How low will it go?

Dillonwhitt

Member
So we know the lake came up 50' (I know a little more then 50)last year. But now my question is how low do we think it will get? As of today the lake is sitting at 3607.89, I'm guessing we will see 13' of drop befor it makes it's come back.... please don't hold me to that it's a very uneducated guess...
 

Dougie

New Member
Historical average spring runoff raises the lake about 25 feet. Upper Colorado and San Juan and Escalante water levels are presently averaging about 115% of normal, but more than half the winter precipitation is still to come. We could continue to run slightly above normal, who knows?

If we get 115% of runoff, we'll rise about 28 feet. If we assume a 3598 start point, adding 28 feet would take us to 3626 this year. Last summer the top water level was 3622, so we'd be 4 feet higher than last year at the peak, which is usually reached in the first week of July.

Let's hope for a snowy winter and early spring! Another 50 foot rise is still possible if that happens, but it's a long shot. This would almost put us back up to 2011 levels.
 

JFRCalifornia

Well-Known Member
Historical average spring runoff raises the lake about 25 feet. Upper Colorado and San Juan and Escalante water levels are presently averaging about 115% of normal, but more than half the winter precipitation is still to come. We could continue to run slightly above normal, who knows?

If we get 115% of runoff, we'll rise about 28 feet. If we assume a 3598 start point, adding 28 feet would take us to 3626 this year. Last summer the top water level was 3622, so we'd be 4 feet higher than last year at the peak, which is usually reached in the first week of July.

Let's hope for a snowy winter and early spring! Another 50 foot rise is still possible if that happens, but it's a long shot. This would almost put us back up to 2011 levels.
That's a pretty good analysis, and you might be right on the mark with your 3626 prediction, though much depends on the snowpack ahead... Historically, the lake averages a 23-foot drop from the peak in one year to the low the following spring, based on all data 1965-2019. If you just isolate the time from 2000-2019, that number is 27 feet. That suggests we'll end up somewhere in the neighborhood of 3595-3599 as a low point in early spring 2020. Actually, it's been remarkably consistent in that 20-27 foot range since 2008, the only outliers being in the years following a bad drought winter, notably over the winters of 2012-13 and 2018-19, where the drops were 41-43 feet. In the years since the lake was first full in 1980, the smallest drop was 6 feet (1982-83), then 13 feet (2006-07), and only a couple of others less than 20 feet. And the largest drop? That's the 43 feet in the winter of 2018-19...which explains in part why we had such a huge rebound in the spring of 2019, because when the lake is very low, it takes less volume to get those first few feet of rise...

And as far as the average rise in spring? From 1965-2019, it's 24 feet. Since 2000, it's 23 feet. And last year of course was the anomalous 53.17 feet... Unlike the drops, there's huge variation in the rises. For the years where it's started anywhere from 3590-3600 as a minimum (which is 7 years), the average rise is on the order of 27 feet, although with a huge variation (from 5 feet in 2013, when it rose from 3596 to 3601; ranging up to 58 feet in 1973, when it rose from 3591 to 3649)...

Of course, all this is pretty much meaningless at this point, but if we just follow the averages, we'll drop to about 3595-3599, then rebound to about 3618-3626... pretty much like Dougie said!

...and the average date of when the lake bottoms out is April 1. In 2019, it was April 10. The earliest minimum since it filled in 1980? Feb 15, 1982... Feb 25, 1983... Feb 28, 1993... And the latest? May 26, 2002... May 25, 1990...

But by far most minimums occurred anywhere between March 15 and April 15...
 
