New Study Finds Extreme, Severe Drought Impacting the Upper Colorado River Basin in the Second Century

[System inertia, perhaps. Thermal inertia? Oy.~cr]

New study will help inform understanding of natural climate variability and assist the evaluation of the current drought compared to history

Peer-Reviewed Publication


Colorado River near Lees Ferry

DENVER – The drought currently impacting the upper Colorado River Basin is extremely severe. A new study from federal government and university scientists led by the Bureau of Reclamation and published in Geophysical Research Letters identifies a second-century drought unmatched in severity by the current drought or previously identified droughts.

“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 to 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. 

“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.”

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,” added Gangopadhyay. “It should provide information to help water managers plan for even more persistent and severe droughts than previously considered.” 

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

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.

Study co-authors also include Greg McCabe of the U.S. Geological Survey, Cody Routson from Northern Arizona University, and Dave Meko of the University of Arizona.

Reclamation continues to work with its partners to mitigate the impacts of this current 22-year drought. To learn more about the operations on the Colorado River, please visit


Geophysical Research Letters




Data/statistical analysis


Not applicable


Tree Rings Reveal Unmatched 2nd Century Drought in the Colorado River Basin



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Tom Halla
June 10, 2022 6:07 am

I would accept tree rings as drought indicators much more than as indications of temperature.

Frank from NoVA
Reply to  Tom Halla
June 10, 2022 8:11 am

Yes, but with the caveat that the tree ring data originates from the same drought-affected region, i.e., not cherry picked from, say, the Urals.

James Walter
Reply to  Tom Halla
June 10, 2022 11:24 am

Depends on the location. In drought prone areas, then drought for sure. But in non drought prone areas, temperature seems more logical.

Frank from NoVA
Reply to  James Walter
June 10, 2022 11:41 am

‘But in non drought prone areas, temperature seems more logical.’

I would easily concede that the width of an annual tree ring is contingent upon a specific tree’s available resources such as soil moisture, nutrients and sunlight (crowding), but temperature is a bridge way too far. ‘Temperature’ is where the ‘Dendros’ have to tease out spurious correlations with width, and where those of questionable integrity fall back on cherry-picking in order avail themselves of CAGW funding.

Tim Gorman
Reply to  James Walter
June 10, 2022 3:52 pm

Tree rings depend on far more than just temperature, even in wet conditions. Density of the trees changes the shading value which impacts growth. Insect infestations can impact tree ring width and can be difficult to even detect let alone quantify.

It’s all a crap shoot, even for drought identification. Take it all with a grain of salt, much of the interpretations are just guesswork, even from the experts.

Reply to  Tim Gorman
June 11, 2022 12:06 pm

Well, you can determine some things about temperature from a tree ring – when cold is prolonged, the cell structure is different. But it takes the equivalent of “a year without a summer” or more severe. So, yes, about all you can legitimately say about a year from a tree ring is “growing conditions good, growing conditions not so good.”

Len Werner
June 10, 2022 6:20 am

Since when has 70 to 80% of the recorded average snowpack come to invite the rhetoric ‘severe drought’? I have enjoyed Lake Powell so have enough interest to follow the Colorado snow data; both last winter and the one before the snow water equivalent figures were around that range. 70 to 80% of average is not ‘severe drought’.

Just because there’s not enough for all the straws sucking water out of the system does not mean the climate is broken; it just means there isn’t enough water for all the human activity that wants some. We’ll never solve that problem by trying to ‘fix the climate’.

‘If you don’t properly identify the problem, don’t expect to arrive at the correct solution’.

Steve Case
Reply to  Len Werner
June 10, 2022 6:59 am

‘If you don’t properly identify the problem, don’t expect to arrive at the correct solution’.

‘If there isn’t a problem, you don’t need a solution’.

alastair gray
Reply to  Steve Case
June 10, 2022 1:46 pm

The article mentioned a flow volume of 84 % of average. close to Len Werner’s 70 -80% snowpack figure. so what is the criterion for severe drought. I tend to think of dried up wadis where formerly rovers flowed as severe drought. Illuminate me someone please

Reply to  Len Werner
June 10, 2022 7:03 am

Correct – when you look at how much population and development have increased in California, Arizona, and Nevada over the last 50 years, or even the last 20 years, it’s clear that the problem is not insufficient flow but excessive draw.

Of course, the great majority of “consumptive” water use has been agriculture and maintenance of urban and suburban landscaping. Actual water use for drinking, bathing, sanitation, laundry and cooking is tiny compared to water used in irrigation.

