Strong Monsoon Moisture Flow to Return Mid Week of July 11th Onward

Jackalope

Well-Known Member
Be carful out on the water next week and the week after ...


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Dorado

Escalante-Class Member
Anything is good, of course, but What if any forecasts on how this will impact lake level?

:unsure:
The monsoon only minimally affects lake levels. But is sure helps with soil moisture going in to the next runoff season! Besides, it is a huge relief for fire danger and general all around well being for all. Since the early start to the monsoon, the fire situation in the SW has improved greatly...
 

Kevin G

Well-Known Member
Looks like lake levels have maxed out for the year and the decline (hopefully slow) has started. I'm glad to see that there was enough water captured to give boaters a relatively good season on the lake, with access restored at Bullfrog. It's not perfect and not what we are all used to having, but have to tip my hat to the people who made it happen this year. Difficult challenges to overcome with low lake levels, losing Dangling Rope Marina access, new ramp construction. Happily the party goes on...just a smaller venue.
 

Trix

Escalante-Class Member
Hey, JFR, can you ferret out some of the monsoons that bumped up the lake level a significant amount as it was declining, say a foot or more (if they exist)? I remember (maybe erroneously) a fall trip when we got hammered with rain that kept us anchored for a day and before we pulled out, the lake had risen by about a foot. Not monsoonal, but a surprising rain impact. As Dorado already mentioned, minimal impact on lake levels, but interesting and beneficial.
 

JFRCalifornia

Escalante-Class Member
Hey, JFR, can you ferret out some of the monsoons that bumped up the lake level a significant amount as it was declining, say a foot or more (if they exist)? I remember (maybe erroneously) a fall trip when we got hammered with rain that kept us anchored for a day and before we pulled out, the lake had risen by about a foot. Not monsoonal, but a surprising rain impact. As Dorado already mentioned, minimal impact on lake levels, but interesting and beneficial.
Okay, I'll bite.

Well, by their nature, monsoon storms tend to be isolated and limited in duration, so their big picture effect on Lake Powell is pretty minimal. But it's not nothing. Just to cite a couple of recent examples, you just have to look back to August and September 2021, when there were two significant events, the most notable effect of which was the flooding along the Dirty Devil. Those storms also carved out a lot of sediment in Cathedral in the Desert. But what did they do for the level of Lake Powell?

In August 2021, inflows were declining (as expected), starting the month at about 8,000 cfs and dwindling as low as 4,000 as the month went on. But then a series of monsoon storms hit in mid-August, and inflow peaked at nearly 25,000 cfs on August 19. Until that day, the lake had been dropping about a foot every 5-6 days. But on August 19, it came up 3 inches, with a negligible rise the next day. After that, the declining pattern returned.

Another monsoon event hit right around September 1. This time the effect was similar, with inflow peaking at about 17,000 cfs. From Sept 1-3, the lake came up about another 3-4 inches before resuming its regular programming.

There's examples like that littered all over the database, some much bigger than that, but only a handful sustain a rise for more than a few days. Still, those events exist, and do make a difference since every drop helps... If you go way back, there were some pretty huge summertime events on the San Juan. For example, in early September 1970, big time storms over the upper San Juan caused peak inflow to Powell to hit 45,000 cfs on September 7. From September 6-9, the lake rose 1.5 feet before returning to its usual summertime decline.

And there was an unusual major late season rainy pattern starting in October 1972, ramping up by the end of the month and lasting into November. Powell inflow peaked at about 43,000 cfs on October 21, after rising 1.14 feet (!) the day before. From October 15 through Halloween, the lake rose 6 feet, and didn't start declining again until mid-December.

So yes, things like that can happen. Just not very often...
 
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Trix

Escalante-Class Member
As always, you never disappoint. Thank you! Your discussion highlights that a series of storms can raise the lake a few inches, but those instances may effectively be a half foot or so because the lake was dropping several inches a day. I'll continue to watch the Drought Monitor to see if monsoon will help basin soil moisture.
 

Trix

Escalante-Class Member
May not hit Powell but it’s raining on the Colorado basin. As often mentioned, increases soil moisture for next year's runoff.
 
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Jackalope

Well-Known Member
More coming .. And that the week I will be there.

WARNING: Hurricane Estelle to Enhance Arizona Monsoon with Major Increase in Storms After July 23rd


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Jackalope

Well-Known Member
More coming for Arizona... Some should hit Powell...

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