Claim: Colorado River basin due for more frequent, intense hydroclimate events

Climate change will drive more drought, heat waves, floods, and low river flows in seven western states


Research News


LOS ALAMOS, N.M., April 6, 2021–In the vast Colorado River basin, climate change is driving extreme, interconnected events among earth-system elements such as weather and water. These events are becoming both more frequent and more intense and are best studied together, rather than in isolation, according to new research.

“We found that concurrent extreme hydroclimate events, such as high temperatures and unseasonable rain that quickly melt mountain snowpack to cause downstream floods, are projected to increase and intensify within several critical regions of the Colorado River basin,” said Katrina Bennett, a hydrologist at Los Alamos National Laboratory and lead author of the paper in the journal Water. “Concurrent extreme events of more than one kind, rather than isolated events of a single type, will be the ones that actually harm people, society, and the economy.”

Another example of concurrent hydroclimate events might be low precipitation accompanied by high temperatures, which cause drought as an impact. Other factors such as low soil moisture or wildfire burn scars on steep slopes contribute to impacts.

“You never have just a big precipitation event that causes a big flood,” Bennett said. “It results from a combination of impacts, such as fire, topography, and whether it was a wet or dry summer. That’s the way we need to start thinking about these events.”

The Los Alamos study looked heat waves, drought, flooding, and low flows in climate scenarios taken from six earth-system models for the entire Colorado River basin. The basin spans portions of Wyoming, Colorado, New Mexico, Utah, Nevada, Arizona, and California.

Using indicators such as maximum temperature, maximum precipitation, dry days, maximum and minimum streamflow, maximum and minimum soil moisture, and maximum evapotranspiration, the team ran the models for a historical period (1970-1999) and a projected future period (2070-2099). They studied the difference between the two periods (future minus historical) for events at four time scales: daily, monthly, seasonal, and annual.

Overall, precipitation across the Colorado increased by 2.1 millimeters between the future and historical periods, with some models showing increases in precipitation and some showing decreases. Nonetheless, the team found that in all cases, precipitation changes still drove an increase in concurrent extreme events.

Unsurprisingly, temperature increased across all six models and was an even stronger catalyst of events. Consistently across the entire basin, the study found an average temperature rise of 5.5 degrees Celsius between the future and historical periods.

In every scenario, the number and magnitude of each type of extreme event increased on average across the Colorado River Basin for the future period compared to the historical period. These numbers were given as a statistical expression of the change in frequency between the historical and future period, not as a count of discrete events.

Those increases have significant social, economic, and environmental implications for the entire region, which is a major economic engine for the United States. The study identified four critical watersheds in the Colorado basin–the Blue River basin, Uncompahgre, East Taylor, Salt/Verde watersheds–that are home to important water infrastructures, water resources, and hydrological research that would be particularly vulnerable to extreme events in the future.

More than 40 million people depend on the Colorado River basin for water, and it directly supports $1.4 trillion in agricultural and commercial activity–roughly one thirteenth of the U.S. economy, according to 2014 figures.

In Utah, Colorado, Arizona, and New Mexico, flooding, drought, freezing events, wildfire, severe storms, and winter storms have cost approximately $40 billion between 1980-2020.


The Paper: “Concurrent Changes in Extreme Hydroclimate Events in the Colorado River Basin,” Katrina E. Bennett (corresponding author), Carl Talsma, and Riccardo Boero, in Water 2021, 13, 978, April 1, 2021.

The Funding: This work was funded by the Early Career Laboratory Directed Research and Development (LDRD) program at Los Alamos National Laboratory.

About Los Alamos National Laboratory

Los Alamos National Laboratory, a multidisciplinary research institution engaged in strategic science on behalf of national security, is managed by Triad, a public service oriented, national security science organization equally owned by its three founding members: Battelle Memorial Institute (Battelle), the Texas A&M University System (TAMUS), and the Regents of the University of California (UC) for the Department of Energy’s National Nuclear Security Administration.

