Bump and update: From Time (Bryan Walsh):
What’s causing Lake Mead to dry up—and what does it mean for the Southwest? The one undeniable cause is simple growth—Las Vegas has grown from 25,000 people in 1950 to some 2 million today. That means more lawns, more laundry, more swimming pools, more car washes—in general, more straws sucking the water out of Lake Mead. And of course Las Vegas isn’t the only area in the Southwest to experience booming growth over the past few decades. From Denver to Phoenix to Los Angeles, the once lightly populated West has exploded, even as farmers in the region draw more water from the system to irrigate the desert.
But the Southwest has also been caught in a devastating drought that has now gone on for more than 10 years, one that has reduced the region’s water supplies even as growth has further stressed them. Drought is a natural phenomenon—especially in the desert, go figure—and there have been varying levels of rainfall in the region just in the 75 years since Lake Mead was first filled. But the scary thing is that the territory might be more vulnerable to drought than it seemed during the 20th century—a time period that may have been unusually wet on a historical scale. A 2007 panel organized by the National Research Council found evidence that mega-droughts had occurred in the Southwest more frequently than had been thought, and that “drought episodes are a recurrent and integral feature of the region’s climate.” The Colorado River Compact—which divides up water supplies for seven U.S. states and parts of Mexico—was drawn up in 1922, based on river flow data going back to the 1890s, a time of unusual wetness. We may have built the Southwest with a false sense of water security.
Then there’s climate change, an X factor for future water supplies. It’s difficult to gauge what impact, if any, global warming may have had on the current drought and on dropping water levels. As always, it’s virtually impossible to filter out climate change as a cause for a natural disaster amid all the noise and static of other factors. But as the recent report from the government U.S. Global Change Research Program shows, the Southwest is already rapidly warming, reducing the spring mountain snowpack that helps feed the rivers of the region. We’re likely to see increasing temperatures in the future, with more frequent drought and increasingly scarce water supplies. Climate change won’t be the only cause behind the drying of the West, but could make a bad situation much, much worse.
From The New York Times (Felicity Barringer):
“It is a record-setting moment,” said Colleen Dwyer, a spokeswoman for the Bureau of Reclamation. She added that slightly more water than usual had been released through Hoover Dam over the weekend because the power marketing agency that sends dam-generated electricity around the Southwest had requested some additional flow.
Lake Mead’s levels are still eight feet above the level at which a shortage is officially declared and limited rationing could go into effect for users in Nevada and Arizona, and well above the levels when the Hoover Dam’s hydroelectric output might be seriously jeopardized.
But Barry Nelson, a senior policy analyst for the Natural Resources Defense Council, said: “This strikes me as such an amazing moment. It’s three-quarters of a century since they filled it. And at the three-quarter-century mark, the world has changed.”
More coverage from the Arizona Republic (Shaun McKinnon):
Not since it was first filling in 1937 has Lake Mead held so little water. The reservoir’s level fell to the historic low shortly before noon on Sunday, eclipsing a previous record from the drought-stricken 1950s. The lake is now just 8 feet above the level that would trigger the first drought restrictions, which would reduce water supplies for Arizona and Nevada. That gap could close by next year – the reservoir fell 10 feet from October 2009 to 2010 – but there are measures in place that would likely delay rationing for one or two years or even longer if a wet winter increased runoff into the river. Most homes and businesses in Arizona likely would not feel the direct effects of the restrictions, which would divert water first from farmers.
But conservation groups say the reservoir’s low levels underscore the risk to the Colorado River. “Everyone needs to know when we turn on the tap, it drains water out of the river and it has ecological consequences,” said Gary Wockner, campaign coordinator for Save the Colorado, a non-profit education group based in Fort Collins, Colo. “We need to try to keep some water in the river and keep it alive.”[…]
The three lower-river states, along with Colorado, New Mexico, Utah and Wyoming on the upper river, approved a drought plan in 2007 that uses Lake Mead water levels to trigger incremental rationing, part of an attempt to avoid widespread shortages. The first trigger is at 1,075 feet above sea level. The reservoir reached elevation 1,083.18 feet around midday Sunday and was at 1,083 feet by Monday afternoon. The previous low level was 1,083.19 feet, set in 1956…Under the 2007 plan, the first trigger would reduce water deliveries to Arizona by a little more than 11 percent, or 320,000 acre-feet, and to Nevada by about 4 percent, or 13,000 acre-feet. Additional reductions would occur if the lake continued to drop.
More coverage from the Las Vegas Review-Journal (Henry Brean):
Since drought took hold on the Colorado and its tributaries in 1999, the surface of Lake Mead has plunged almost 130 feet and caused fits for the National Park Service and its marina operators who must extend roads, utilities and other services to reach the shrinking shoreline.
The lake’s decline poses major problems for the Southern Nevada Water Authority, which draws 90 percent of the Las Vegas Valley’s drinking water from intake pipes that will start to shut down should the lake fall another 33 feet. “I’m worried,” authority General Manager Pat Mulroy said. “We’re trying everything we can to keep as much water in Mead as we can.” The prognosis looks bleak. Mulroy said federal climate forecasters are predicting abnormally dry conditions during the next two winters in the mountains that feed the Colorado…
The previous low-water mark for Mead came 54 years ago, on April 26, 1956, when the drought-stricken lake bottomed out at 1,083.19 feet above sea level. According to the Bureau of Reclamation, the lake hit elevation 1,083.18 between 11 a.m. and noon Sunday and continued to fall. By Monday afternoon, it sank below elevation 1,083 as water was released through Hoover Dam to meet orders downstream from cities and farms in California and Arizona. Projections by the U.S. Bureau of Reclamation call for Lake Mead to reach a low point of 1,082.1 on Nov. 2. Then it is expected to rise by about 8 feet through the end of February before starting back down again. Water forecasters expect the lake to hit another record low by May and shrink below elevation 1,077 by September…
Even at its lowest level since it was first filled, Lake Mead remains the largest man-made reservoir in the United States. The falling water level has caused some problems with access, but it has also unveiled new coves and pristine beaches that used to be underwater, Roundtree said.
More coverage from the Voice of San Diego Environment (Rob Davis):
Millions of people — San Diegans included — rely on the reservoir’s water. So what does its drop mean here? In the short term, nothing. It doesn’t have any impact on San Diego’s supply even though we relied on the river for 61 percent of our water in 2009. But it does send a bad signal that the river supplying the Southwest’s lifeblood is continuing to face pressure — a pressure that scientists say is growing as the climate warms. If the lake continues dropping, it will first cause problems for cities in Arizona and Nevada before San Diego. Those states hold lower-priority rights to Colorado River water than California does.
More Colorado River basin coverage here.
