Century of Water Shortage Ahead? Lake Mead Drops Below Rationing Line For First Time in Its History.

Lake Mead Drops Below Rationing Line For First Time in Its History.

1075 feet. That’s the water level Lake Mead must stay above before mandatory multi-state water rationing goes into effect. A level just 25 feet above the highest intake pipe used to supply cities across the Desert Southwest. Last night water levels at the key national water storage facility fell below that hard line to 1074.99 feet — a record low never before seen in all of its history.

If water levels remain below the 1075 foot mark through January of 2016, then a multi-state rationing will go into effect (with most acute impacts for Arizona and Nevada). A rationing that will have serious consequences for desert cities across the Southwest, cities like Las Vegas which rely on Lake Mead for so much of their water.

Despite Lake Mead hitting the 1075 hard line, it appears that rationing may be forestalled through 2016. It’s a silver lining of all the severe summer storms that have rolled through the Colorado River Basin this spring and summer — pumping up water flows to Lake Mead and Lake Powell. A flush of much needed moisture that will, hopefully, prevent water rationing from going into effect during 2016. But prospects for the future, despite this temporary respite, are starting to look a bit grim.

Risk of Future Megadrought

The trend set in place by a human-forced warming of the Desert Southwest has resulted in an increasing number of dry years. The added heat forces water to evaporate more rapidly. So even when it does rain an average amount, moisture levels still fall. The result is not only an increase in single year droughts, but an increased risk of decadal droughts (called megadroughts).

As the years progress and more of the impacts of human-forced global warming become apparent, the drought impacts and severe drought risks are only expected to rise. For according to a recent Cornell University report (2014) the chance of a 10 year drought for the US Southwest under a moderate warming scenario (RCP 4.5) is 50% this century (greater for states like Texas, Oklahoma, New Mexico, Arizona, and Nevada — see graphic below). The chances of a 30 year drought range from 20-50 percent depending on the severity of the human greenhouse gas emission. More

 

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Dry Heat

Last week, Lake Mead, which sits on the border of Nevada and Arizona, set a new record low—the first time since the construction of the Hoover Dam in the 1930s that the lake’s surface has dipped below 1,080 feet above sea level.

The West’s drought is so bad that official plans for water rationing have now begun—with Arizona’s farmers first on the chopping block. Yes, despite the drought’s epicenter in California, it’s Arizona that will bear the brunt of the West’s epic dry spell.

The huge Lake Mead—which used to be the nation’s largest reservoir—serves as the main water storage facility on the Colorado River. Amid one of the worst droughts in millennia, record lows at Lake Mead are becoming an annual event—last year’s low was 7 feet higher than this year’s expected June nadir, 1,073 feet.

If, come Jan. 1, Lake Mead’s level is below 1,075 feet, the U.S. Bureau of Reclamation, which manages the river, will declare an official shortage for the first time ever—setting into motion a series of already agreed-upon mandatory cuts in water outlays, primarily to Arizona. (Nevada and Mexico will also receive smaller cuts.) The latest forecasts give a 33 percent chance of this happening. There’s a greater than 75 percent chance of the same scenario on Jan. 1, 2017. Barring a sudden unexpected end to the drought, official shortage conditions are likely for the indefinite future.

Why Arizona? In exchange for agreeing to be the first in line for rationing when a shortage occurs, Arizona was permitted in the 1960s to build the Central Arizona Project, which diverts Colorado River water 336 miles over 3,000 feet of mountain ranges all the way to Tucson. It’s the longest and costliest aqueduct in American history, and Arizona couldn’t exist in its modern state without it. Now that a shortage is imminent, another fundamental change in the status quo is on the way. As in California, the current drought may take a considerable and lasting toll on Arizona, especially for the state’s farmers.

“We need to stop growing alfalfa in the deserts in the summertime.”

Robert Glennon, water policy expert at the University of Arizona

“A call on the river will be significant,” Joe Sigg, director of government relations for Arizona Farm Bureau, told the Arizona Daily Star. “It will be a complete change in a farmer’s business model.” A “call” refers to the mandatory cutbacks in water deliveries for certain low-priority users of the Colorado. Arizona law prioritizes cities, industry, and tribal interests above agriculture, so farmers will see the biggest cuts. And those who are lucky enough to keep their water will pay more for it.

According to Robert Glennon, a water policy expert at the University of Arizona, the current situation was inevitable. “It’s really no surprise that this day was coming, for the simple reason that the Colorado River is overallocated,” Glennon told me over the phone last week. Glennon explained that the original Colorado River compact of 1922, which governs how seven states and Mexico use the river, was negotiated during “the wettest 10-year period in the last 1,000 years.” That law portioned out about 25 percent more water than regularly flows, so even in “normal” years, big reservoirs like Lake Mead are in a long-term decline. “We’ve been saved from the disaster because Arizona and these other states were not using all their water,” Glennon said.

They are now. Since around 2000, Arizona has been withdrawing its full allotment from the Colorado River, and it’s impossible to overstate how important the Colorado has become to the state. About 40 percent of Arizona’s water comes from the Colorado, and state officials partially attribute a nearly 20-fold increase in the state’s economy over the last 50 years to increased access to the river.

On April 22, Arizona held a public meeting to prepare for an eventual shortage declaration, which could come as soon as this August. The latest rules that govern a shortage, established in 2007 by an agreement among the states, say that Arizona will have to contend with a 20 percent cut in water in 2016 should Lake Mead fall below 1,075 feet, which will decrease the amount available to central Arizona’s farmers by about half. At 1,050 feet, central Arizona’s farmers will take a three-quarters cut in water. At 1,025 feet, agriculture would have to make due largely without water from the Colorado River. That would probably require at least a temporary end to large-scale farming in central Arizona. Below 1,025 feet, the only thing Colorado River states have agreed to so far is a further round of negotiations. In that emergency scenario, no one really knows what might happen. More

 

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