I don’t know the extent to which the southwestern states have adopted “recycled” wastewater for landscape irrigation, but that is the norm here in Florida, which despite getting lots of precipitation, we can’t store it in snowpack and large reservoirs due to our flat terrain, so water conservation has been a very big deal here for decades. The Tampa Bay area also has been using desalinated salt water for decades to reduce groundwater draws.

The state and local governments in the southwestern US could easily reduce much of their current demand by limiting landscape irrigation – such as by switching to native xeriscape plants instead of imported grass lawns and trees. But the governments don’t want to annoy their voters, so they simply blame the environment and global warming, which make convenient scapegoats for their overconsumption. The American southwest is primarily a desert, always has been, and attempting to make it as green as the eastern states is the problem.

Last edited 2 months ago by Duane
Old Man Winter
Reply to  Duane
June 10, 2022 8:07 am

Since 1960, the Colorado’s been very low/dry going into the Gulf of California.

Richard Patton
Reply to  Old Man Winter
June 10, 2022 9:14 am

Don’t blame U.S. farmers/consumers for that. Blame Mexico. Three miles west of Yuma, AZ. at the first point that Mexico can access the water from Colorado, they divert 90% of the flow for their purposes. Ten miles further downstream the Colorado is a dried river bed. See this Google aerial view:

Reply to  Old Man Winter
June 10, 2022 11:29 am

I don’t know how much exactly, but a lot of Pacific drainage water is diverted through tunnels to the Front Range, east of the divide and part of the Gulf of Mexico drainage.

Reply to  Duane
June 10, 2022 11:10 am

Keep in mind now 20% of the Colorado water now ends up in the Denver area also.

Reply to  mal
June 10, 2022 11:30 am

I just saw your comment. Made a similar one.

Reply to  mal
June 10, 2022 12:04 pm

It’s not nearly that high. Denver collects a total of 290 thousand ac-ft per year, about half of which (150 thousand) comes from the Colorado River. The river’s flows are divided half and half between the upper basin (north of Arizona) and the lower basin (AR, CA, and NV) – at 7.5 million ac ft each or 15 million ac-ft per year total. So Denver’s share of the total Colorado River flow is only 1% of the total river flow.

California receives about 20% of the Colorado River’s flow, or 3 million ac-ft per year. Arizona gets another 2.8 million ac-ft.

Romeo Rachi
Reply to  Duane
June 14, 2022 1:49 pm

Of the upper basin draw, I believe Colorado takes roughly 60 percent of that. Arizona takes the least at only 50,000 acre feet. So, Denver does take a lions share as well. After all, they are growing just as fast as Phoenix and Vegas.

Citizen Smith
Reply to  Len Werner
June 10, 2022 7:37 am

What comes after extreme-severe drought?

Reply to  Len Werner
June 10, 2022 9:13 am

Not just severe, it is “extremely severe”!!!!!!!! I’ve been wondering what superlatives we can use after “extreme drought, extreme weather, etc.”

Reply to  Pflashgordon
June 10, 2022 10:38 am

“Exceptional” is the word the drought monitor uses, although that actually sounds less impressive to me than “extreme”. Maybe they should reverse the terms.

Last edited 2 months ago by beng135
June 10, 2022 6:30 am

“Tree-ring records are sparse back to the second century,””

Who can help Connie Woodhouse out?

Step forward Michael Mann, climate hero, Nobel chaser and general whinge-bag.

Andrew Kerber
June 10, 2022 6:43 am

There is a reason this is called the great American desert.

lee riffee
Reply to  Andrew Kerber
June 10, 2022 7:46 am

Exactly….Makes me wonder what on earth do people expect when they are living in a desert and depending on water from elsewhere. And then to blame “climate change” when you run low (or run out) of water in said desert!

June 10, 2022 7:22 am

Is there an analog with Great Plains soil data?

Old Man Winter
June 10, 2022 7:34 am

According to these- in much wetter Europe- sea water extended above London Bridge even at ebb
tide, the Danube could be “passed over dry-footed”, the Seine and Loire were as dry land, & the Rhine dried up. So this shouldn’t be a big surprise either!

The graph below shows extended droughts were quite common 1k yrs ago in the US West-

Reply to  Old Man Winter
June 10, 2022 10:39 am

Here is that Cook et al. 2007 publication.

