Past the peak and a post-mortem...

D

DVexile

Active Member
Technically the fat lady has not left the stage, but unless she goes off script from the libretto, that was in fact the peak a few days ago. There was some hope that the Flaming Gorge release might bump the lake up a bit higher than it got on June 18th, but it appears that will not happen:

GLDA3_hydrograph-2.png
Here is the forecast inflow for the next few days. If we integrate up everything in the curve we get a rise of just 0.06 foot from where we sit today. And today we are already 0.09 foot below the June 18th peak. So we will see a second little bump and the Flaming Gorge release will stave off the decline for a few more days creating a broader peak than we would have had otherwise, but the lake won't get any higher than it was on the 18th. And by the Fourth of July we will be falling by about 0.15 foot per day.

Of course these discussions of things less than 0.1 feet means we are literally talking about lake elevations changes of around one inch! How many angels on the head of pin kind of stuff. It isn't a good year, that's the take away.

Steadily underperforming the forecasts...

This chart tells the story pretty well:

GLDA3_espgraph.png


The February, March, and April official most probable inflow forecasts (April-Jul) were all 4300 kaf. In early April the unofficial daily most probable forecast got as high as 4688 kaf. Today's estimate is 2778 kaf, or only about 65% of the official forecast in April.

But it is important to remember just how much uncertainty there are in these forecasts and this is reflected in the forecasts themselves. It is natural to feel that in April we should have a pretty good handle on how good a year we are going to have, after all the snowpack is at its peak by the start of April! But the runoff isn't all about just the snowpack.

In April with 10-90% forecast range was 3150 kaf to 6600 kaf. That's a huge range! It's equivalent to almost 50 feet of lake elevation! And remember, we should expect to fall outside that range in one out of every five years! That's worth stating again in bold I think:

Even when the peak snowpack is known exactly there is still at least 50 feet of lake elevation of uncertainty in the runoff forecasting!!!

Well, this was one of the ten years we'd expect to fall outside the lowest range of estimates made in April. On April 1 the low end was 3150 kaf and right now it looks like we will get around 2800 kaf. That's about five feet of lake elevation below the "minimum probable" back in April. Even with that 50 foot range we fell another five feet outside it!

It's been interesting!

Anyway, I became morbidly interested in this year's runoff a few months ago when I became curious about what was going to make this year different from the dread 2021. That year had a big forecast miss as well. This year the snow pack was similar and the climate was quite dry, but in theory the forecasting tools know that better than me! So I've been entertaining myself, and hopefully at least a few people here at the same time, crunching some numbers and watching how things developed.

Certainly while 2024-25 was dry and warm and caused a lot of snow to never make it to the lake as runoff it wasn't nearly as dry and warm as 2020-21. So thankfully this year wasn't nearly as bad and shouldn't have been expected to be as bad. If we'd had a repeat of 2021 we'd be about another 13 feet lower than we are!

But I am super curious now about what all gets integrated into the forecast tools. Until I started paying attention to this I didn't fully appreciate just how little we actually know even when we have perfect information on the snow pack. I presume a lot of the soil and vegetation water deficits are included in the forecast tools, but either I'm wrong about that, or those estimates are still very uncertain, or there is still a huge impact of weather after April that can cause such a wide range of outcomes.

Fingers crossed next year is a lot better for the lake!
 
Start with the base ground moisture levels. Then no matter how many sensor stations you have set up it doesn't give the complete picture of how much moisture is really up there, plus all the variables in how much water is being pumped or diverted. Add to that the facts that a few good rain storms or dry wind/heat events can make a large difference it's just a very chaotic system.
 
I was reading an article about the greater Yellowstone area where I live, but the same can be said for the Colorado river basin. It was saying that the super dry and warm fall early winter we experienced last year set us up for low stream flows and early forest fires this year. Basically going into the wet period of spring with a water deficit. Unfortunately, warm, dry fall weather (which seems to be the norm these days) makes it difficult to stay out of drought, even when we have a decent or wet winter snow pack.
 
