowners $1-per-square-foot to convert to desert landscaping. The feds are also building new reservoirs, such as the relatively tiny, soon-to-be-completed Drop 2 Storage Reservoir, built to catch and save excess water sent downstream from Mead that would otherwise flow into Mexico, unused by the United States…

Greater cutbacks and impacts follow as Mead’s surface plunges further. When the 28.5-million-acre-foot reservoir’s surface hits 1,050 feet, or about 26 percent capacity, deliveries get slashed by 417,000 acre-feet, Las Vegas shuts down one of its two intakes and Hoover Dam’s massive turbines lose the hydraulic pressure needed to generate electricity. The maximum cutback of 500,000 acre-feet kicks in when Mead’s surface hits 1,025 feet, or about 20 percent capacity…

Studies and models like these prompted Reclamation to launch a two-year study in January that will take a more detailed look at water supply and demand in the region. Fulp said the study will inform decisions about, among other things, how Mead’s water gets meted out in the coming decades. “The risk of losing Lake Mead is negligible,” Fulp said. “We’re not going to drive this lake into the ground, probably. I don’t mean to say it absolutely couldn’t happen, but I believe we’ve got these management options in place so that it wouldn’t happen. We would cut deliveries back.”

More Colorado River Basin coverage here.

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