And here is the original graph as it appears in the publication.

comment image

Note that this graphic is for PDSI < -1 up to 2003 and for the western region. For periods after 2003 (not included in the graphic) we see that the area covered by USDM D0+ (the same as PDSI < -1) is now over 90%. And over the last 20 years it has averaged 63% [1]. According to Cook et al. 2007 the graph has 60 yr smoothing. And the last 60 years up to 2022 is now at or even exceeding 50% eclipsing the 850-1050 drought and not far off from the peak around 1150.

Last edited 2 months ago by bdgwx
June 10, 2022 7:39 am

This is interesting. The 1906-2021 mean flow in the Colorado River is 18 bcm as compared to the 2000-2021 mean flow of 15 bcm with 2001 getting down to 10 bcm. But in the 2nd century annual mean flows remained as low as 10 bcm for many years consecutively. Given the precedence of previous megadroughts in this publication in conjunction with increasingly higher water consumption rates today it would be unwise to scoff at the possibility of more extreme water shortages in the area than are already occurring.

Last edited 2 months ago by bdgwx
Reply to  bdgwx
June 10, 2022 9:02 am

Nobody is scoffing at the possibility of more severe drought.
We are scoffing at two things.
First, the frequent claim that the current drought is utterly unprecedented and
Second, the claim that the current drought could only have been caused by CO2.

Reply to  bdgwx
June 10, 2022 9:34 am


The takeaway is that as more research is done about climate events during the Holocene, the more we learn we have been here before. The media narrative is irresponsible, ignorant and insane. I’m speaking of every aspect of climate, not just droughts.

Reply to  cerescokid
June 11, 2022 5:58 am

cerescokid: “The media narrative is irresponsible, ignorant and insane. ”

Not to mention bought and paid for to guarantee they are onside.

The few in the various media who actually have a bit of clue dare not even suggest anything but the climate porn du jour if they want to remain employed.

The best way to get cancelled, become unemployed and unemployable in the legacy media is to swerve outside of the climate alarm lane, even just once.

June 10, 2022 8:13 am

This is what makes the study of climate interesting.
A big drought in the Western US in the 2nd century. This is apparently due to the climate swinging colder, the Roman Empire largely collapsed and Europe went into the Dark Ages with crop failures, famine and Plague.
Then the desert Southwest had a big drought centered around 1200 AD, corresponding to the Medieval Warm Period.

drought cold
drought warm

Go figure.

Reply to  TonyL
June 10, 2022 11:54 am

1200 AD being about when the Anasazi abandoned Mesa Verde, because of…drought. Yawn.

June 10, 2022 8:18 am

The more people they import the less resources for US citizens. The impact is in all areas.

Reply to  Olen
June 10, 2022 9:20 am

If the lunatic fringe want to cut greenhouse gases in the U.S., they should close the border and deport all illegals. The single biggest factor in increased consumption, combustion and (as if I care) human-induced greenhouse gas emissions is population growth.

Peta of Newark
June 10, 2022 9:48 am

So what. Birds can fly and fish can swim, some of us could have guessed that.

It’s an ancient desert with highly weathered ## and eroded soils, what did they expect to find?

From the Bureau of Reclamation as well. Lord help us.
What would be news news is when they live up to their name and actually do do some ‘reclamation‘ i.e Actually put some fertility into that dirt.
By then of course, the birds would be in aerial competition with pigs.

There again, ‘a bureau’ = ‘a desk’ – what good did sitting at a desk ever do?
From: Bureaucracy = The Rule of/by Desks

## NB ‘Weathered‘ and NOT ‘Climated

edit to PS
Any proper historians in the house? There’s the clue.
How long has it been ‘Colorado
i.e. Colorado = The Colour Red

Forests ain’t red.
Grasslands ain’t red
Lakes, rivers and streams/water isn’t red

So what was ‘The Colour Red’ referring to and for how long?

Last edited 2 months ago by Peta of Newark
Reply to  Peta of Newark
June 10, 2022 11:15 am

The water that ran through Arizona before the dams were red. If you wonder were the red comes from just look a the San Juan river after a rain storm. It looks like red cholate milk.

Reply to  Peta of Newark
June 10, 2022 11:48 am

To add to mal’s comment, there is a lot of red sandstone in Colorado. You can see examples of it in the following 10 minute video of a hike to one of the Flatirons of Boulder.

Reply to  Scissor
June 11, 2022 7:25 am

Let’s take up a collection and buy that poor fellow a pocket comb.