DVexile said:
Technically the fat lady has not left the stage, but unless she goes off script from the libretto, that was in fact the peak a few days ago. There was some hope that the Flaming Gorge release might bump the lake up a bit higher than it got on June 18th, but it appears that will not happen:

View attachment 33066
Here is the forecast inflow for the next few days. If we integrate up everything in the curve we get a rise of just 0.06 foot from where we sit today. And today we are already 0.09 foot below the June 18th peak. So we will see a second little bump and the Flaming Gorge release will stave off the decline for a few more days creating a broader peak than we would have had otherwise, but the lake won't get any higher than it was on the 18th. And by the Fourth of July we will be falling by about 0.15 foot per day.

Of course these discussions of things less than 0.1 feet means we are literally talking about lake elevations changes of around one inch! How many angels on the head of pin kind of stuff. It isn't a good year, that's the take away.

Steadily underperforming the forecasts...

This chart tells the story pretty well:

View attachment 33067


The February, March, and April official most probable inflow forecasts (April-Jul) were all 4300 kaf. In early April the unofficial daily most probable forecast got as high as 4688 kaf. Today's estimate is 2778 kaf, or only about 65% of the official forecast in April.

But it is important to remember just how much uncertainty there are in these forecasts and this is reflected in the forecasts themselves. It is natural to feel that in April we should have a pretty good handle on how good a year we are going to have, after all the snowpack is at its peak by the start of April! But the runoff isn't all about just the snowpack.

In April with 10-90% forecast range was 3150 kaf to 6600 kaf. That's a huge range! It's equivalent to almost 50 feet of lake elevation! And remember, we should expect to fall outside that range in one out of every five years! That's worth stating again in bold I think:

Even when the peak snowpack is known exactly there is still at least 50 feet of lake elevation of uncertainty in the runoff forecasting!!!

Well, this was one of the ten years we'd expect to fall outside the lowest range of estimates made in April. On April 1 the low end was 3150 kaf and right now it looks like we will get around 2800 kaf. That's about five feet of lake elevation below the "minimum probable" back in April. Even with that 50 foot range we fell another five feet outside it!

It's been interesting!

Anyway, I became morbidly interested in this year's runoff a few months ago when I became curious about what was going to make this year different from the dread 2021. That year had a big forecast miss as well. This year the snow pack was similar and the climate was quite dry, but in theory the forecasting tools know that better than me! So I've been entertaining myself, and hopefully at least a few people here at the same time, crunching some numbers and watching how things developed.

Certainly while 2024-25 was dry and warm and caused a lot of snow to never make it to the lake as runoff it wasn't nearly as dry and warm as 2020-21. So thankfully this year wasn't nearly as bad and shouldn't have been expected to be as bad. If we'd had a repeat of 2021 we'd be about another 13 feet lower than we are!

But I am super curious now about what all gets integrated into the forecast tools. Until I started paying attention to this I didn't fully appreciate just how little we actually know even when we have perfect information on the snow pack. I presume a lot of the soil and vegetation water deficits are included in the forecast tools, but either I'm wrong about that, or those estimates are still very uncertain, or there is still a huge impact of weather after April that can cause such a wide range of outcomes.

Fingers crossed next year is a lot better for the lake!
Click to expand...
Excellent post and great expansive 'wet' fud for thought.... (y)

Also hadn't heard the term 'libretto' in many a moon....;) (y)

mcpltret was wondering if the fat lady's libretto was somehow connected to her libido....:unsure:

:cool:
 
It is not just a warm, dry fall that impacted subsequent spring runoff in 2025, it is the overall trend of air temperatures running above average in all seasons, as seen on this graphic for Colorado, where the majority of runoff into Lake Powell comes from.

Colorado Averate Temp Rank.png

And this year was not just a one-off. The underlying temperature baseline has been steadily rising for the past 50 years, and this shows no sign of abating, as this plot illustrates.

