Guess Lowest Lake Level Spring 2022

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Eagle Rock said:
Good news, three different ways, for your methodology:

(1) For the week ending 2/7, drawdown was 78,340 af, 5827 af less than your 84 KAF figure. 12 weeks of that makes a 70 KAF difference and makes your minimum storage target 5336 KAF instead of 5266 KAF.

(2) For the last 10 years, average minimum spring elevation has occurred on April 20. 2021 was the outlier, so you had the right idea using May instead of May 25, but the decade average is another 11 days earlier than that. That knocks your 12 week number down to 10.3 weeks, and your target minimum storage up another (78.34 KAF/wk x 1.7 fewer weeks) 133 KAF, to 5469 KAF.

(3) Your method ignores the sedimentation since 1965, which has reduced the reservoir volume. See, for example, http://lakepowell.water-data.com/index2.php?elevation=3530.61, which shows a 211,000 af difference between October 1965 and February 2022 for the exact same reservoir elevation. So instead of looking for 5469 KAF back in 1965, you could adjust your method to look for 5680 KAF, which turns out to correspond to 3518'. That's a whole 6' higher than your calculation. Don't you feel better now?

But if this is a contest, I'll adjust my own guess up a little bit higher to account for some slowdown in the drawdown as we approach the minimum, and I'll guess 3520'.
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I've run the last week's numbers, with the drawdown from 2/6 to 2/13 of 67,100 af, multiplied by 11 weeks, adjusted upward by 210,944 af to account for sedimentation when trying to find a matching elevation, leading me to 7/11/1965 and a lake elevation of 3,520.81, so 3,520' for lowest level this spring is probably closer than 3,512' elevation. Marina operations at Bullfrog are probably still viable at 3,520', maybe not at 3,510'.

Release volumes are supposed to be 673 kaf in January, 539 kaf in February, 575 kaf in March, 501 kaf in April, 599 kaf in May, 678 kaf in June, going all of the way up to 858 kaf in August (https://www.usbr.gov/uc/water/crsp/studies/images/PowellRelease.png). Things could get pretty scary in July and August.
 
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Based on the Bureau of Reclamation's 24-month study for February, which came out today, I will provisionally go with their estimate of a lake level of 3522 in April. That said, with the current low snowpack and poor forward-looking projections for future precipitation, I think the Bureau may be a bit optimistic here. This same study also indicates a lake level of 3511 by March of next year (2023), so any new infrastructure (ramps, etc.) designed to work down to 3520 will be high and dry within a year of being completed. This may influence how much investment NPS really wants to put into facilities at Bullfrog Bay, which does not look viable as a marina site going forward.
 
Colorado Expat said:
Based on the Bureau of Reclamation's 24-month study for February, which came out today, I will provisionally go with their estimate of a lake level of 3522 in April. That said, with the current low snowpack and poor forward-looking projections for future precipitation, I think the Bureau may be a bit optimistic here.
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I agree that they are being optimistic, and will stick with my earlier 3520' guess.
 
A storm with 6-12 inch potential is forecast for the West Slope a week out (Feb 22). If that starts a pattern change, we could see the March and April we've been praying for. However, the long-range 10-15 day forecast re-builds the high pressure ridge through the first week of March for more dry conditions.

p.s. as of this weekend, we'll go below 90% of long-term average for snow water equivalent. Never seen such a prolonged flatline in snowpack, basically treading water since Christmas! Our storm next week could kick us temporarily back over 90%, but if it stays dry for another 10 days, we'll be threatening to go below 80%. BOR is only forecasting a 20-25 foot lake elevation rise from spring runoff. They may be right.
 
Not enough water in this storm to move the snow water needle more than 1%. The storm next week has potential to move us 3% or even 4%, but it takes consistent storms like that twice/week to keep up with the long-term average this time of year.
 
Here is Grand Jct weather office at 11:00 today.

Satellite and surface observations show the cold front is currently moving through the Salt Lake City area moving at about 45 mph.
The front will pass through eastern Utah and Western Colorado
through the day today, exiting to the southeast by this evening.
Radar indicates areas of light precip from Moab to the northeast
to the Elkhead Mountains. Haven`t seen any report of precipitation
at the surface yet. This indicates likely virga in the Grand
Junction area and southward due to drier lower levels. Areas to
the north should start seeing some light snow beginning in the
next few hours and spreading south through the day.
Look for skies to clear out from west to east Thursday morning as
cold, dry air moves in behind this system. The heavier snow will
be in the mountains and higher elevations east of a Dolores CO -
Baggs WY line. Overall, expect generally 2 to 6 inches in those areas,
so opted not to issue any weather advisories as storm will be a quick hitter and is mostly moisture starved.
 
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