Patrick B
June 10, 2022 10:00 am

From the paper: “The second century occurs in the earliest part of the timespan covered by tree-ring data in the UCRB region. A total of 11 tree-ring chronologies in or near the UCRB extend into the second century (Table S4 in Supporting Information S1; Figure 4a).”

Am I reading this to mean they used 11 trees scatter through several States for the early part of this reconstruction?

Yes, I see they somehow used 37 non-tree ring indications to “support” their conclusions.

Look folks, I don’t mind agreeing those data suggest a drought. And I understand there may not be a lot of data to be had even if we searched more. But to take this and try to build model for river flow out of several States? Jesus Christ folks, talk about hanging on a thin reed.

James Walter
June 10, 2022 11:22 am

They make it sound like there is a solution. There is: don’t build in or take water from drought prone areas, don’t build on the fault line, don’t build on top of the coming land slide, don’t build in the flood prone areas, etc. There was a video of a guy who built or bought his house which sits on the top of a known land slide area. He said he didn’t care. The probability was low that it would happen in his lifetime.
Unfortunately, high risk, but high aesthetics is where the greatest profits are, and you know the golden rule: he who has the gold, makes the rules. The history of the evils of unregulated capitalism is conclusive. BTW, Labels are always wrong. “The map is not the territory. The word is not the thing.” Korzybski He also opposed the word “is” diminishing people to being only certain traits: He “is” much more than a father, singer, thief, killer, lover, soldier, accountant, etc.

Reply to  James Walter
June 10, 2022 1:15 pm

Re “you keep using that word but …” the complaint above is even faintly not about “capitalism” but about individual choice. Apparently James supports the Soviet fashion, a bureaucrat for every aspect of every individual life, which frequently boils down to ‘keep all the good stuff for ourselves’.

Last edited 2 months ago by AndyHce
June 10, 2022 11:58 am

How can you get past data from a water gage at Lee’s Ferry, which is 14 miles downstream from the modern dam that created Lake Powell? The dam controls the water flow all the way to theHover Dam.

Bill Parsons
Reply to
June 11, 2022 3:48 pm

Guessing, but…

comment image

Lower CFS flows expose relict (buried) wood tree samples in the mud. In French river reconstructions divers retrieve Roman and pre-Roman galleys and dugout skiffs from under the mud and the dendros reconstruct ages of wood just fine. If they’re buried in mud and kept moist the samples are preserved and rings are easy to count. As for bogs and other layered samples, I guess they have to find overflow areas or oxbows where silt builds up over milennia to take cores. Thicker deposition layers mean higher stream flows those years.

But as you suggest and the above chart proves, the modern river is no longer a reliable vector for determing “natural” deposition. It is manipulated by man and declining CFS just means there are more people upstream taking more water. Measuring its silt deposits is like measuring the level of a milk shake in a glass with 50 or so straws stuck in it and various people slurping it out. So how does the Woodhouse team (I can’t spell the other guy’s name) account for these man made deficits? (I didn’t see link to the actual paper.)

Tom Holsinger
June 10, 2022 5:13 pm

Actually this applies to the whole Southwest, including California. See:

The West without Water: What Past Floods, Droughts, and Other Climatic Clues Tell Us about Tomorrow, Ingram, B. Lynn, and Malamud-Roam, Frances, 2013, University of California Press

Bill Parsons
June 10, 2022 11:30 pm

Since the 30s, scores of dams have been built on the Colorado’s stem and upper river basins above Lee’s Ferry. They have a combined reservoir and diversion capacity somewhere north of 80 million acre feet. The researchers no doubt found evidence of severe drought in the past. But you have to wonder how data derived from deposition of silt in lakes or bogs or accretion of tree rings can reveal anything about current stream flow. Massive amounts of Colorado River water are drained from the system. Whatever Ms. Woodhouse et al observe about modern day river flow is based on what is released from the dams and what is allowed to pass downstream by us humans. The West’s drought-prone climate draws more people to it every year. A more productive study might be one on the changing U.S. demography and how much water is being used by agriculture.

Reply to  Bill Parsons
June 10, 2022 11:34 pm

Any data revealing the amount of water spent irrigating corn for ethanol would be welcomed.

Pat from kerbob
June 12, 2022 8:53 pm

Seems to be lots of moisture in that basin recently?
It’s been dry but that’s why it’s desert, it’s also why so many people move there, chasing heat and dry because humans hate cold and wet

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