Los Alamos enhances national security by ensuring the safety and reliability of the U.S. nuclear stockpile, developing technologies to reduce threats from weapons of mass destruction, and solving problems related to energy, environment, infrastructure, health, and global security concerns.


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Carlo, Monte
April 8, 2021 6:09 pm

How did they extract a tenth of a millimeter of precipitation from their soothsaying?

Do these people not understand the terms “semi-arid” and “desert”?

Reply to  Carlo, Monte
April 8, 2021 6:45 pm

Looks like I’ll have to add another slide to the 97% Collusion report …

Joel O'Bryan
Reply to  Carlo, Monte
April 8, 2021 9:07 pm

Simple: They employed State of the Art Climate Dowsing techniques to discern to sub-millimeter precision the precip changes from CO2 rise.
Similar to:

Screen Shot 2021-04-08 at 9.06.03 PM.png
Carlo, Monte
Reply to  Joel O'Bryan
April 9, 2021 7:31 am

A digital dowser, now I’m impressed.

Reply to  Joel O'Bryan
April 9, 2021 10:56 am

Do not disparage dowsing (I was a disbeliever until I actually did it) it is more real than this claptrap from Los Alamos.

How far have they sunk? Was it when Hazel O’Leary decided that color-coded security badges were RACIST?

Reply to  Kpar
April 10, 2021 4:59 pm

My experience, also.

Reply to  Joel O'Bryan
April 10, 2021 12:30 pm

“he Los Alamos study looked heat waves, drought, flooding, and low flows in climate scenarios taken from six earth-system models for the entire Colorado River basin. The basin spans portions of Wyoming, Colorado, New Mexico, Utah, Nevada, Arizona, and California.

Forget using real data. Fantasyland stuff meets their desires better.

Using indicators such as maximum temperature, maximum precipitation, dry days, maximum and minimum streamflow, maximum and minimum soil moisture, and maximum evapotranspiration, the team ran the models for a historical period (1970-1999) and a projected future period (2070-2099). They studied the difference between the two periods (future minus historical) for events at four time scales: daily, monthly, seasonal, and annual.”

Oh! Not only fantasy future predictions, but they used models to fantasize historical event also…

All delusion, all of the time! True leftist demagoguery,

Reply to  Carlo, Monte
April 9, 2021 4:33 am

I re-ran the calculations myself and got 2.04651 mm.

Trying to Play Nice
Reply to  DHR
April 9, 2021 5:59 am

With a little help from Nick Stokes you might be able to take that out a few more decimal places.

paul courtney
Reply to  Trying to Play Nice
April 9, 2021 11:53 am

Mr. NIce: Yes, but only to reduce the uncertainty. /s/ again.

Reply to  Carlo, Monte
April 9, 2021 9:11 am

The average delta 2.1 (+/- 0.05) mm is across the time frame of ‘future & historical periods’.

It’ O.K. to be that precise when modeling. It may well be that ‘historical to present’ periods have increased by 8 mm; and the modeled ‘present to future’ change is a decrease of 5.9535 mm.

And per DHR below, the overall change from ‘the past’ to ‘sometime in the future’ will be 2.04651 mm.

But of course, depending on your rounding process the increase would then only be 2.0 (+/- 0.05) mm; but that’s o.k. too because they can state that they figured it out to within 5% … that’s a pretty good limit when dealing with such a time frame as ‘future & historical periods’.

Reply to  DonM
April 9, 2021 1:13 pm

and remember – all this is – “projected”; not even a prediction . . .
Para 2, first sentence.


Tombstone Gabby
Reply to  auto
April 9, 2021 5:53 pm

Hopefully, there’ll still be a few skeptics around in 2099 to say, “Another failed ‘projection'”.

No thoughts on what will happen between now and 2070? Any ‘projection’ this far out deserves the expression, “Far out, man”.

Reply to  DonM
April 10, 2021 12:36 pm

Read the modeling section…
They modeled past results as well as modeled future projections.

