Spring Runoff Reality Check - May 7

JFRCalifornia

Keeper of San Juan Secrets
I've been seeing a lot of concern on this forum about the runoff being less than hoped, and how that means doomsday is right around the corner. Let me untangle the most recent data we have and put it into perspective, and give you my take on what it all more realistically adds up to.

First off, let's look at how April played out compared to what USBR predicted based on NOAA's information:

USBR projected April inflow - 645,000 af
Actual April inflow - 659,000 af

USBR projected April 30 lake level - 3559.4
Actual April 30 lake level - 3559.8

All right, so Lake Powell actually outperformed what USBR thought would happen in April. Okay, so what about May?

USBR projected May inflow - 1.63 maf
USBR projected May 31 lake level - 3572.1

It's way too early in May to know whether or not the reservoir performs as predicted. May is almost always the "make-or-break" month, but you almost never know what it will end up like until you're more than halfway through the month. That's what the record shows. To me, the key indicators for this year are still reasonably good:

1. In 2024, the outflow so far has been exactly as USBR has planned, which in historic terms is very low--good for Lake Powell. For May, USBR is essentially going to match outflows we saw in April. That means about 600,000 af, or roughly 9700 cfs on average each day. That's pretty much exactly what we're seeing so far in May.

2. For inflow to reach the USBR-projected 1.63 maf, that means an average of 26,500 cfs each day. Totally achievable. This year looks a lot like 2015 or 2016, very average years. In 2015, May started out with less than 10,000 cfs, and increased to over 30,000 cfs by the end of the month--inflow for the month was about 1.4 maf. May 2016 was a little better, starting at 17,000 cfs and peaking at just over 50,000 cfs that month--total inflow was about 1.9 maf. Seems reasonable we'll end up somewhere in between, which would be right in line with what USBR projects. These recent shots of rain and snow could bump that just a bit, hard to say, but let's not count on that.

3. The Upper Basin SWE is now right on the median for this date, and in general the sub-basins are pretty much in the same boat, plus or minus. Again, this all is in line with what USBR has been projecting.

4. Then there's the CBRFC water supply projection, which is really the key data set that forms the heart of USBR's guesses. On May 1, the official "median" projection for April 1-August 1 was 5.1 maf. On May 7, that's up to 5.4 maf. Is that correct? Who knows, but I'm guessing that CBRFC knows better than any of us. Of course, their latest (April) 24-Month Study was based on 5.7 maf of water supply through July, so we're still 0.3 maf short of that. If that's really true, and if they keep their operations as planned, then instead of the peak of 3589 they predicted, we're looking at something closer to 3585.

Of course, all that could be wrong--still way too early to tell. As I say, let's revisit this question on May 20. We'll know much better then. But one thing's for certain--it's way too early to start writing this runoff year off yet.
 
Last edited:
It is hard to get too far into doom and gloom at this point. The typical fill curve for the lake over the past five years has had variability in timing of how the upward swing occurs and when it happens. The curve for 2024 appears to be a transposition of 2019, which would be a great year to emulate (I'm pretty sure it won't be matched). I think the concern comes from the snowpack, which is at 90% of comparable for the date. However, the storms we have had over the past few days have really overdelivered in the upper basin. We will have to see how that translates to the river, but we are close enough to median values and the upstream reservoirs are in such good shape, I don't think anyone should be super concerned. Plus we are still in better shape than 2021 or 2022. The likelihood of any disruption similar to what we saw in either of those years is zero.

Screenshot 2024-05-07 at 4.39.14 PM.png
 
I wonder how many days (if any) we will have 1 foot increases like last year.
I'd say it's highly unlikely we'll have any. Actually, 1-foot+ rises have rarely happened in the lake's history... only in a few years, mostly when the lake was very low. I might not have them all right, but off the top of my head I'm thinking 1964, 1968, 1973, maybe a couple in 1979, a day or two in 1984, 1993, 2005, 2011, 2019 and then last year in 2023. What most of those years have in common is that they started very low and were big runoff years with minimal outflows. So that's why certain big years like 1983 never saw a daily 1-foot rise even with a huge runoff...
 