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Dougie

New Member
At this point in 1983 the hydrology of the Upper Colorado basis did not foreshadow anything close to the runoff we ended up getting that spring. It was the exceptional snowfalls of April into May of that year that pulled the surprise. Usually the Upper Colorado storage on April 1 is about the high point for the year, and by looking at the storage levels on that day, you can pretty well predict the spring runoff. But not in 1983, when more than a quarter of the entire winter's precipitation occurred AFTER April 1st. So anything could still happen this winter. Inflows reached 120,000 cubic feet per second in 1983. I don't think we've exceeded 78,000 cfs in any year for the past 20, and most years we barely each 60,000 for one or two days of peak flow. Those 1983 inflows would kick the lake up more than 2 feet per day at present levels. They were enough to raise the lake one foot a day even at 3695 elevation where the surface has spread out across the flatlands in Padre, Warm Springs, and Wahweap Bays. That year on July 15 the lake was held at its all-time peak of 3708 only because they installed 8 foot flashboards on top of the spillway gates which are at 3700. I went to Rainbow Bridge that year and there was 20 feet of water in the canyon right underneath. Cathedral in the Desert was so full you could skim right over the top of both the waterfalls and go back nearly a half mile, while Davis Gulch was full within just a couple hundred yards of Bement Arch, and La Gorce was totally bisected by water so you could swim through from one side to the other. At the back of the Escalante, you could drive your boat right under Stevens Arch at Coyote Gulch. And for some years after that, the cutoff from Bullfrog to Halls Creek at 3670 was the best shortcut on the lake if you liked to stay close to the marina and have access to beach camping galore. In 1983 the water in Smith Fork was almost up to the beginning of the narrows, and you could boat up Iceberg and stop right under the sheer back walls at the end of each of its 3 main fingers. Those were the days! We can only hope for water like that again--it would take 2 big winters to do the trick. I say let's start right now! Pray for snow, enough that we can share downstream with Lake Mead, and give the river runners a great spring season with 35,000 CFS or better to give some cheap thrills for our tourists.
 

JFRCalifornia

Well-Known Member
I think you're speaking my language...Great stuff! And great descriptions of 1983--you're right, that was an exceptional spring! And the thing about that 120K cfs is that it happened on July 1, exceptionally late as you know...In 1984, it also hit 120K, but that was at the end of May, a more predictable timing...

In the past 20 years, it did hit 95K cfs in 2011(June 16), and of course it reached 78K this past spring on June 18... but other than that, the only other years over 80K besides 1983-84 were in 1979, 1986, 1993, 1995, and 1997... but none exceeded 96K in 1995... which is another reason 1983-84 were so exceptional...

...1983 and 1984 were both off the charts in terms of flow, but very different in terms of timing. Both years saw sustained peak inflows of 100K+ cfs, and both hit a peak of over 120K cfs. In 1983, that 100K+ flow lasted 9 days, and in 1984 it lasted 2 weeks!! Wow… In both years, you had sustained inflow of 85K+ cfs lasting roughly a month—5 weeks in the case of 1983! The big difference was that in 1984, the peak happened in the last week of May and first week of June. In 1983, it snuck up on everybody—and the peak flow was delayed until the last week of June and the first week of July.

You're right, if we had another 1983-84 double punch, we'd make some real progress on filling the lake.

Imagine if those two years happened starting this coming spring, with a lake level starting at 3598 in early April... How high would the lake rise? Well, first consider the inflow alone—in both 1983 and ’84 from April 1 to August 31, about 15 MAF entered the lake! In just May through July alone, it was about 12.3 MAF. That’s an incredible amount, roughly the annual flow of the Colorado River system in one spring runoff. In both 1983 and ‘84, the Bureau released over 10 MAF during that time to manage the nearly-full lake.

But what if they had been able to release just the minimum to meet the normal annual release requirement of 8.23-9 MAF? In that scenario, the average daily release is 11-12,000 cfs. To model that, I applied the 9.0 MAF scenario by assuming a daily release of 12,432 cfs during that entire period of April 1-August 31. That results in a total release of about 3.7 MAF during that period. So if you do the math, and subtract that release from the same period 1983-84 inflows of about 15 MAF, you end up with a net inflow of a little over 11 MAF for each year. (The Bureau assumes annual evaporation loss is about 0.4 MAF, which I didn’t account for.)

Here’s what would happen if you added a net 11 MAF in two straight years to Lake Powell assuming a starting point of 3598, which is where we're likely to be by the end of March 2020 (lake volume of 11.6 MAF). That would bring the lake up to 22.6 MAF in volume by the end of summer in the first year, minus evaporation of 0.4 MAF, so about 22.2 MAF. That means you would end up with about a 88-foot rise, ending at 3686 (!!). At that point, the lake would be over 85% full, and higher than the level as where it started in the spring of 1983. So that means a second straight year like the first would be almost exactly like what ended up actually happening in 1983-84—the lake would be full, with massive releases.

That would be great... we can only hope...

Thanks for bringing your voice to this discussion!!
 
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Flow

Member
There's so much uncertainty surrounding the amount of water that was absorbed into the extremely dry soils last year, which I believe aided this year's wildfire season never getting too bad in Utah at least. Now that our ground is saturated with water, another year like the last would be incredible and I would be curious to see how much additional water we would see from an equal amount of SWE as last year. I'm just hoping for another year of above-average snowpack and everything above 100% is just the icing on the cake.
 