That is, a true battle of models; models for ancient against models for future times…

Maybe not next year or the year afterwards, but sometime somewhere their results may be repeated…

Tom Halla
April 8, 2021 6:10 pm

5.5 C warmer by 2070? It looks like they are using RCP 8.5, which Judith Curry classified as “borderline impossible”.

Joel O'Bryan
Reply to  Tom Halla
April 8, 2021 9:20 pm

(ding ding ding!!!!….) You win the Prize!!! Yes!!

Bennett et al write in para 2.2 of their manuscript:

“For this work, we used the representative concentration pathway (RCP) 8.5 emissions scenario, which tracks closely with changing emissions levels over time [62] and anticipates strongly increasing emissions by 2100 [63].”

Free access at:

Totally bogus paper because it uses a bogus forcing scenario. RCP 8.5 was devised for this very reason… to be a honey pot trap to lure in other discipline researchers and get them to ride the Climate Gravy train, because using extreme (albeit unrealistic) future scenarios is the only way to show significant future impacts to get that paper published. “Publish or perish” drives this nonsense.

Reply to  Joel O'Bryan
April 9, 2021 9:39 am

But Joel,

The ‘conflict of interest’ statement in the paper says:

Conflicts of Interest

The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.

(But then again, they did go out of their way to thank an anonymous reviewer for their “suggestions & improvements to the text” of the paper. This acknowledgement is right above the conflict of interest statement.)

Reply to  DonM
April 9, 2021 10:58 am

Nothing to see here, move along.

Reply to  DonM
April 10, 2021 12:43 pm

Screwy absurd model idea.
Screwy concept of pitting modeled history against modeled future projections.
Screwy validation methods.

anonymous reviewer” advising them.

Perhaps, Mannical is their “anonymous reviewer”!?

The best way to find out is that Manniacal is totally unable to resist tooting his own horn.
A little teasing and the dendro-fool tells all.

Robert of Texas
April 8, 2021 6:27 pm

What do they consider “extreme”? Houses get erased by a flood? (Predictable this will go up with higher population and dumb building codes) Or just floods in general? If it gets 1 degree warmer one week then it had in the past 100 years (for that corresponding week) is that extreme? Or is it just a Monte Carlo simulation being played by Mother Nature?

The 4-Corners area once received more rain, and then it got drier about when climate started cooling. It doesn’t take a soothsayer (or a computer model) to guess that a return to higher temperatures could mean more rain.

I know…I KNOW! It’s worse then we thought, everbody run about with their hair on fire, CO2 is EVIL. There, did I get the talking point correct?

Gary Ashe
Reply to  Robert of Texas
April 8, 2021 6:35 pm

The point is theres too much rain for hair fires silly.
Its kind of pissing on their parade.

Last edited 5 days ago by Gary Ashe
Carlo, Monte
Reply to  Robert of Texas
April 8, 2021 8:47 pm

All they had to do was visit Mesa Verde…

Reply to  Robert of Texas
April 9, 2021 9:24 am

The defined extreme as in the top 95 percentile.

April 8, 2021 6:29 pm

Where is my dart board?

Rick C
April 8, 2021 6:38 pm

Models = GIGO = BS

April 8, 2021 6:43 pm


April 8, 2021 7:09 pm

This is just….trivial. Climate change is trivial too compared to….the loss of the entire Solar System. Yes, it is in jeopardy from….Evil Anti-matter….once Anti-matter reaches the tipping point, an irreversible chain reaction cannot be stopped….it’s out there….just beyond Uranus.

Abolition Man
April 8, 2021 7:11 pm

I noticed they spent a lot of time talking about the ENSO fluctuations and how that will affect the Southwest monsoons!
Oh, wait, that would take actual work and data from real observations; it’s so much more fun to play around with models in the office and make stuff up! Isn’t that Harvey Weinstein’s old job description?

Pat from kerbob
April 8, 2021 7:19 pm

Since the USA has been cooling for decades when do they expect the warming to actually occur?

And a future increase of 2.1mm in one model is bad?

I just don’t get it

Steve Case
April 8, 2021 7:19 pm

From my file of quotes factoids and smart remarks:

If the Climate Change headline says, 
 “Worse than previously thought” 
Historical data has been re-written.

