New study finds severe drought impacting the upper Colorado River as far back as the 2nd century

Colorado River, photo by Roselie from Pixabay, St. George News

DENVER – The drought currently impacting the upper Colorado River Basin is extremely severe, according to a new study from the federal government and university scientists led by the Bureau of Reclamation and published in Geophysical Research Letters

The Colorado River below Glen Canyon Dam before Lees Ferry. A new study has found that the Colorado River experienced a severe drought impacting the Upper Colorado River Basin in the second century | Photo by Alex Stephens, Bureau of Reclamation, St. George News

The study identifies a second-century drought unmatched in severity by the current drought or previously identified droughts, according to a news release from the Bureau of Reclamation.

“Previous studies have been limited to the past 1,200 years, but a limited number of paleo records of moisture variability date back 2,000 years,” said Subhrendu Gangopadhyay, lead author and principal engineer for the Water Resources Engineering and Management Group at the Bureau of Reclamation. “While there has been research showing extended dry periods in the southwest back to the eighth century, this reconstruction of the Colorado River extends nearly 800 years further into the past.”

The research finds that compared with the current 22-year drought in the Colorado River, with only 84% of the average water flow, the water flow during a 22-year period in the second century was much lower, just 68% of the average water flow, the news release states.

“Tree-ring records are sparse back to the second century,” said Connie Woodhouse, a professor at the University of Arizona and a study co-author. “However, this extreme drought event is also documented in paleoclimatic data from lakes, bogs, and caves.”

FILE – In this Nov. 19, 2012, file photo, water is released into the Colorado River at the Glen Canyon Dam in Page, Ariz. The elevation of Lake Powell fell below 3,525 feet (1,075 meters), a record low that surpasses a critical threshold at which officials have long warned signals their ability to general hydropower is in jeopardy | Photo by Rob Schumacher/The Arizona Republic via AP, File, St. George News

The authors reconstructed the streamflow at Lees Ferry on the Colorado River to develop these findings. Paleoclimatic data for the reconstruction is from a gridded network of tree-ring-based Palmer Drought Severity Index values. These extended records inform water managers whether droughts in the distant past were similar to or more severe than observed droughts in the past centuries. The baseline for the study’s analysis uses the natural flow estimates data from 1906 to 2021 from the Lees Ferry gage.

What’s next?

The reconstructed streamflow data developed in this research is now available for public use. It is anticipated that water managers will use this new extended data to understand past droughts better and to plan for future droughts.

“The results of this work can provide water managers with an increased understanding of the range of flow variability in the Colorado River,” Gangopadhyay said in the news release. “It should provide information to help water managers plan for even more persistent and severe droughts than previously considered.”

Added Woodhouse:”For future work, collection and analysis of more remnant wood can further document this second-century drought.”

The Colorado River basin is experiencing a severe 22-year drought with extensive impacts throughout the West. This includes water for homes and crops to the generation of electricity that supports everything we do. Drought impacts everything within the basin.

Click here to learn more about the operations on the Colorado River.

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