#ColoradoRiver: “Unprecedented high temperatures in the [#COriver] basin are causing the flow of the river to decline” — Brad Udall

The Colorado River Basin. The Upper Colorado River Basin is outlined in black.
The Colorado River Basin. The Upper Colorado River Basin is outlined in black.

From The Las Vegas Desert Sun (Ian James):

Lake Mead reached the new all-time low on [May 18, 2016] night, slipping below a previous record set in June 2015.

The downward march of the reservoir near Las Vegas reflects enormous strains on the over-allocated Colorado River. Its flows have decreased during 16 years of drought, and climate change is adding to the stresses on the river.

As the levels of Lake Mead continue to fall, the odds are increasing for the federal government to declare a shortage in 2018, a step that would trigger cutbacks in the amounts flowing from the reservoir to Arizona and Nevada. With that threshold looming, political pressures are building for California, Arizona and Nevada to reach an agreement to share in the cutbacks in order to avert an even more severe shortage.

“This problem is not going away and it is likely to get worse, perhaps far worse, as climate change unfolds,” said Brad Udall, a senior water and climate research scientist at Colorado State University. “Unprecedented high temperatures in the basin are causing the flow of the river to decline. The good news is that we have time and the smarts to manage this, if all the states work together.”

[…]

As of [May 19, 2016], the lake’s level stood at an elevation of about 1,074.6 feet. The federal Bureau of Reclamation, which manages the reservoir and Hoover Dam, projects the level to decline a few feet more to an elevation of about 1,071 feet by the end of June, before the level begins to rise again with releases of water from Lake Powell.

Under the federal guidelines that govern reservoir operations, the Interior Department would declare a shortage if Lake Mead’s level is projected to be below 1,075 feet as of the start of the following year. In its most recent projections, the Bureau of Reclamation calculated the odds of a shortage at 10 percent in 2017, while a higher likelihood – 59 percent – at the start of 2018.

But those estimates will likely change when the bureau releases a new study in August. Rose Davis, a public affairs officer for the Bureau of Reclamation, said if that study indicates the lake’s level is going to be below the threshold as of Dec. 31, a shortage would be declared for 2017.

That would lead to significant cutbacks for Arizona and Nevada. California, which holds the most privileged rights to water from the Colorado River, would not face reductions until the reservoir hits a lower trigger point.

Representatives of California, Arizona and Nevada said last month that they hope to have a deal finalized by the end of the year for all three states to accept cutbacks earlier than otherwise required in order to head off a more serious crisis.

Interior Secretary Sally Jewell has said she is optimistic about the talks, calling the over-allocation of the river a shared problem that must be solved. During a May 4 visit to Southern California, she said that there has been “extraordinary collaboration” between the states in working toward a deal, and that the United States and Mexico have also been making progress in negotiations on a new accord to share water from the Colorado River.

While representatives of the three states have discussed the outlines of proposals to temporarily take less water from Lake Mead, they say considerable hurdles remain, including negotiations between water districts within each state…

Scientists have estimated that rising temperatures and the resulting declines in runoff across the Colorado River Basin could reduce the river’s flow by between 5 percent and 35 percent by the middle of the century.

“Human-caused climate warming will drive larger and larger flow reductions as long as emissions of greenhouse gases continue,” said Jonathan Overpeck, co-director of the University of Arizona’s Institute of the Environment.

“The river is over-allocated even before climate change is factored in,” Overpeck said in an email. He said he thinks the negotiations will probably “focus on how to reduce the over-allocation, but will eventually have to focus on sharing the pain as climate change continues to reduce the flows.”

From Esquire Magazine (Charles P. Pierce):

The long-term prognostications are just uncertain enough to be terrifying. The American Southwest—and the Los Angeles area in particular—are natural deserts. Only the miracle of engineering has made them habitable. Quite simply, we created human space in a place that, left to its own devices, would have been suitable only by cactus and lizards.

Often when we think we’ve conquered nature, we find we’ve only held it to a tenuous draw.

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