April 8, 2021 7:28 pm

IPCC’s AR5 Climate Report stated empirical data show no discernible global increasing trends in frequency nor intensity for 100 years for: hurricanes, typhoons, cyclones, thunderstorms, tornadoes, droughts, floods, and hail…

Empirical evidence does suggest there has been a slight increasing trend in global rain and snow, which makes sense as slightly warming global temperatures will generate more ocean evaporation leading to increased precipitation, but it certainly isn’t a “catastrophic” increasing trend.

CAGW cultists understand the PDO and AMO will soon reenter their respective 30-year cool cycles leading to falling global temperatures for 30+ years. Accordingly, CAGW cultists are frantically creating absurd catastrophic climate models to provide Leftist politicians with propaganda to justify spending $trillions on CAGW mitigation before the CAGW hypothesis is disconfirmed by multi-decadal cooling global temperatures.

We’ll see soon enough..

April 8, 2021 7:49 pm

Head for the Rockies and get your vaccinations if you want to join the queue of climate refugees for Oz-
‘Ghost forests’ are creeping along Eastern Coast in worrying sign of climate change (
Have you got enough solar powered helicopters to rescue the survivors clinging to the top of the Statue of Liberty?

Reply to  observa
April 8, 2021 8:37 pm

The moron that wrote the Ghost forest article was not bright enough to figure for a foot ocean rise in one area is more likely either. The land sinking rather the the ocean rising in one place. Land sinking generally do to a few causes on is recovery from glaciation one area rising another sinking due to the loss of the pressure of the ice during the last glacial event. Another to much pumping fresh water out from below. Yet another is a delta sinking because the river that feed it was channeled and not the slit just goes into the ocean. Since this is North Carolina my guess is it one of the last two.

Reply to  MAL
April 8, 2021 9:21 pm

It’s a constant barrage of drivel like that from the lamestream media. I think the advent of social media has a lot to do with it as the Fourth Estate struggles to rise above the chattering milieu and becomes just so much more doomster clickbait for an airheaded ADHD populace.

Reply to  MAL
April 10, 2021 12:55 pm

Without reading the drivel ghost forest stuff…

Most Eastern “ghost forests” are caused by excessive freshwater ground extraction that lowers the water table allowing salt water incursion.

For some odd reason a lot of the coastal areas are not near rivers and they never purchased land to build reservoirs. Instead, they just pumped their freshwater stores into lawns, swimming pools and toilets.
Gee, it must be climate change! /s

Last edited 3 days ago by ATheoK
April 8, 2021 8:05 pm

The spectacular American Indian ruins of Chaco Canyon and Mesa Verde national parks are in this region. They are testimony to rich agriculture societies centuries ago and populations that abandoned their dwellings due to multi-decade droughts. Climate change here, not unusual in the past and not related to changes in CO2.

Carlo, Monte
Reply to  RelPerm
April 8, 2021 8:50 pm

And these Los Alamos people are right next door to Chaco Canyon, sheesh.

Steve Keohane
April 8, 2021 8:09 pm

“You never have just a big precipitation event that causes a big flood,” Bennett said. “It results from a combination of impacts, such as fire, topography, and whether it was a wet or dry summer. That’s the way we need to start thinking about these events.””
BS, the Big Thompson Flood of 1976. A thunderstorm hung over Estes Park Colorado, dumped a foot of water resulting in a twenty foot wave of water going down the Big Thompson Canyon. 160+ deaths. The sigma for weather in Colorado is so enormous I wouldn’t count on any predictions. There has been talk of a drought here, here being five miles from the headwaters of the Colorado River. So I looked over my daily precip records for the past several years, no change. There has also been talk of snowpack melting earlier. I record when the ground clears of snowpack, again no change at my place.