I am a new member on this forum and I must say that there a lot of very intelligent people that contribute to information provided. I am wondering looking at the graph for the last 6 years it looks like spring 2022 saw almost a 19 foot rise in Lake Powell water level despite average snowfall for water year 2022. How did lake Powell see that 19 foot rise? Anyone.
 
Last edited by a moderator:
I am a new member on this forum and I must say that there a lot of very intelligent people that contribute to information provided. I am wondering looking at the graph for the last 6 years it looks like spring 2022 saw almost a 19 foot rise in Lake Powell water level despite average snowfall for water year 2022. How did lake Powell see that 19 foot rise? Anyone.
Welcome to the forum!

You're right that the lake rose from 3522 to about 3539 in spring 2022, but it's more instructive to look at the change in lake volume during that time, which was only about 0.6 maf (from about 5.8 to 6.4 maf live storage). When the lake is low, it doesn't take as much water to make it go up. Conversely, when it loses volume when the lake is already low, it drops fast. So it's very sensitive to inflow and outflow at low lake levels.

Keep in mind that half of the total storage volume of Lake Powell is in the uppermost 100 feet. That is, when the lake is at 3600, it's roughly half full. Again, another indicator of how sensitive the lake is to big seasonal variations when it's below 3600.

It's also worth noting that in 2022, USBR minimized the release through the dam to 7.0 maf for the water year, the lowest it had done since 1964 when they were trying hard to fill the lake to at least minimum power pool (3490). That kept the lake "afloat" during an otherwise poor runoff year...

As for the intelligence of the people on this site, I'd agree it's pretty darn good. The USBR and NPS would do well to read the posts here...
 
Last edited by a moderator:
Back to 1 foot in a day. Interesting to contemplate, remembering the pre internet days when we stuck a stick at shoreline at dinner to see the overnight rise, vaguely recall half foot increases and tight anchor lines. About 40k af inflow and 20k af outflow yesterday, about 3 inch rise. So, at this lake level would need about 160k af inflow to get a daily foot rise.
What are the all time top daily inflows on your spreadsheet? TIA!
 
Back to 1 foot in a day. Interesting to contemplate, remembering the pre internet days when we stuck a stick at shoreline at dinner to see the overnight rise, vaguely recall half foot increases and tight anchor lines. About 40k af inflow and 20k af outflow yesterday, about 3 inch rise. So, at this lake level would need about 160k af inflow to get a daily foot rise.
What are the all time top daily inflows on your spreadsheet? TIA!
You know I can't resist a challenge like that... :)

Top inflows? Or top daily rises? I'll go with the rises for now...

Biggest one day rises:

Every day from 5-21 to 6-1-64 was at least 2.1 feet (!!), and over 3 feet from 5-21 to 5-30-64, with the biggest rise being:

5-24-64 - 3.40 feet (inflow 44,378 cfs; outflow 1,020 cfs)

Remember that USBR kept outflows at about 1000 cfs that spring to fill the lake. Even with those huge rises, inflow was never really more than 50,000 cfs...

Apart from 1964, here's your top ten:

5-22-23 - 1.63 feet (inflow 73,426 cfs; outflow 17,705 cfs)
5-27-05 - 1.55 feet
6-9-68 - 1.54 feet
6-8-68 - 1.51 feet
5-26-05 - 1.50 feet
5-28-05 - 1.50 feet
5-29-05 - 1.50 feet
5-21-23 - 1.49 feet
5-23-23 - 1.49 feet
5-20-23 - 1.48 feet
5-30-23 - 1.48 feet

You'll notice they're almost all in late May. As for other big years with their peaks:

6-15-19 - 1.28 feet
5-24-73 - 1.24 feet
5-30-93 - 1.21 feet
6-11-11 - 1.13 feet

The database also shows 1.76 feet on 6-1-84, but I think that's wrong, since all the days around it with the same inflow/outflow are closer to 0.80 feet... looks like they corrected that error the next day by making the inflow negative...
 
John just posted, so I am late on this, but thought I would post my work anyway.

There are 114 days since 1970 where the daily rise was 1 foot or greater. The greatest daily rises all occurred in either 2005 or 2023.
1715197714235.png

As you probably recall, both were major recovery years, starting from very low storage levels.

Interestingly, there was one day with a 1.05 ft rise in 1984 (6/1/84), which also happens to be the greatest increase in storage ever, with a 268,000 acre-feet increase (!!!!). John says this is an error and that is likely so, though on 5/20 they also had a similar magnitude storage difference.

