March 2020 Lake Level Projection Update

JFRCalifornia

Well-Known Member
The USBR updated its lake level projections yesterday, and while it looks like things are starting to come in focus, there remains some uncertainty because the rain/snow season is not yet over. But the short story is this: it won't be as good as last year, with a projected total unregulated inflow of about 8.64 MAF, or about 80% of the recorded 30-year (1981-2010) average of 10.83 MAF. (By comparison, last year's unregulated inflow was about 13 MAF.) USBR now projects we will end up in the neighborhood of 3615-3616, with a chance it could be slightly higher or lower. Assuming we are close to bottoming out right now at 3601, that's a pretty modest rise in the lake of about 14-15 feet. The historical average rise is about 24 feet, and of course last year was about 53. Last year, you might recall, we ended up at about 3622, so if we end up at 3616, it's not that going to look that much different this year.

With planned releases for the water year of 8.23 MAF, the unregulated inflow of 8.64 more or less covers that, but with evaporation and diversions, will end up slightly negative on balance. Bottom line is we're going to end up pretty much in a holding pattern compared to last year, unless we get some late season precipitation surge as we did last year. Total lake volume is projected to end up at about 13.3 MAF, or 55% capacity.

A quick read of past water data looks like this year is shaping up to look something like 2007, which saw a rise from 3598 to 3612. For the record, 2007 ranked as the 37th best inflow year, so not that great... FYI, that year also did not have a very strong peak inflow, topping out at a shade under a 20,000 cfs peak on June 21...hopefully, this year has a much better peak inflow, which it will if we get a cold spring and late snowpack.

On its face, it also looks something like 2003, which saw a 12-foot rise from 3605-3617. But that year was different in that the rise only happened because of a very late spring surge following the terribly dry winter of 2002-03. For us, 2019-20 was not a terrible winter year, so a late spring surge could make a very positive difference this time.

Here's a link to the full story from USBR:

 

mtnpull

Well-Known Member
Thanks for the info. Seems kind of conservative to me. The snowpack is above average, but the inflow is projected to be only 80% of average? Me thinks there is some CYA in those estimates!!!
That is what I was thinking. But what do I know.
 

Lee F

New Member
That is what I was thinking. But what do I know.
With the reservoirs "full" above Lake Powell for this time of year and the snowpack above normal, I wonder too how they came up with a lower than average runoff. Last year I think a bit of water went into refilling the upper basin reservoirs, but that should not be the case this year.
 

JFRCalifornia

Well-Known Member
I'm inclined to agree with you that the projections for lake level rise seem low because of existing snowpack. That said, here's a few facts to think about. As of March 31, the collective current storage of the 28 reservoirs above Powell is about 7.2 MAF, or about 78% of the 9.2 MAF capacity of those reservoirs. (Flaming Gorge is the largest of these at 3.2 MAF in storage, or 86% full.) So there's still a little room to accept some snowmelt runoff even now in those reservoirs, and not release it all to Powell. USBR is projecting Powell to reach a high water mark of about 3616, which would be a net increase in volume in Powell of about 1.5 MAF compared to today. In practical terms, that means an average inflow of about 20,000 cfs each day for the next 75 days (assuming 10,000 cfs daily outflow), for a net inflow of 10,000 cfs each day through June 15.

Well, it's now at about 3600, which is probably close to the low water mark, which should happen any day now. In order to beat the USBR projection and reach, say 3630, and rise by 30 feet, you'd have to add a net inflow of about 3.1 MAF, or 1.5 million cfs, or about 20,000 cfs net inflow each day for about the next 75 days--that's essentially doubling the USBR's projected daily net inflow over that period. Assuming there's about 10,000 cfs outflow each day, that's a gross inflow of about 30,000 cfs each day from now until June 15. That's a tall order, not impossible, but would require a sustained very high water flow into Powell.

How often has Powell had a net inflow of at least 3.1 MAF during the spring rise? Pretty often, as it happens. Historically, Powell has risen about 2.75 MAF each spring if you take all the data back to 1965. Since 2000, that average rise is less--about 2.4 MAF. So USBR is actually projecting a slightly above average spring rise compared to the average from 2000-19. Last year was very big--during the spring, the lake rose in volume by about 4.95 MAF. Other recent big years that exceeded, say, 3.1 MAF, would include 2005, 2008, 2009, 2011, 2014 and 2017. So it happens pretty often, maybe 1 year out of every 3.

I'm hopeful we can get there, but it would require a huge sustained peak runoff from the snow to reservoirs, and then a big release from those reservoirs (which still can store up to 2 MAF) into Powell... We'll have a much better picture of this in about a month, but let's hope for more snow in the meantime...
 

John P Funk

Well-Known Member
refilling the upper basin reservoirs, but that should not be the case this year
This time last year the upper basin reservoirs were at about 60% full, today they are at nearly 80%. We've still got a few weeks to build snowpack in the high country, but in the lower elevations(we're at 6700' in SW Colorado) we've lost our snow with not much runoff. Only time will tell.
 

flowerbug

Well-Known Member
and then in the Delta they have some water flowing again! a lot of rains down there. :) :) :)


i'm hoping the recent rains/forecasts of rains put some of that into the Upper Colorado too! i saw what i thought was a bit of precipitation this past day. hope it actually made it to the ground...
 

flowerbug

Well-Known Member
got a nice picture from my sis who lives uphill from Santa Fe. they picked up some nice snow the past few days. enough that it may have taken a day or two to melt off. :)

i also see a nice bump in the graph for the snow pack! bring it on! more more more! :) :) :)

it is interesting as it looks like Momma Nature is really trying to follow that six year average...
 

dallas massie

Well-Known Member
The Glenwood Springs Post had a article yesterday saying only 75% of run off for the Colorado River . Due to dry soil ( no rain in august , sept and october.
 
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