Carlo, Monte
Reply to  Steve Keohane
April 8, 2021 8:55 pm

In 1904 just north of Pueblo Colo. 96 people died when an express train crashed into a gully where the railroad trestle had been taken out by a huge flash flood, no CO2:

Steve Keohane
Reply to  Steve Keohane
April 10, 2021 5:53 am

Here is the last dozen years of total water precipitation from 10/1-4/9 of the following year. I chose that start as it is the start of the water year. The second listing is the date for snow-free ground, ie. when the winter snowpack melts. It may snow after that date, but melts quickly.
2021, 8.93″, 3/28
2020, 9.46″, 3/29
2019, 15.15″, 4/7
2018, 8.33″, 3/16
2017, 8.90″, 3/18
2016, 9.25″, 3/27
2015, 8.35, 3/5
2014, 11.31″, 4/4
2013, 8.02″, 3/25
2012, 6.54″, 4/12
2011, 8.98″, 3/13
2010, 6.78″, 3/28
Ave water=8.92″ with 1 sigma=2.38″

April 8, 2021 8:51 pm

Overall, precipitation across the Colorado increased by 2.1 millimeters between the future and historical periods, with some models showing increases in precipitation and some showing decreases.”


That’s slightly greater than the thickness of a nickel or about 2 pennies. Grab your snorkel now!

K. McNeill
April 8, 2021 8:53 pm

I got as far as models then phsst.

April 8, 2021 9:23 pm

Those Los Alamos buffoons need to get back to making bombs.

James Walter
April 8, 2021 9:25 pm

They completely ignored the tree ring data which shows that frequent, long droughts, with only the occasional wet periods, is NORMAL, not caused by climate alarmism.

Steve Keohane
Reply to  James Walter
April 10, 2021 5:36 am

Gee, maybe there is a reason the area is referred to as the ‘desert south-west’.

April 8, 2021 11:00 pm

The Thames River Catchment has the best historic records of rainfalls and stream flow of any river in the world.
The Thames River Catchment is only 5000 sq miles and has varying terrain and soil types which make accurate comparison of todays flows with historic flows impossible.

The Colorado River Catchment is approximately 250,000 sq miles with sparse rainfall and flow records.

Any prediction of future flows without knowledge of past is laughable.

Climate believer
April 8, 2021 11:22 pm

“…are projected to increase and intensify…”

Yeah, let us know in 2099 how that worked out for you, I’m still waiting for a 5 day weather forecast that gets it right more than a coin toss. 

April 9, 2021 2:56 am

So, it could be a little or it could be a lot

Either way, it’s projected to be a catastrophe

Extreme nonsense

April 9, 2021 3:31 am

I see that they postulate that low precipitation accompanied by high temperature causes drought.
Well, well, who would have thought it?
I’m glad I’m not paying for the salaries of these nincompoops. I see that the work was funded by the Early Career Lab. Does that mean Kindergarten?

Jim Whelan
Reply to  Oldseadog
April 10, 2021 8:49 pm

I believe that only the low precipitations is needed. High temperatures accompany low precipitation because, you know, lack of evaporative cooling and clouds.

John Pickens
April 9, 2021 5:20 am

The most disastrous flood in Colorado recently was caused by EPA incompetence at the Gold King mine.

April 9, 2021 6:50 am

The Colorado river valley is pretty deep. That should be enough evidence in itself that flooding far in excess of their predictions has happened in the past….modern estimates of the “flood plain” are probably wishful thinking by land developers…..

Reply to  DMacKenzie
April 9, 2021 7:21 pm

The largest recorded flow is from 1920
The largest flow since European settlements was 1884
Sediment studies suggest 20 plus flows greater the 1920 but only one greater than 1884 in last 4500 years.
The Hoover dam was designed using the estimated flows from the 1884 flow.
There is no possible way to quantify the breakdown of snow melt with rainfall from the 1884 event or any other historic event.

This makes discussions about extra few mms totally useless.

Reply to  DMacKenzie
April 10, 2021 1:05 pm

The Colorado valley has been lifted to a high elevation.
That valley could have been cut when it used to be underwater.

