In the green today

[Piece-O-Crappie]

Well, it's hard to tell at this point from the inflow/outflow data what we can really expect in the coming weeks. The average "hit bottom" date historically is April 22, but that date has a huge variation, and it's hard to draw conclusions from that date as to what might happen ahead. This year, with outflows being held back a bit compared to recent years, it might be that the turnaround date does come a bit early. Last year, it wasn't until late May. The year before, it was early May. Same with 2018. All three were bad runoff years. The trend, in general, for the "better than average" years is when the lake starts turning around by mid-April. That was the case for 2011, 2014 and 2019. But who knows?

I'd watch the inflows closely. Right now they are still hovering in the 6-8,000 cfs range. Historically on average, by early April those flows are closer to 10,000 cfs. Last year we were still in the 4-6,000 cfs range at this point, so I'm thinking we're going to do better than that. But actually, with the exception of the really wet years of 2011 and 2017, we're really in the same inflow ballpark as almost every other year back to 2009. Let's look at the data in another week or two and reassess then.

Here's what I'm looking for--what is the first date that inflow hits 30,000 cfs? That's the marker of what kind of rise we can really expect. Most years (all but 11) have reached that milestone, and usually by the end of May. But if we don't hit that (as we didn't last year), it's a bad year. In a "slightly better than average" year where total annual inflow is in the 9-9.5 maf (like 2014-16), look for the 30K cfs inflow milestone to be reached in mid- to late May.

And then in the better years, we'll hit a 50K cfs milestone, usually in late May or early June. Historically, it's about a 50-50 chance in any given year of hitting 50k cfs...but when it does, it's always a sign of a good year. The last year that happened was in 2019, when runoff peaked at 78k cfs on June 18.

Again, it's still a little too early to tell what to expect...

Great input JFRC! I try to always make it known when replying to a majority of these "water data" posts that I am NOT an expert by any means...I do learn quite a bit, which is a plus. However....with your input, wouldn't the affected reservoirs above Powell, such as Blue Mesa and Navajo, effect what the runoff will REALLY be? Meaning, since they have been dramatically impacted these last few years, maybe they allow those to recover a little which could impact flow into Powell? Just a thought.

 

[JFRCalifornia]

Great input JFRC! I try to always make it known when replying to a majority of these "water data" posts that I am NOT an expert by any means...I do learn quite a bit, which is a plus. However....with your input, wouldn't the affected reservoirs above Powell, such as Blue Mesa and Navajo, effect what the runoff will REALLY be? Meaning, since they have been dramatically impacted these last few years, maybe they allow those to recover a little which could impact flow into Powell? Just a thought.

Well, it does make a difference as to how much is held back in the reservoirs above Lake Powell, but in the big picture, only what they do at Flaming Gorge (and to a much lesser extent, Navajo) makes a significant difference. Collectively, the reservoirs above Powell have a capacity of about 6.4 maf, and right now they are holding a little over 4 maf, or about 65% of their collective capacity. Three fourths of that volume is sitting in Flaming Gorge. Navajo is hanging in there at about 50% of its capacity (0.8 maf out of 1.6 maf possible), but in the big picture, this doesn't make a huge difference as to what happens downstream. And Blue Mesa is almost a relative drop in the bucket. Even though it's less than 30% full, it only has a capacity of 0.8 maf, so even filling it all the way only holds back a little over 0.5 maf.

Yes, filling the upstream reservoirs is a way BOR might hold back inflow to Powell, but the snowpack makes a much bigger difference as to what happens... That, along with how much water is diverted for Upper Basin use before it ever reaches as far as Powell...

 

[Piece-O-Crappie]

More great input JFRC! Thanks!

 

[nzaugg]

Well, it does make a difference as to how much is held back in the reservoirs above Lake Powell, but in the big picture, only what they do at Flaming Gorge (and to a much lesser extent, Navajo) makes a significant difference. Collectively, the reservoirs above Powell have a capacity of about 6.4 maf, and right now they are holding a little over 4 maf, or about 65% of their collective capacity. Three fourths of that volume is sitting in Flaming Gorge. Navajo is hanging in there at about 50% of its capacity (0.8 maf out of 1.6 maf possible), but in the big picture, this doesn't make a huge difference as to what happens downstream. And Blue Mesa is almost a relative drop in the bucket. Even though it's less than 30% full, it only has a capacity of 0.8 maf, so even filling it all the way only holds back a little over 0.5 maf.

