Lake Going Up a Foot a Day Now!

CATD8RII said:
4th in the record book. Nice. But it's still raining and looks to be raining all day today!!! Do I here second place.???
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This current rain event will go on for a couple more days. The San Juan is flowing above 10K cfs at Bluff UT which is about 4 days of flow from Lake Powell. We should see about a foot rise for several more days. Since mid September, the Navaho reservoir has added just over 100K acre feet and Vallecito has added 50K. The fall rise will be at least twice as much as the spring melt. I wonder if that is a record.
 
RobertGosselin said:
This current rain event will go on for a couple more days. The San Juan is flowing above 10K cfs at Bluff UT which is about 4 days of flow from Lake Powell. We should see about a foot rise for several more days. Since mid September, the Navaho reservoir has added just over 100K acre feet and Vallecito has added 50K. The fall rise will be at least twice as much as the spring melt. I wonder if that is a record.
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Here's a little perspective. The 13,300 cfs reported for the San Juan at Bluff on October 22 is in the top 1% of all-time flows recorded on that river in the last century on any date. The only times flow has ever exceeded this in any October was in 1937, 1941, 1947, 1969 and 1972, and most of those were just single day events, twelve days in all...

Impressive.
 
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RichieW13 said:
Yesterday was "only" 0.34' from the record. But look at how much different the actual content changed.

Yesterday increased about 56,000 acre-feet. But that October 6, 2006 record increased 128,000 acre-feet.
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Thinking about this some more. 128,000 acre-feet in one day is crazy. That is a 1% increase in lake content in one day.

But that means 56,000 feet yesterday was ALSO a 1% increase, albeit from a much lower starting point.
 
RichieW13 said:
Thinking about this some more. 128,000 acre-feet in one day is crazy. That is a 1% increase in lake content in one day.

But that means 56,000 feet yesterday was ALSO a 1% increase, albeit from a much lower starting point.
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There's a mystery to solve about that October 6, 2006 reading. The water database shows the inflow to Lake Powell that day to be 80,538 cfs. And yet, here's what the USGS shows for the flow that day just upstream along the three main sources of inflow:

Colorado - 8820 cfs
Green - 6250 cfs
San Juan - 4990 cfs

Clearly good flows that day, but they don't add up to anywhere near 80,000 cfs. So you might ask, were the flows higher in the previous days, and then finally worked their way down to Lake Powell on October 6? That is, was there a lag time?

Doesn't look that way. Here were the flows on those rivers three days earlier, on 10-3-06:

Colorado - 4340 cfs
Green - 1910 cfs
San Juan - 856 cfs

Even lower. So that doesn't explain it either. Maybe the dates are off somehow? So I looked at flows three days later, on 10-9-06:

Colorado - 7990 cfs
Green - 5400 cfs
San Juan - 7450 cfs

Definitely higher flows, but I still don't see how they add up to anywhere near 80,000 cfs... Looks like the peak flows on the rivers were indeed between Oct 6-8, but nowhere near what is shown on the database. Of course, there could have always been some data input error long ago, or the gages were read wrong. But for now, it remains a mystery...
 
A clue?
During the first week of October 2006, Durango and its surrounding regions in southwest Colorado experienced a historically significant, heavy precipitation event.
A slow-moving storm system tracked across the Southwest, drawing intense tropical moisture northward. While remote areas immediately around Durango averaged 1.18 inches of rainfall over the course of the storm, the heaviest downpours targeted the nearby high-altitude drainage basins. [1]
 
tt600 said:

Escalante Flood 2006 • Part III

www.canyontales.com www.canyontales.com
Escalante contributed
www.deseret.com

Flood damage devastating

Floods destroyed the only diversion dam and irrigation system serving rural farmers in Hanksville earlier this month, and now residents wonder if their town will ever be the same again.
www.deseret.com www.deseret.com
Dirty Devil contributed
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You're onto something there. Here were the flows on the Dirty Devil and Escalante:

Dirty Devil -

10-6-06 - 11,700 cfs
10-7-06 - 26,900 cfs (!!)

There's your major contributor...

But the Escalante peaked at only 291 cfs on 10-6-06, which is flood stage for sure, but not much help there by comparison. (FYI... the Escalante hit 1600+ cfs for a while today...)
 
JFRCalifornia said:
You're onto something there. Here were the flows on the Dirty Devil and Escalante:

Dirty Devil -

10-6-06 - 11,700 cfs
10-7-06 - 26,900 cfs (!!)

There's your major contributor...

But the Escalante peaked at only 291 cfs on 10-6-06, which is flood stage for sure, but not much help there by comparison. (FYI... the Escalante hit 1600+ cfs for a while today...)
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The Escalante is measured well upstream from where all the flooding occurred. Where it actually entered the lake it was above 10k . See the pictures in the article.
 
tt600 said:
The Escalante is measured well upstream from where all the flooding occurred. Where it actually entered the lake it was above 10k . See the pictures in the article.
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Those photos are really impressive... what an ordeal in October 2006! Thanks for sharing!

As for the data, here's where it gets interesting. First, here's a screenshot I took of today's version of the database website of the data from October 2006, showing the inflows in early to mid-October 2006, including 80,000+ cfs on October 6.

Screenshot 2026-10-22 at 7.51.20 PM.png

Now here's a screenshot of the same database, only as it was reported at the time, on October 12, 2006 (this was included in the article you had a link to):

October 2006.jpg

You'll notice that the outflows are pretty much the same in the two versions, and so is the amount of lake rise. But what's different are the inflows and the lake volume. I think I know why on the volumes (later corrections for sedimentation), but not sure why on the inflows. But you can see that the inflow reported on October 6 in the original version was only 8291 cfs, not 80,538. Same type of discrepacy on October 7 and 8... it's not until October 12 do they begin to re-align. I realize that the database has been updated and past errors corrected, but this discrepancy seems huge. It's especially curious because the lake level rise matches in the two versions of this dataset.

Possible explanations? Not sure. Some sort of math glitch in the spreadsheet translating lake volumes to flow? I have no idea. But I will say that the 2006 data pull from the time more closely aligns with the USGS flow data taken at the time (and still on the USGS website) than the flows shown in the 2026 version...

hmm...
 
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