Global Temp Anomaly 1850-2024.png

Under such a regime of steadily rising air temperatures the vapor pressure deficit is not our friend, since the warmer atmosphere is capable of extracting progressively more water from soils and vegetation. Therefore, in the future, we will need above average snowfall every winter in order to maintain even average runoff based on past statistics. That clearly is not going to happen, since we will be running harder and harder just to stay in place like the Red Queen in Alice in Wonderland. So what we are faced with realistically is a steady decline in baseline river discharge, albeit with some years better than others.

All the above points were laid out quite clearly by Brad Udall of Colorado State University at the recent Colorado River Conference in Boulder, and his remarks, which can be found online, are very much worth reading. His view is that there is a good likelihood of a future river where annual runoff amounts to about 10 million acre feet on an average year. If that comes to pass, it will make this year’s problems look trivial.
 
Simple answer. No more agriculture in the CO river drainage. The water will be sold to higher paying uses. And food will cost more
 
RiverRat68 said:
Push come to shove, agriculture should win out over all other uses...even power (build more nuke plants to compensate). Food ranks pretty high up on my list of necessities...and I'm not even involved in farming whatsoever.
Click to expand...
This line of reasoning has been discredited since 1817 (David Ricardo). Every nation state that has based resource planning on autarky has either failed or eventually given up on autarky and engaged in efficient trade like every other successful nation state.

Use your resources for what generates the greatest economic value, then trade for what you actually want or need. That’s why the US is the most powerful nation in the world - we’ve been doing that more successfully than most other nations.
 
Folks



One thing that impacts and reduces spring runoff is mid winter wind, hot wind to be more specific. Hot days will slowly melt the top snow layer with the layers below absorbing most of the water.



Hot wind will strip the top layer so fast you can literally watch the snow level drop. High wind with warm temps can turn a hill brown in no time. The hot dry wind has a lot of energy.



This past winter we had several weeks of very warm temps with very high winds at altitude.



The hot wind melt off this past Jan / Feb was sending more water direct into the sky than into the ground.



There is not a chance in hell that the lake will ever be intentionally drained, but there is a big chance it will drop to its emergency levels that force an agreement calibration to equal outflow to be less than in flow.



Call it what you want, things are in play that are delivering a different result. There is a pattern and the pattern is climate related. Focus on the pattern. Understand the pattern. Understand what causes the pattern. Understand what reverse or slows the pattern. Be curious.



Right now it is the extended periods of very warm high winds in the middle of the winter that is stripping the water right off the mountain. If you believe in science this is called sublimation - a very exciting process (google sublimation phase transition). If you do not believe in science, then it is magic, the snow just disappears.



There was a lot of snow in the Colorado range ready to flow to Powell that never turned to water, it got sucked into the sky as vapor. During hot windy winter months it may be possible the lake is losing more water to sublimation on the upper range than to absorption and evaporation.



I think the easiest way to get rid of the agreement is to simple let the lake get so low that no water can be released. Allow this forced natural condition to present an emergency opportunity to void the agreement. It will also be a good time to evaluate what is grown, I am all for being self sufficient, but lets be smart, lets buy crops from other areas that can grow them more efficiently and at a lower price. Let’s use our water for things that we cannot buy on the open market.




I would imagine that the USA makes more money in innovation technology and finance markets than in agriculture. Our exports are based on intellect not sun and water - it might be a good time to buy almonds from areas where they grow naturally, etc.




Folks, focus on the patterns and be curious.





.
 
bubba said:
One thing that impacts and reduces spring runoff is mid winter wind, hot wind to be more specific. Hot days will slowly melt the top snow layer with the layers below absorbing most of the water.
Click to expand...

Yep, evaporative potential is a huge component of drought. That’s a major reason why annual precipitation on its own is only a limited predictor of the type of biome in a region. And the evaporative potential in the CRB has most certainly increased and stayed high long enough to be creating big problems.

As far as short term forecasts (e.g. spring runoff forecast made in early spring) I’m curious how much of the large uncertainty is due to further sublimation or related evaporative potential affects occurring during the remainder of the spring.