Yes, filling the upstream reservoirs is a way BOR might hold back inflow to Powell, but the snowpack makes a much bigger difference as to what happens... That, along with how much water is diverted for Upper Basin use before it ever reaches as far as Powell...

The teacup diagram also shows Flaming Gorge is 78% full, down 0.75 MAF, so there is not much recovery necessary there. BOR is likely to prioritize keeping Glen Canyon power generation online through the summer demand period, which may result in some hold back, resulting in 3525 being breached sometime in October according to the most probable projection.

 

[JFRCalifornia]

The Great Water Transfer... from 2014.. may have changed ?​

Colorado has 44 trans basin diversions, 27 of which cross the Continental Divide. Water that crosses the Divide disappears from its original basin... water that no longer goes to Lake Powell.

The Great Water Transfer

Diverting Water from Basin to Basin In the summer of 1860, farmers in central Colorado found Left Hand Creek dry. They started looking for replacement water. Just over the ridge, South St. Vrain Creek flowed wet, so they dug a ditch to divert its water back to Left Hand Creek. This solved their...

westernconfluence.org

An interesting article, and even though it's from 2014, it's still relevant. But it, like many similar stories floating out there, includes some misleading information about how much can be diverted above Lees Ferry for Upper Basin use. Here's a quote from the article:

"Depending on conditions, Wyoming gets roughly 1.04 million acre-feet, about 250,000 of which are currently not being used."

The implication of that is that Wyoming has some sort of unused water supply potential from the Colorado River. Not quite correct. Wyoming, like all three other Upper Basin states, gets to divert surplus supply once water is delivered to the Lower Basin and Mexico. In the case of Wyoming, it's 14% of the leftover, if any. And yes, 14% of 7.5 maf (the Upper Basin's maximum theoretical share) is about 1.05 maf. But 14% of zero is zero.

The problem in the water math under the Compact is that Upper Basin diversions happen before really knowing if there's enough water to deliver to the Lower Basin. Until recent years, it was never a practical problem, because once the Lower Basin deliveries were made, and the Upper Basin took what it needed, the leftover in effect is what sat in Lake Powell. And that seemed to work okay when the lake had a lot of water. Who cared if the Upper Basin used more than it's theoretical share? It was hard to calculate anyway, since available "share" could not be known until after the fact. But since Lake Powell is the Upper Basin's "bank", and the bank has steadily been losing "funds" in recent years, you know right there that the Upper Basin, for all its good intentions, has been using more than allowed under the Compact, because if it were coloring within the lines (as written), Lake Powell would be at a more or less steady state. And since much of that Upper Basin diversion is an interbasin transfer outside the Colorado/Green watershed, return flow never makes it back to Powell and beyond. Not casting blame here, just stating the facts.

Of course, now when the water is low at Powell is the time when it will start to get "interesting". That's because BOR is still required to make those Lower Basin deliveries, and it really wants (needs?) to maintain Powell high enough to generate power. So that means unless the snowpack regime changes dramatically for the better over the next few years, this is the first time the system will ever have been put to the test in terms of really accounting for the Upper Basin's water use. As it is right now, there is no BOR-organized collective Upper Basin water use reporting system as there is for the Lower Basin. That's one reason many point the finger at the Upper Basin, whether fair or not. There's certainly excellent local accounting above Lake Powell, whether by state, county or water district, but there's no one place or report you can find to see what it all adds up to and whether it leads to an unsustainable water supply system in the Colorado/Green River basin. That's certainly one issue (among many) that will need to be addressed in a reworking of the 1922 Compact...

 

[Dorado]

An interesting article, and even though it's from 2014, it's still relevant. But it, like many similar stories floating out there, includes some misleading information about how much can be diverted above Lees Ferry for Upper Basin use. Here's a quote from the article:

"Depending on conditions, Wyoming gets roughly 1.04 million acre-feet, about 250,000 of which are currently not being used."

The implication of that is that Wyoming has some sort of unused water supply potential from the Colorado River. Not quite correct. Wyoming, like all three other Upper Basin states, gets to divert surplus supply once water is delivered to the Lower Basin and Mexico. In the case of Wyoming, it's 14% of the leftover, if any. And yes, 14% of 7.5 maf (the Upper Basin's maximum theoretical share) is about 1.05 maf. But 14% of zero is zero.