JFRCalifornia

Well-Known Member
Also in 2019, we didn't hit above 80,000 cfs at any point but we sustained 49,000+ cfs for twenty-three days straight in June which is pretty remarkable.
Yep, that sustained flow so late in the season was not only remarkable but unusual--there were 58 straight days of 30K cfs last year, from May 19 to July 15... and with the exceptions of 2008 and 2011, that period was the longest since 1998. And with the exception of 2011, the latest date of a 30K cfs flow since 1986.

In terms of lake level rise, the 16 straight days exceeding a 1-foot rise in 2019 was matched only once, in 1993. But it was by far the latest such sustained rise, happening from June 9-24...
 

wayne gustaveson

Moderator
Staff member
Thanks for the great insight and outlining what may happen in 2020. I am impressed by your knowledge of all who have participated in this thread. I know who to reach out to if I need help in predicting what will happen in the future. What we do know is that runoff in 2019 was unusual and less runoff is more likely in 2020. Personally, I hope we get another high water year so we can let these fat fish swimming now get even bigger and better in the future. That would be AMAZING!
 

birdsnest

Well-Known Member
I think you're speaking my language...Great stuff! And great descriptions of 1983--you're right, that was an exceptional spring! And the thing about that 120K cfs is that it happened on July 1, exceptionally late as you know...In 1984, it also hit 120K, but that was at the end of May, a more predictable timing...

In the past 20 years, it did hit 95K cfs in 2011(June 16), and of course it reached 78K this past spring on June 18... but other than that, the only other years over 80K were in 1979, 1986, 1993, 1995, and 1997... but none exceeded 96K in 1995... which is another reason 1983-84 were so exceptional...

...1983 and 1984 were both off the charts in terms of flow, but very different in terms of timing. Both years saw sustained peak inflows of 100K+ cfs, and both hit a peak of over 120K cfs. In 1983, that 100K+ flow lasted 9 days, and in 1984 it lasted 2 weeks!! Wow… In both years, you had sustained inflow of 85K+ cfs lasting roughly a month—5 weeks in the case of 1983! The big difference was that in 1984, the peak happened in the last week of May and first week of June. In 1983, it snuck up on everybody—and the peak flow was delayed until the last week of June and the first week of July.

You're right, if we had another 1983-84 double punch, we'd make some real progress on filling the lake.

Imagine if those two years happened starting this coming spring, with a lake level starting at 3598 in early April... How high would the lake rise? Well, first consider the inflow alone—in both 1983 and ’84 from April 1 to August 31, about 15 MAF entered the lake! In just May through July alone, it was about 12.3 MAF. That’s an incredible amount, roughly the annual flow of the Colorado River system in one spring runoff. In both 1983 and ‘84, the Bureau released over 10 MAF during that time to manage the nearly-full lake.

But what if they had been able to release just the minimum to meet the normal annual release requirement of 8.23-9 MAF? In that scenario, the average daily release is 11-12,000 cfs. To model that, I applied the 9.0 MAF scenario by assuming a daily release of 12,432 cfs during that entire period of April 1-August 31. That results in a total release of about 3.7 MAF during that period. So if you do the math, and subtract that release from the same period 1983-84 inflows of about 15 MAF, you end up with a net inflow of a little over 11 MAF for each year. (The Bureau assumes annual evaporation loss is about 0.4 MAF, which I didn’t account for.)

Here’s what would happen if you added a net 11 MAF in two straight years to Lake Powell assuming a starting point of 3598, which is where we're likely to be by the end of March 2020 (lake volume of 11.6 MAF). That would bring the lake up to 22.6 MAF in volume by the end of summer in the first year, minus evaporation of 0.4 MAF, so about 22.2 MAF. That means you would end up with about a 88-foot rise, ending at 3686 (!!). At that point, the lake would be over 85% full, and higher than the level as where it started in the spring of 1983. So that means a second straight year like the first would be almost exactly like what ended up actually happening in 1983-84—the lake would be full, with massive releases.

That would be great... we can only hope...

