The West’s Great River Hits Its Limits: Will the #ColoradoRiver Run Dry? — Yale360 #COriver #aridification

Grand River Ditch

Here’s Part I of a series about the Colorado River from Jim Robbins writing for Yale360. Click through and read the whole article (and enjoy the beautiful photographs). Here’s an excerpt:

As the Southwest faces rapid growth and unrelenting drought, the Colorado River is in crisis, with too many demands on its diminishing flow. Now those who depend on the river must confront the hard reality that their supply of Colorado water may be cut off.

The Never Summer Mountains tower over the the valley to the west. Cut across the face of these glacier-etched peaks is the Grand Ditch, an incision visible just above the timber line. The ditch collects water as the snow melts and, because it is higher in elevation than La Poudre Pass, funnels it 14 miles back across the Continental Divide, where it empties it into the headwaters of the Cache La Poudre River, which flows on to alfalfa and row crop farmers in eastern Colorado. Hand dug in the late 19th century with shovels and picks by Japanese crews, it was the first trans-basin diversion of the Colorado.

Many more trans-basin diversions of water from the west side of the divide to the east would follow. That’s because 80 percent of the water that falls as snow in the Rockies here drains to the west, while 80 percent of the population resides on the east side of the divide.

The Colorado River gathers momentum in western Colorado, sea-green and picking up a good deal of steam in its confluence with the Fraser, Eagle, and Gunnison rivers. As it leaves Colorado and flows through Utah, it joins forces with the Green River, a major tributary, which has its origins in the dwindling glaciers atop Wyoming’s Wind River Mountains, the second largest glacier field in the lower 48 states.

The now sediment-laden Colorado (“too thick to drink, too thin to plow” was the adage about such rivers) gets reddish here, and earns its name – Colorado means “reddish.” It heads in a southwestern direction through the slick rock of Utah and northern Arizona, including its spectacular run through the nearly 280-mile-long Grand Canyon, and then on to Las Vegas where it makes a sharp turn south, first forming the border of Nevada and Arizona and then the border of California and Arizona until it reaches the Mexican border. There the Morelos Dam — half of it in Mexico and half in the United States — captures the last drops of the Colorado’s flow, and sends it off to Mexican farmers to irrigate alfalfa, cotton, and asparagus, and to supply Mexicali, Tecate, and other cities and towns with water.

While there are verdant farm fields south of the border here, it comes at a cost. The expansive Colorado River Delta — once a bird- and wildlife-rich oasis nourished by the river that Aldo Leopold described as a land of “a hundred green lagoons” — goes begging for water. And there is not a drop left to flow to the historic finish line at the Gulf of California, into which, long ago, the Colorado used to empty.

Credit: Wikipedia.org

Nature, in fact, has been given short shrift all along the 1,450-mile-long Colorado. In order to support human life in the desert and near-desert through which it runs, the river is one of the most heavily engineered waterways in the world. Along its route, water is stored and siphoned, routed and piped, with a multi-billion dollar plumbing system — a “Cadillac Desert,” as Marc Reisner put it in the title of his landmark 1986 book. There are 15 large dams on the main stem of the river, and hundreds more on the tributaries.

The era of tapping the Colorado River, though, is coming to a close. This muddy river is one of the most contentious in the country — and growing more so by the day. It serves some 40 million people, and far more of its water is promised to users than flows between its banks — even in the best water years. And millions more people are projected to be added to the population served by the Colorado by 2050.

The hard lesson being learned is that even with the Colorado’s elaborate plumbing system, nature cannot be defied. If the over-allocation of the river weren’t problem enough, its best flow years appear to be behind it. The Colorado River Basin has been locked in the grip of a nearly unrelenting drought since 2000, and the two great water savings accounts on the river — Lake Mead and Lake Powell — are at all-time lows. An officially announced crisis could be at hand in the coming months…

Most of the water in the Colorado comes from snow that falls in the Rockies and is slowly released, a natural reservoir that disperses its bounty gradually, over months. But since 2000, the Colorado River Basin has been locked in what experts say is a long-term drought exacerbated by climate change, the most severe drought in the last 1,250 years, tree ring data shows. Snowfall since 2000 has been sketchy — last year it was just two-thirds of normal, tied for its record low. With warmer temperatures, more of the precipitation arrives as rain, which quickly runs off rather than being stored as mountain snow. Many water experts are deeply worried about the growing shortage of water from this combination of over-allocation and diminishing supply.

There is tree ring data to show that multi-decadal mega-droughts have occurred before, one that lasted, during Roman Empire times, for more than half a century. The term drought, though, implies that someday the water shortage will be over. Some scientists believe a long-term, climate change-driven aridification may be taking place, a permanent drying of the West. That renders the uncertainty of water flow in the Colorado off the charts. While not ruling out all hope, experts have abandoned terms like “concerned” and “worrisome” and routinely use words like “dire” and “scary.”

“These conditions could mean a hell of a lot less water in the river,” said Jonathan Overpeck, an interdisciplinary climate scientist at the University of Michigan who has extensively studied the impacts of climate on the flow of the Colorado. “We’ve seen declines in flow of 20 percent, but it could get up to 50 percent or worse later in this century.”

Even in rock-ribbed conservative areas, those who use the water of the Colorado say they are already seeing things they have never seen before — this year state officials in Colorado cut off lower-priority irrigators on the Yampa River, a tributary of the Green, and recreation had to be halted, for example — and have grudgingly come to believe “there is something going on with the climate.”

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