The problem in the water math under the Compact is that Upper Basin diversions happen before really knowing if there's enough water to deliver to the Lower Basin. Until recent years, it was never a practical problem, because once the Lower Basin deliveries were made, and the Upper Basin took what it needed, the leftover in effect is what sat in Lake Powell. And that seemed to work okay when the lake had a lot of water. Who cared if the Upper Basin used more than it's theoretical share? It was hard to calculate anyway, since available "share" could not be known until after the fact. But since Lake Powell is the Upper Basin's "bank", and the bank has steadily been losing "funds" in recent years, you know right there that the Upper Basin, for all its good intentions, has been using more than allowed under the Compact, because if it were coloring within the lines (as written), Lake Powell would be at a more or less steady state. And since much of that Upper Basin diversion is an interbasin transfer outside the Colorado/Green watershed, return flow never makes it back to Powell and beyond. Not casting blame here, just stating the facts.

Of course, now when the water is low at Powell is the time when it will start to get "interesting". That's because BOR is still required to make those Lower Basin deliveries, and it really wants (needs?) to maintain Powell high enough to generate power. So that means unless the snowpack regime changes dramatically for the better over the next few years, this is the first time the system will ever have been put to the test in terms of really accounting for the Upper Basin's water use. As it is right now, there is no BOR-organized collective Upper Basin water use reporting system as there is for the Lower Basin. That's one reason many point the finger at the Upper Basin, whether fair or not. There's certainly excellent local accounting above Lake Powell, whether by state, county or water district, but there's no one place or report you can find to see what it all adds up to and whether it leads to an unsustainable water supply system in the Colorado/Green River basin. That's certainly one issue (among many) that will need to be addressed in a reworking of the 1922 Compact...

Another factor is that upper basin states, like Wyoming, continue to press forward with "water development" projects that have no economically viable reason to exist. Their purpose is to stake a claim on the "unused" water and give them more leverage when the 1922 Compact is reassessed. I attended a meeting several years ago on the seemingly un-killable proposal to create a reservoir on the Green River north of Pinedale. This project has been put forward and rejected repeatedly...because it makes no sense! It would flood the migration corridor of the longest and largest ungulate migration in North America, and only serve a few hay farmers in the region. Several of the proponents at the meeting earnestly put forward that the only real roadblock to the project was the cost/benefit analysis that indicated it is a giant boondoggle! Since they were not paying for it personally, they were all for it.
Sorry for the rant, but we are not going to "develop" our way out of this mess!

 

[ndscott50]

"Depending on conditions, Wyoming gets roughly 1.04 million acre-feet, about 250,000 of which are currently not being used."

The implication of that is that Wyoming has some sort of unused water supply potential from the Colorado River. Not quite correct. Wyoming, like all three other Upper Basin states, gets to divert surplus supply once water is delivered to the Lower Basin and Mexico. In the case of Wyoming, it's 14% of the leftover, if any. And yes, 14% of 7.5 maf (the Upper Basin's maximum theoretical share) is about 1.05 maf. But 14% of zero is zero.

We really need to accelerate the process to create a new Colorado River compact because the current one is likely unenforceable if drought conditions continue. As you point out, by the law the lower basin states could demand the upper basin states use zero water from the Colorado if they are unable to deliver the 7.5 maf to the lower basin states. The upper basin states will never agree with that and would likely actively resist any attempt to implement it - they have the advantage that the water starts in their states. I am doubtful the upper basin states will even agree to significant cuts in usage without corresponding cuts in the lower basin states. The administration and congress are not going to get behind enforcing such a one sided outcome. California can argue that it has a right to Colorado River water before anyone else but if there is no one to enforce it that right is meaningless.

There is really only one solution. Each state gets a percentage of the total water available. Each year (or over some number of years) based on river flow and storage you determine total water available and then each state applies their percentage to that to determine what they can use. If the total water available is down 20% then each state has to cut their usage 20%.

 

[JFRCalifornia]

There is really only one solution. Each state gets a percentage of the total water available. Each year (or over some number of years) based on river flow and storage you determine total water available and then each state applies their percentage to that to determine what they can use. If the total water available is down 20% then each state has to cut their usage 20%.

