Saturday, August 8, 2020

What humpback chub means for future of Colorado River water supply

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Since the gates of Glen Canyon Dam were closed in 1963, the ecology of the Colorado River in the Grand Canyon has been altered, some fear forever.

Arizona Republic

Charismatic is hardly the best word to describe the humpback chub, a fish with a frowny eel face jammed onto a sportfish body in a way that suggests evolution has a sense of humor. Nor did tastiness build a fan base for this “trash fish” across its natural habitat throughout the Colorado River Basin. But, in 1973, the humpback chub became famous by winning federal protection under the Endangered Species Act.

Researchers in the Grand Canyon now spend weeks at a time, several times a year, monitoring humpback chub, which has become central to an ecosystem science program with implications for millions of westerners who rely on Colorado River water.

Dennis Harris, who guides an electrofishing boat for a research contractor, is part of the science crew that briefed me last year at the world’s largest known humpback chub hangout, just below the confluence of the Little Colorado River with the Colorado in Arizona. He spun a yarn about what fish say upon their return to home waters—how they survived an alien abduction.

“They scooped me up in a net and took me to the Mother Ship and stuck me with a piece of glass and probed my genitals and brought me back here,'” Harris said, throwing his head back and splaying his arms to imitate fish stunned by the electric current.

“And all their friends go, ‘Yeah, right.'”

The U.S. Geological Survey’s Grand Canyon Research and Monitoring Center runs three scientific trips each year to keep track of humpback chub and other fish species. Here, Clay Nelson is using a floodlight to find stunned fish and retrieve them at a sampling site on the main Colorado downstream from the Little Colorado River. Scientific findings are being used to help guide Colorado River operations. (Photo: Judy Fahys/InsideClimate News)

Funny as that sounds, the humpback chub’s experience is surprisingly meaningful now, as its river habitat deep in the iconic, redrock canyon becomes the subject of new scrutiny. New negotiations about the Colorado’s future begin later this year in a world that has fundamentally changed since foundational water agreements were drawn up, back when the river was flush and the entire basin was treated like a giant network of irrigation ditches.

Now, nearly a century after the original Colorado River Compact was forged, river stakeholders also find themselves in alien terrain as they try to reconcile an old management scheme with new realities, such as tribal rights, environmental protection and, especially, climate change.

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‘The pie is getting smaller’

About 40 million people in seven states and Mexico rely on the Colorado for irrigation, drinking and even hydropower. Most of the water is used in agriculture to irrigate more than 5.5 million acres.

Meanwhile, the Colorado is shrinking. Average river flows have dropped 19 percent over the last century. About half of the decline is blamed on global warming, and scientists project that unchecked climate change could nearly triple flow reductions by the century’s end. Meanwhile, basin tribes want to tap into allocations they haven’t been able to use because they lack means to store and pipe the water.

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