Science & Tech · Science & Environment · 3 hrs ago
Colorado River’s worst drought occurred during a cool period
Tree rings show the Colorado River’s worst drought came during a cool period about 2,000 years ago.
Researchers used samples from 199 bristlecone pines in southern Colorado to reconstruct summer night temperatures from 600 BCE to 2022.
The drought in the second century included two dry periods lasting 66 and 16 years, and the river’s flow was about 20% below levels during the current drought.
Cool droughts were nearly as common as warm ones over the full record, and both types lasted about 15 years on average.
The researchers found that cool droughts reduced river water by about as much per year as warm droughts, and slightly more by their measure.
Heat can worsen water shortages, but it is not required for a severe drought to develop.
The findings show that a long lack of rain and snow can cause extreme shortages, while today’s unusually warm summer nights add to the risk.
A tree-ring study found that the Colorado River’s deepest and longest drought in 2,000 years occurred during a cool period.
The drought took place in the second century, when summer nights in the river’s headwaters stayed cooler than average.
Researchers reconstructed summer night temperatures from 199 bristlecone pines, covering 600 BCE to 2022.
Across the two millennia, the study counted 34 warm drought periods and 27 cool ones, with both lasting about 15 years on average.
The findings indicate that a prolonged lack of rain and snow can cause severe water shortages even without unusual heat.
- Who
- Researchers led by Alexandre Nolin of the University of Arizona, with Connie Woodhouse and Cody Routson.
- What
- A tree-ring study found that the Colorado River’s longest and most severe drought in 2,000 years occurred during a cool period.
- When
- The drought occurred in the second century. The temperature reconstruction covers 600 BCE to 2022.
- Where
- The Colorado River’s headwaters in southern Colorado.
- Why
- The study examined how summer night temperatures related to drought. It found that long periods with little rain and snow can cause extreme water shortages even without unusual heat.
This story does not have two clearly opposing sides.
The researchers reconstructed year-by-year summer minimum temperatures from bristlecone pine rings.
The Colorado River experienced its longest and most severe drought in the 2,000-year record, during a cool period.
Earth.com published an account of the study’s findings.
- Tree-ring samples
- 199 bristlecone pines
- Temperature record
- 600 BCE to 2022
- Second-century drought
- Two drought periods lasting 66 and 16 years
- Missing water
- About five times the full capacity of Lake Mead
- Drought periods
- 34 warm and 27 cool periods
- Average duration
- About 15 years for both warm and cool droughts