Seems reasonable, and has the virtue of simplicity. The tricky part is determining the percentage allocation that would be fair. Should it be the current amounts (for the Lower Basin) converted to percentages, and assume a full allocation for the Upper Basin? In that case, it would be:

CA - 29.3%
AZ - 18.7%
NV - 2.0%
CO - 25.9%
UT - 11.5%
NM - 5.6%
WY - 7.0%

Or should it be based on state population? Or population within the watershed area for each state (which would greatly reduce the amount for CA and CO in particular)? Or cultivated farmland in the watershed? Or historic water use in the past 10 years (which would be ideal for the growing Upper Basin states)? Or some combination? And what about Mexico? This will be a fight.

But no matter how you slice it, the amount available for the following year should be based on a rolling 10-year average inflow for the previous ten years, or something similar to disincentivize overuse and smooth out spikes that appear in trends. But where do you measure inflow to make that determination? If it's into Lake Powell, then that allows the Upper Basin states to get an unfair upper hand, because their withdrawals would occur before that point, and thus not be considered in the rolling inflow 10-year average. How do you account for that?

Many threads to untangle, but before even considering those, first you have to untie the knot of existing water rights. How do you compensate states that will lose a portion of their existing rights, particularly CA? Do other states help subsidize the construction of water desalination plants on the CA coast in exchange for some of CA's water rights loss? What about AZ? Or other inland states that might "lose" rights? Do the other states help fund wastewater reclamation facilities in those states to offset their water loss? And if so, where is all the money coming from? There needs to be a revenue generation source for this to work for everyone. Recreation and tourist dollars might be part of the answer. Or money raised from power generation. So would reallocation of part of the federal or affected state budgets.

There will be losers in this, but I'm not sure there will be any obvious winners. Except perhaps the river, the reservoirs on the river, and those who depend on those for power, recreation and the benefits of the resources they provide.

This will be an enlightening process, but it will depend on mutual trust and cooperation among the states, not something they are necessarily known for. But it's the only way.

 

[boatdaddy]

JFRCalifornia, would a five-year rolling average be a better indication of conditions as this much lower snowpack, inflow seems to be accelerating at a faster pace?

I'm here to learn and this forum is really helping me understand the multiple issues.

 

[JFRCalifornia]

JFRCalifornia, would a five-year rolling average be a better indication of conditions as this much lower snowpack, inflow seems to be accelerating at a faster pace?

I'm here to learn and this forum is really helping me understand the multiple issues.

It's true that a 10-year average is somewhat arbitrary, but when you look at the numbers, a 5-year average doesn't yield a much different result. Here's what you get for a rolling average inflow for the past decade. The first number is the 5-year rolling average inflow, while the second number is the 10-year average:

Year - 5 yr avg/10 yr avg (maf)

2012 - 10.7/9.4
2013 - 9.3/9.3
2014 - 9.1/9.6
2015 - 9.2/9.4
2016 - 8.0/9.5
2017 - 9.0/9.9
2018 - 9.1/9.2
2019 - 9.5/9.3
2020 - 9.0/9.1
2021 - 7.8/7.9

The numbers are close, with the main difference being slightly more variability in the 5-year average, as you'd expect. From a planning standpoint, it's easier to plan ahead when the yearly variation is less, and that begs using the 10-year average method. The longer timeframe also captures drought years (or good years) over a decade, which is important, because if there's one thing that Lake Powell has shown us, is that a great year can follow a terrible one, or vice versa. You need a longer timeframe to capture that variability. But sure, it's a discussion to have.

The bigger problem no matter the method is that these inflow numbers already account for the fact that the Upper Basin has taken its share before the water reaches Lake Powell. That is, the inflow would be even higher if the Upper Basin took nothing. That's a huge deal. And in past decades, the Upper Basin did indeed take less (because they needed less, or chose not to assert a need), which is one reason why you see the inflow numbers going into Lake Powell steadily creeping downward over the years. It's not just reduced snowpack or increased evaporation--it's also increased Upper Basin diversions, don't forget that... And that has to be factored into any method used...

 

[boatdaddy]

Thanks for the facts behind the numbers. I do agree that upper basin diversions as well as lower basin diversions are increasing with new communities being developed. More drawn downs adding to the limited resources.

Mid May is usually the last date that we see snow in metro Denver, while the mountains can get snow at any time. I hope we get some of those late snow falls this year.