Thanks for bringing your voice to this discussion!!
I must say that between JFR and and Dougie, we have a couple of Water Wizards. JFR finally has an equal to bounce his calculations and forecasts off of. I can just sit back and listen... Good for us to have these guys on board.
 

flowerbug

Active Member
just so you know, i love water nerds. :) this is my kinda thread.

what i am curious about is that we've had a great water season last year, but a somewhat dry summer that the ground moisture levels aren't all that great, yet i think it still makes some impact on the following year as we've seen the above average river flows. so with that in mind i think even an average year of snow for the snow pack may still result in somewhat above average level results.

this is my guess. :)
 

flowerbug

Active Member
there's an excellent bunch of water nerd sites and as only one tip into that pool i'll point to:


and if you read there you'll note i'm disagreeing with the forecast in a recent post there (saying 82 percent). hmm. we'll see...

p.s. if i could send the 4-5 inches of rain we had the end of December i surely would. that was a large storm here and we sure didn't need the extra moisture.
 

JFRCalifornia

Well-Known Member
I love all this water geekery!! I can say here in Southwest Colorado, winter is off to a fabulous start. :)

Looking forward to another 50+foot rise.

Tiff
I think geekery is a legitimate word, but of course used only by geeks. :) But to flowerbug's post, that "82% of normal" inflow forecast is coming directly from USBR... which they admit is a wild guess right now because everything depends on the months ahead and what falls out of the sky during that time. But that "82%" would mean 8.93 MAF coming into the lake, which feels low given the good start to the season and the heavy spring runoff....Under USBR's "max" scenario, they guess up to 12.82 MAF inflow, which is comparable to what happened last year... of course recall that early season predictions last year forecasted nothing but misery, and a peak lake level around 3580...wrong... That tune got changed as spring rolled around.

Right now, their current (Jan 6) crystal ball forecasts the likely lake peak at about 3614, but the forecast range is huge, anywhere from 3605-3657. Talk about hedging your bets! They'd never make it in the annual WaynesWords contest...

Here's the links to the current elevation and inflow projections from USBR...


 

flowerbug

Active Member
i'm just hoping for more Pineapple Expresses separated by a few days at least so they can adjust everything to handle them. capture it, soak it in, whatever they can do. last season it was really good in terms of there wasn't a huge amount of flooding most of the season. they were able to top off almost every reservoir.

now that ORO is back in operation (and gradually filling up :) ) it looks to be a pretty good year because they are already at a fairly full level in a lot of the CA reservoirs. what this means for the 2nd year in a row they may be able to not draw down Lake Mead as much as they normally would have in the past.

this changes the game out there quite a bit. if you get AZ and CA cooperating instead of fighting over a limited resource... i'm not sure they're there yet, but the next round of river negotiations is going to be interesting to watch.
 

JFRCalifornia

Well-Known Member
i'm just hoping for more Pineapple Expresses separated by a few days at least so they can adjust everything to handle them. capture it, soak it in, whatever they can do. last season it was really good in terms of there wasn't a huge amount of flooding most of the season. they were able to top off almost every reservoir.

now that ORO is back in operation (and gradually filling up :) ) it looks to be a pretty good year because they are already at a fairly full level in a lot of the CA reservoirs. what this means for the 2nd year in a row they may be able to not draw down Lake Mead as much as they normally would have in the past.

this changes the game out there quite a bit. if you get AZ and CA cooperating instead of fighting over a limited resource... i'm not sure they're there yet, but the next round of river negotiations is going to be interesting to watch.
I like the optimistic thinking! In the case of CA, it’s interesting and of course I see it up close living here. Sierra snowpack is good so far, headed to Mammoth to ski in a couple weeks, great conditions... This bodes well for water deliveries under the state water project, and here on the central coast we use some of that water. But none of the Colorado River water that goes to CA is used anywhere outside of Southern California. mostly some LA area cities and of course Imperial Valley ag users... all that to say, a good water year in most of CA doesn’t have too much bearing on how much water may or may not come from the Colorado River...

AZ and CA have been cooperating of late, which is good, and both stay well within their max allotments based on recent cooperative agreements among the basin states. But if either state cut back even more, that would tend to benefit Mead more than Powell...what really affects Powell is how much USBR schedules for release through Glen Canyon Dam, and that’s not so much a response to likely downstream water use, but based on set release protocols to ensure lower basin delivery whether or not they intend to use it anytime soon. If those states cut back use, Mead goes up. And it’s very much in AZ’s interest be keep Mead up, because if it drops too much, and something’s got to give, they are junior to CA in terms of water rights...

great topic, much more there...
 
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