The top 10 all time days were all in 1964:

1715197981805.png

Fortunately, there weren't a lot of facilities that required care, since I can't imagine how chaotic a 3 ft rise would be now.

The top 10 increases in daily storage by day are a mix of 1984, 1993, and 1995. I wouldn't mind seeing a few days like that as the increases we saw last year were high, but ultimately the highest inflow last year ranked 121st all time.

1715198202998.png
 
John just posted, so I am late on this, but thought I would post my work anyway.

There are 114 days since 1970 where the daily rise was 1 foot or greater. The greatest daily rises all occurred in either 2005 or 2023.
View attachment 27705

As you probably recall, both were major recovery years, starting from very low storage levels.

Interestingly, there was one day with a 1.05 ft rise in 1984 (6/1/84), which also happens to be the greatest increase in storage ever, with a 268,000 acre-feet increase (!!!!). John says this is an error and that is likely so, though on 5/20 they also had a similar magnitude storage difference.

The top 10 all time days were all in 1964:

View attachment 27706

Fortunately, there weren't a lot of facilities that required care, since I can't imagine how chaotic a 3 ft rise would be now.

The top 10 increases in daily storage by day are a mix of 1984, 1993, and 1995. I wouldn't mind seeing a few days like that as the increases we saw last year were high, but ultimately the highest inflow last year ranked 121st all time.

View attachment 27707
That’s great work, nzaugg!! Your data is a lot more organized than mine. I believe in a cluttered desktop and lots of chaos covered with a thin veneer of actual thought.
 
I am a new member on this forum and I must say that there a lot of very intelligent people that contribute to information provided. I am wondering looking at the graph for the last 6 years it looks like spring 2022 saw almost a 19 foot rise in Lake Powell water level despite average snowfall for water year 2022. How did lake Powell see that 19 foot rise? Anyone.
You’re right. There are a lot of very smart people on this site….the rest of us are fishermen 😂😂😂😂
 
Your work sure does make a liar out of me. In 1984 I was there the last week of May and my measuring system, put a stick at the edge of the water then check it sometime the next day, told me the water was rising over a foot a day. I went so far as to say I saw a foot and a half per day. Boy my sticks sure did get longer. lol
Thanks guys.
 
I still have hopes for 3600 🤞but either way it's sure nice not to be talking about dead power pool and possible marina closings and crap like that! I guess it could be the long way around antelope all summer but that's ok too, it might help keep the crowds down up lake, that and no fuel up there. That all could change by next year so I'd see that as a last chance for some solitude. That part has been nice
 
Last edited:
SO looking at the weather report as of today 5/9 they gonna get 8-16" more of snow in most of Central Colorado which means most the upper elevations still have yet to melt as they been nicely frozen up still this late in season which is good. I do see the big melt starting by the 20th for sure though as old man winter can't usually hang on that long. I have friend in Telluride working on a resort and he said they have had snow flurries off and on for 3 weeks every few days so long term looks good!!!
 
While this is not much it's something at the 9000' level in central AZ mountains there is still snow on the ground in Sunrise...check the camera for yourself
, this water flows to the LCR which dumps into the grand canyon...again while this alone is not much it bodes well that we are into mid May and theres still white stuff on the ground in Az mountains
 
Your work sure does make a liar out of me. In 1984 I was there the last week of May and my measuring system, put a stick at the edge of the water then check it sometime the next day, told me the water was rising over a foot a day. I went so far as to say I saw a foot and a half per day. Boy my sticks sure did get longer. lol
Thanks guys.
Must have used the yard stick most fishermen use to measure their catch! The amazing thing about that yardstick is the measurement reads higher every year. :D
 
While this is not much it's something at the 9000' level in central AZ mountains there is still snow on the ground in Sunrise...check the camera for yourself
, this water flows to the LCR which dumps into the grand canyon...again while this alone is not much it bodes well that we are into mid May and theres still white stuff on the ground in Az mountains
Sunrise runs into the Salt River then to Roosevelt Lake. In a way this snow still helps Powell, the more water for the SRP the less Phoenix and Tucson needs from the Colorado system.
 
Back
Top