 

[Paladin]

Seems reasonable, and has the virtue of simplicity. The tricky part is determining the percentage allocation that would be fair. Should it be the current amounts (for the Lower Basin) converted to percentages, and assume a full allocation for the Upper Basin? In that case, it would be:

CA - 29.3%
AZ - 18.7%
NV - 2.0%
CO - 25.9%
UT - 11.5%
NM - 5.6%
WY - 7.0%

Or should it be based on state population? Or population within the watershed area for each state (which would greatly reduce the amount for CA and CO in particular)? Or cultivated farmland in the watershed? Or historic water use in the past 10 years (which would be ideal for the growing Upper Basin states)? Or some combination? And what about Mexico? This will be a fight.

But no matter how you slice it, the amount available for the following year should be based on a rolling 10-year average inflow for the previous ten years, or something similar to disincentivize overuse and smooth out spikes that appear in trends. But where do you measure inflow to make that determination? If it's into Lake Powell, then that allows the Upper Basin states to get an unfair upper hand, because their withdrawals would occur before that point, and thus not be considered in the rolling inflow 10-year average. How do you account for that?

Many threads to untangle, but before even considering those, first you have to untie the knot of existing water rights. How do you compensate states that will lose a portion of their existing rights, particularly CA? Do other states help subsidize the construction of water desalination plants on the CA coast in exchange for some of CA's water rights loss? What about AZ? Or other inland states that might "lose" rights? Do the other states help fund wastewater reclamation facilities in those states to offset their water loss? And if so, where is all the money coming from? There needs to be a revenue generation source for this to work for everyone. Recreation and tourist dollars might be part of the answer. Or money raised from power generation. So would reallocation of part of the federal or affected state budgets.

There will be losers in this, but I'm not sure there will be any obvious winners. Except perhaps the river, the reservoirs on the river, and those who depend on those for power, recreation and the benefits of the resources they provide.

This will be an enlightening process, but it will depend on mutual trust and cooperation among the states, not something they are necessarily known for. But it's the only way.

Well done and well stated.
All negotiations will involve, as you say, "compensation." There is a lot of talk in this thread of cost/benefit analytics. For me its hard to contrast hay farmers on the Green with Douglas County (actually on the Eastern Slope) development with an SFR in San Diego and strawberry growers in the Imperial Valley.

Sooo... have you done any true analyses of the actual cost (or inherent value) of wet water as it comes out of Glen Canyon Dam? I ask this because of your statement "revenue generation source." As you know by now, part of my interest in keeping adequate water in Lake Powell is for the benefit of the rights of recreational users. Same with other lakes (reservoirs). But it is critical to be a part of the solution and not give rise to the growing problems. At $580 million annually, and a an economic multiplier of 10, how does this contrast to actual value of released wet water? I know some of this is apples vs. oranges, but its a start. I look at it as lateral economic integration. Generating cash from something that is already there, something that goes by and is lost forever and generating some bucks in a non-consumptive way could be part of the solution.

I know that cash generated at GCRA is not fungible but I'll throw it on the table for discussion.

Again, what do your analytics tell you is the actual cash value of stored and released water to the Lower Basin?

 

[ndscott50]

I played with some numbers to look at future scenarios for the Colorado River Compact.

First as JFR stated the 10-year average inflow into Powell is currently 7.9maf. The five-year average for consumption above Powell (I could not find a 10-year numbers) is 4.6maf. This gives total water available of 12.5maf. This is 4maf below the compact assumption of 16.5maf. There is some inflow below Powell, but I am going to ignore that to keep things a little easier.

Option one would be to use the current percentages allocated to each state based on 16.5maf per year and apply that to the 12.5maf that actually exist. This would provide each state with the following relative to their current (five-year average) consumption of CO river water. Values are in thousands of acre feet of water

	Change in Current	Percent Change in Current
CO	425	17%
UT	204	19%
WY	297	60%
NM	138	28%
AZ	-339	-14%
CA	-721	-18%
NV	-28	-11%
MX	-362	-24%

Obviously, the upper basin states would be a big fan of this plan and WY and NM would likely be looking to sell some water rights to nearby states. CA is not going to be down with cutting their current usage by 18% while Colorado gets to grow its usage by 17%.

On the opposite end of the spectrum would be to use the amount of water each state currently uses to establish each states share and then apply that percentage to the actual water available.

CO	-75	-3%
UT	-33	-3%
WY	-15	-3%
NM	-15	-3%
AZ	-75	-3%
CA	-121	-3%
NV	-8	-3%
MX	-45	-3%

While this shares the pain the upper basin states would strongly object that this limits their growth and maintains a system that allocates an unfair amount of water to the lower basin. The answer is probably in-between these two approaches, but it will be a nasty fight.

