# Colorado, 2020 Low Stream Flows



## theusualsuspect (Apr 11, 2014)

Yeah you are a little misguided. Snow pack was terrible across most of the state. Most of the moisture is March/April and we sort of blanked on those months. Check out this site and you can pull the reports for each month. 

http://www.nrcs.usda.gov/wps/portal/nrcs/main/co/snow/waterproducts/basin/

41% of normal as of June & 6% of last year. Those reports are great and break it down by watershed or you can just look at the overall. Have fun in that rabbit hole!


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## wamsley (Feb 28, 2011)

I hear ya' Fishn and I have wondered the same thing. I don't think you are misguided, the south half of Colorado did receive below average snowpack, but the north half did not and in the April river forecast from the USDA, the Upper Colorado, Yampa, White, South Platte were all expected to have at least average runoff (which I agree did not seem to happen). This is even more strange when I look at the Colorado Snotel Peak, which puts the Colorado River basin peak date at April 23- well past the normal and was slightly above average at that time.

With all that said, the rivers I look most closely at are the Colorado and Roaring Fork and my only explanations are that the heat wave that hit late April and early May causes such a dramatic loss of snow early, that we experienced less run off late. Perhaps COVID affected the field scientists from collecting as much data for snotel as well, so perhaps the snowpack was actually over reported? Lastly, for the Colorado, it seems like Dillon and Green Mt Reservoir were able to hold the incoming snowmelt- not sure if this was possible from sending water through the divide, excellent planning by the Bureau of Reclemation and Denver Water or that the reservoirs became 'too empty' from the assumption runoff would be greater than it was. Either way, this limited a large tributary from increasing the Colorado River's flow.

Anyhow, that's all I got and I feel as confused as you. Strange times...


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## cayo 2 (Apr 20, 2007)

Above average temperatures is the explanation that makes the most sense.They were reporting above average snowpack in the northern basins [the Ark was over 90% ]well into the stay home recommendation period.Lack of late snow is probably another factor.


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## Heywood (Apr 12, 2019)

Wind blew alot of snow away (via sublimation) before it could melt and runoff.


Also a major soil moisture deficit from the hot dry summer last year so stuff that did melt went to the soil/trees before running down a river


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## MaverickUSC (Jun 24, 2014)

Northern drainages' snowpack peaked above normal, April 21st most places, much later than normal. We also had an extremely warm May relatively, total opposite of last year, yielding an earlier runoff peak than normal. 

The main thing I am seeing with the CO is strange behavior from the upstream reservoirs. Dillion, Green Mountain, Wolford, Williams Fork, Windy Gap, Granby, and Grand Lake are all very full and releasing less water than normal. Denver is calling for more water than normal, so a bunch of it is going over The Divide. 

The southern side of the state has always had a grim outlook this season.


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## FishnPhil (Aug 27, 2007)

I agree what a difference a year makes, eh?! Although, last year was also one of the most unique I can remember. 

I had noticed this trend a few weeks ago when looking at the stremflows also, everything was running way low compared to normal. I figured it was due to a cool down for those days I looked, but then looking again this week, and looking back, I was a bit surprised. 

Yes, the Southern part of the state is the desert. It might not be officially mapped that way (nature doesn't care about our maps anyways) but there are sand dunes there, so in my opinion it's a desert!!  

I had noticed how low the South side was, it pulled the state average down to ~100% (in March when I looked) and the Northern ranges were all over 100% to account for that. I tend to look at the snowpack by area for exactly that reason. Which again is why I was surprised seeing all the rivers in the central/North part of the state running far below average. 

Thank you all for the information! With most things there are likely several variables. It just caught me really off guard to see tailwaters and freestones at, what I would consider, prime post runoff flows when normally I expect these flows to hit the week after the 4th. 

For me, last year wasn't so great because of the high flows making fishing more difficult but I bet you kayakers loved it!! (and it did the fish good too) This year, seems to be the opposite. The ebbs and flows, I guess


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## Fuzzie (Jan 23, 2009)

I have one very simple answer. Trans Continental Diversion. The Front Range de-waters the western slope. That is it...


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## cain (Dec 28, 2011)

I'd have to agree with the wind theory. Up here on Rabbit Ears Pass the wind has been crazy strong for the last 2 months almost every day and the snow just disappeared by about a foot every day when there still was snow on the ground. Also, We are losing a lot of water to the front range so people can have nice green lawns. You would think with the current conditions they would put watering restrictions in place down below.


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## Andy H. (Oct 13, 2003)

FishnPhil, You're not missing anything but a good runoff season. 

A big part of the low flows this year was the lack of any appreciable soil moisture going into the winter, then storms were tracking south of Colorado and gave us the dry spring we had. Whatever snow was left when the runoff started had to saturate the soil beneath it before running off. As early as the beginning of May, the Lake Powell inflow was forecast at 4.5 million acre-feet, which is really low compared to the Upper Basin Compact expectation of 7.5 MAF. While trans-continental divide diversions play a role, as always, their influence on the Western Slope runoff is small compared to the impacts of the poor snowpack, soil moisture, and windy conditions. 

Here's a blog post on this year's runoff from the Western water management world. The comments are generally from technical folks in the Western water supply hydrology sphere who know what they're talking about. The discussion in the comments makes for an educational read in itself.

“sneaky drought” in the Colorado River Basin

-AH


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