The upper Colorado River Basin is now experiencing a severe drought. A new study published in Geophysical Research Letters by federal government and university experts lead by the Bureau of Reclamation identifies a second-century drought that is more severe than the present drought or prior droughts.
“Previous studies have been limited to the past 1,200 years,” said Subhrendu Gangopadhyay, lead author and principal engineer for the Bureau of Reclamation’s Water Resources Engineering and Management Group. “However, a limited number of paleo records of moisture fluctuation date back 2,000 years.”
“While research has shown extended dry periods in the southwest dating back to the eighth century, this reconstruction of the Colorado River goes back about 800 years.”
According to the study, the water flow over a 22-year period in the second century was substantially lower, at only 68 percent of the average water flow, compared to the current 22-year drought in the Colorado River, which has only 84 percent of the typical water flow.
“Tree-ring records back to the second century are limited,” said Connie Woodhouse, a University of Arizona professor and research co-author. “However, paleoclimatic data from lakes, bogs, and caves describe this catastrophic drought event.”
To come up with these conclusions, the scientists rebuilt the streamflow at Lees Ferry on the Colorado River. The reconstruction’s paleoclimatic data comes from a gridded network of Palmer Drought Severity Index values based on tree rings. Water managers can use these long records to see if droughts in the distant past were similar to or worse than droughts seen in recent decades. The natural flow estimates collected from the Lees Ferry gauge from 1906 to 2021 are used as the study’s baseline.
The public can now access the reconstructed streamflow data obtained in this study. Water managers are expected to use this new extended data to better understand past droughts and plan for future droughts.
“The findings of this study can help water managers better comprehend the extent of flow variability in the Colorado River,” Gangopadhyay said. “It should provide knowledge to help water managers plan for droughts that are even more protracted and severe than previously thought,” says the report.
“Collecting and analysing more relic wood for future work can further chronicle this second-century drought,” Woodhouse noted.
A severe drought has gripped the Colorado River basin for the past 22 years, wreaking havoc across the West. This involves everything from drinking water to growing crops to generating electricity to power all we do. Drought has an effect on everything in the basin.