One more wrinkle to add would be that this approach uses all the water available, and Mead/Powell is only at 28% of capacity. If we reserved 10% of the water available, 1.25maf per year to rebuild storage, it would take us 8.5 years to bring the Mead/Powell system up to 50% of capacity (assuming the average holds over that time). That would increase the cuts needed by a good deal. Using scenario 1 with the reservoir reserve, the changes in each states current consumption would be:

CO	5%
UT	7%
WY	44%
NM	15%
AZ	-22%
CA	-26%
NV	-20%
MX	-32%

Under the second scenario each state would have to cut its current consumption by 12.7%.

 

[Colorado Expat]

Coex -- so does such rain reduce the inflow (all else being equal)? We have seen how warm spring winds will decimate snowpack and runoff/inflow. However, if next week's system drops, say, a half inch of rain across the basin rather than the equivalent snow, will there be less, more or about the same inflow for the season?

Trix - I didn't mean to ignore your question here, I just got really busy at work and had to step away from fun stuff like this forum.

In a nutshell, rain and snow are both just water inputs on the landscape, the difference being that the former runs off or sinks in more quickly than the latter. And if rain falls on snow, it will tend to melt the snow, since the temperature of the raindrops is above freezing. All that means is that you get a more episodic pulse of runoff, rather than a longer and more continuous release. So if we now transition to spring rain it will simply produce the same amount of runoff as would have happened in any case, but compressed into a potentially shorter time frame.

Ranchers and other folks in the Upper Basin prefer it when there is a good sized snowpack that melts gradually and not too early, because it provides them with a steady supply of water in the drier summer months for things like growing hay and watering livestock. The fact that we may be topping out early this year and already starting the runoff stage does not bode well for drought status or wildfire risk in Colorado later this summer. The Colorado River discharge at the Cisco gauge has doubled over the past 3 weeks, from 2000 to 4000 cfs, and since there is no storage on the main stem below Lake Granby, and the reservoirs on the Gunnison are already depleted and not releasing extra, that reflects mostly melt from the unusual warm spell two weeks ago. With another 3-4 days of warm temperatures now on the way due to ridging over the West, this melting trend, which had temporarily paused, will likely resume.

 

[Colorado Expat]

Straight from a NOAA briefing earlier this morning, the most recent runoff volume forecast for the upper Colorado River system.



Bottom line is that the current prediction is for Lake Powell to receive 64% of 1991-2020 average runoff volume. NOAA also noted that poor March snowfall and continuing low soil moisture conditions in western Colorado are contributing to this reduction in predicted runoff. I leave it to the number gurus like JFR to figure out what this really means in terms of likely lake levels going forward. The NOAA prediction is just for runoff, and would not factor in any supplemental release from Flaming Gorge to keep Lake Powell above minimum hydro pool.

 

[ndscott50]

Straight from a NOAA briefing earlier this morning, the most recent runoff volume forecast for the upper Colorado River system.

View attachment 17822

Bottom line is that the current prediction is for Lake Powell to receive 64% of 1991-2020 average runoff volume. NOAA also noted that poor March snowfall and continuing low soil moisture conditions in western Colorado are contributing to this reduction in predicted runoff. I leave it to the number gurus like JFR to figure out what the really means in terms of likely lake levels going forward. The NOAA prediction is just for runoff, and would not factor in any supplemental release from Flaming Gorge to keep Lake Powell above minimum hydro pool.

I believe 64% of average runoff is 4.12-million-acre feet (maf). The release schedule for that period (April to July) is 2.58 maf so the lake will net 1.54 maf. We are currently at 5.8 maf so that puts us at 7.3 maf of storage on July 30th. The last time the lake was at 7.3 maf of storage was September 26th and the lake level was 3,546. You also get some evaporation so something lower than that for the final rise (3,542?). Call it 20 foot rise this spring.

Hopefully we get some more snow in April so the forecast holds. Last year at this time the forecast was for 3.2 maf of runoff and we ended up with only 1.8 maf (April was a disaster). The current weather of sunny and the wind howling is unfortunately great for sublimation.