Steve Z
April 9, 2021 8:19 am

It’s absolutely crazy to think that the climate will warm by 5.5 C (9.9 F) over the next 50 years in the Colorado River basin. Even if (for sake of argument) we believe the IPCC models with a climate sensitivity of 1.8 C per doubling of CO2, if CO2 levels at Mauna Loa continue to rise at (for example) 3 ppm per year, by 2070 the CO2 level will be at 560 ppm. On a logarithmic scale, that is equivalent to 0.45 doublings (560/410 = 2^0.45), or a temperature rise of 1.8 * 0.45 = 0.81 C. For the Los Alamos Lab to believe that the temperature rise in the Colorado basin would be nearly 7 times that predicted by the IPCC is absolutely ludicrous.

[QUOTE FROM ARTICLE] “Overall, precipitation across the Colorado increased by 2.1 millimeters between the future and historical periods, with some models showing increases in precipitation and some showing decreases.” [ENDQUOTE]

Some models showed increases in precipitation and others showed decreases. So the great Los Alamos lab doesn’t really know whether it will get wetter or drier in the Colorado basin over the next 50 years. Just like the rest of us.

Historical records show that the climate of the southwestern United States is generally wetter and cooler during El Nino years (when global average temperatures tend to rise) and the SW USA becomes drier and warmer during La Nina years (such as 2020) when global average temperatures tend to decrease. This means that the climate of the Colorado River basin tends to follow the opposite trend as “global average” temperatures, at least as far as the ENSO is concerned, so that predictions of climate change in the Colorado River basin based on global averages are sketchy at best.

In the Wasatch Mountains east of the Great Salt Lake (and the valley to the south), there is a hiking trail called the Bonneville Shoreline Trail, which follows the flanks of the mountains and roughly follows the contour line for 5,000 feet above sea level. This trail is nowhere near any “shoreline”, but geologists believe that there was once a much larger Lake Bonneville which connected the Great Salt Lake and Utah Lake (to the south) and flooded the Bonneville Salt Flats to the west, up to about a 5,000 ft elevation. The Great Salt Lake is currently at about 4,206 ft above sea level, and its maximum water depth is 33 feet.

If, thousands of years ago, there was such a large, 800-ft deep lake in northern Utah, the climate must have been much wetter then than now. Salt Lake City and the surrounding valley only gets about 15 inches (380 mm) per year of precipitation (with higher amounts in the mountains to the east). What caused the climate to dry out so that the large, deep Lake Bonneville dried out to relatively shallow remnants in the Great Salt Lake and Utah Lake, with some 600 square miles of dry valley in between? It probably wasn’t CO2 emissions from coal-fired power plants or diesel-powered trucks!

Clyde Spencer
April 9, 2021 8:50 am

… with some models showing increases in precipitation and some showing decreases.

This is nothing new. Global Circulation Models are known to produce contradictory precipitation forecasts at the regional scale. Yet, alarmists continue to use them instead of trying to figure out why they get inconsistent results, and then correct them. It is implicit ‘cherry picking’ to base a claim on some models getting the results that support the alarmist position. Intellectual honesty would require them to acknowledge that there is no preponderance of evidence to support forecasts such as they are attempting.

Patrick B
April 9, 2021 10:33 am

“We found … are projected to increase”

In other words, you didn’t “find” anything; nothing was proved by facts. What you are doing is predicting. So please state clear what your predictions are in a manner that we can test your predictions in a useful time frame. The corruption of scientific terminology and discourse by climate “scientists” is ridiculous. From claiming model runs as “experiments” that yield “data” to this “we found..” when all they are doing is issuing a new prediction, climate “scientists” are destroying useful terminology.

Steve Oregon
April 9, 2021 10:48 am

This is such hypothetical GIGO.
The entirety of this work is worse than useless as it uses sloppy conjecture to make wild assertions that have no real evidence and are impossible to ever really test or measure.
So the claims will just sit there as if they are scientific findings when they are nothing but invented nonsense.

April 10, 2021 3:43 pm

My guess at the reason why “extreme events increase” in models is Chaos Theory – – the small perturbations in rain, heat, cold, dry, wet, etc just keep ratcheting up as expected in any true chaotic system. Madness to try to run a predictive model out that far.

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