 

[Colorado Expat]

Another real irony here is that Flaming Gorge is the one Upper Basin storage unit that is still in moderately good shape, at 78 percent of full pool, and thus might have some ability to send a bit more water downstream later in the summer to stabilize hydro at Powell. But in this current forecast, the upper Green River has the worst runoff projection of any of the upstream sub-basins, due to poor snowfall there from January through March. That will make it harder for BOR to spill water from there without putting that lake in trouble as well, since it also has a hydro plant with some minimum lake elevation necessary to operate.

 

[JFRCalifornia]

I believe 64% of average runoff is 4.12-million-acre feet (maf). The release schedule for that period (April to July) is 2.58 maf so the lake will net 1.54 maf. We are currently at 5.8 maf so that puts us at 7.3 maf of storage on July 30th. The last time the lake was at 7.3 maf of storage was September 26th and the lake level was 3,546. You also get some evaporation so something lower than that for the final rise (3,542?). Call it 20 foot rise this spring.

Hopefully we get some more snow in April so the forecast holds. Last year at this time the forecast was for 3.2 maf of runoff and we ended up with only 1.8 maf (April was a disaster). The current weather of sunny and the wind howling is unfortunately great for sublimation.

That's a fair analysis, much appreciated. That said, my numbers come out a little differently, and don't paint quite as optimistic a picture, although it's in the same ballpark.

My first thought is this: does the 64% runoff mean April to July, or April through July? It makes a difference, although not a big one. I think ndscott50 assumed April through July, and so here's how I see it for the same period. I agree the release schedule is 2.58 maf through that period. But the average Apr 1-Jul 31 inflow (based on the WaterDatabase) from 1991-2010 is 5.63 maf (this compares to 5.97 maf from 1965-2021). That means 64% of that 1991-2020 average is 3.60 maf, not 4.12 maf. So I calculate the net inflow as 1.02 maf, not 1.54 maf. If my numbers are right (and they could be wrong), that translates to a July 31 volume of 6.83 maf (it was 5.81 maf on April 1). And if that's true, the lake level on that date would be 3539, not 3546. Evaporation might drop that a hair. Not a huge difference, but worth noting given where the lake stands right now.

Summary:

April 1-July 31 (assumes 64% of 1991-2020 inflow)

Inflow - 3.60 maf
Outflow - 2.58 maf

Net Inflow - 1.02 maf
July 31 volume - 6.83 maf
July 31 lake level - 3539

Someone please check my analysis, and I hope I'm wrong.

Now if the forecast instead was 64% of April to July, that changes things a bit, but not much. Here's the summary of that analysis:

April 1-June 30 (assumes 64% of 1991-2020 inflow)

Inflow - 2.95 maf
Outflow - 1.78 maf

Net Inflow - 1.17 maf
June 30 volume - 6.98 maf
June 30 lake level - 3541

Bottom line is to expect to hover around 3540 in mid-summer, assuming all the above assumptions are correct.

To provide some points of comparison, here's what the April 1 - July 31 gross inflow was in recent years:

2016 - 6.0 maf
2017 - 7.4 maf
2018 - 2.3 maf
2019 - 8.5 maf
2020 - 3.4 maf
2021 - 1.7 maf
2022 - 3.6 maf (????)

Remember, the all-time average is 5.97 maf, and the 1991-2020 average is 5.63 maf. If we really end up with 3.60 maf, that's a little better than 2020, or something like 2003 or 2007 for those who remember those unremarkable, somewhat below average years. And yes, the 2021 number was the worst in the lake's history. On the flip side, in the really huge years of 1983 and 1984, that number was about 13.5+/- maf...

 

[Colorado Expat]

JFR - For the purposes of today's NOAA briefing, the percentage for each basin represents expected runoff from April 1 through July 30 as a percentage of the 1991-2020 average. So that would equate to your calculated net inflow of 1.02 maf.

The link to the entire briefing presentation is here: https://www.cbrfc.noaa.gov/present/2022/cowsupapr2022.pdf

 

[Bullfrog1987]

JFR, thank you for your thoughtful analysis and taking the time to share it with us. I am a LONG time lurker on this site and have learned a lot from everyone who shares their thoughts and opinions here. I have spent a lot of time at the lake, have experienced both wonderful and terrifying times there over the years. Countless trips with former and current friends, family, and many that are no longer with us. Wonderful memories. I hope that your analysis of the water level is correct, I have a week long trip set for early July and it seems that if your analysis is correct I will have the opportunity to make some more memories !