In theory winter sublimation is accounted for by SWE sensors and surveys such that the April peak snowpack already accounts for what got lost in the winter. But as mentioned up above even in April the runoff forecast uncertainty is 50 feet of lake elevation!

To naive me there are potentially three or four different sources of spring forecast uncertainty in runoff loss:

1. Uncertainty in what future evaporative potential will be during the spring. This is the pretty obvious uncertainty of just not being able to predict the weather more than a week or so in advance. A hot windy spring is going to send lots of potential runoff into the atmosphere rather than the lake. This is “not knowing the future”.

2. Uncertainty in the soil water deficit at the time of the forecast. Some runoff is sucked up by desiccated soils as the snow melts and flows in drainages. Reading about the CRBFC forecasts it sounds like they are currently forced to measure and estimate soil water deficit in the fall due to limitations in sensors and surveys once temperatures drop to freezing. So in theory the same winter winds that sublimate snow can also further desiccate soils at lower elevations and maybe this is not well accounted for in the forecasts? This is “not knowing the present”. The deficit is already baked into the soil conditions but we just don’t have a good measure of what they are at the time of the forecast.

3a. Closely related to number 2 is uncertainty in vegetative water deficit, just how dry is the vegetation in the spring time and thus how much runoff will be lost to root systems desperately sucking up runoff water to make up that deficit. Another “not knowing the present”.

3b. Calling this 3b since it is so closely related to 3a, but I think worth distinguishing. Uncertainty in spring evapotranspiration, that is how much water travels through vegetation into the atmosphere as the result of plants using photosynthesis during spring growth. In theory if we get a sunny and warm spring that’s more ingredients for plant growth and thus more water lost to evapotranspiration. Also in theory if we add wind to the equation that removes even more water from growing plants since they will have stomata open for photosynthesis when conditions are favorable for growth. Wind when the plants are dormant with stomata closed would have less impact than when they are growing. This is mostly “not knowing the future” as it is about the coming spring growing season, but I suspect there is a “not knowing the present” component as well (see below).

Since I know next to nothing about how the forecasts work there are obviously other uncertainties I’m missing, but these seem to be the ones folks are talking about being related to recent changes in climate in the CRB. Thus these are factors related to a disconnect between SWE snowpack numbers and eventual inflows to the lake compared to past history.

It also sounds like the fact that these factors are now much more impactful to runoff means that they potentially play an increased role in forecast uncertainty or biases as we try to improve models and measurements related to them.

For example, apparently there is some SNOTEL data related to soil water deficit that isn’t included yet which might provide updated estimates through the winter. Also the soil models themselves are multi parameter complexities hand tuned with empirical data which makes me suspect their accuracy degrades significantly as conditions differ from historical regimes.

And it sounds like in the “not knowing the present” category there is uncertainty in just how much vegetation of various types there is and how exactly it behaves as far as evapotranspiration (in other words, even if we had perfect knowledge of future spring weather we couldn’t model how that would be reflected in evapotranspiration during spring growth).

The people who do the forecasting obviously know about all these uncertainties and presumably write about them and the efforts to improve upon them. I might try to learn more in the coming months if I can penetrate the literature without melting my brain.

Anyway, sorry for the more senseless pondering from the barely informed, but I guess the takeaway I’m trying to get to is:

Assume the more the climate deviates from historical norms the worse the seasonal forecasting will get.
 
Last edited:
DVexile said:
This line of reasoning has been discredited since 1817 (David Ricardo). Every nation state that has based resource planning on autarky has either failed or eventually given up on autarky and engaged in efficient trade like every other successful nation state.

Use your resources for what generates the greatest economic value, then trade for what you actually want or need. That’s why the US is the most powerful nation in the world - we’ve been doing that more successfully than most other nations.
Click to expand...
Many Thanks for that new (to moi) term... (y) Had to look it up: The word autarky is from the Ancient Greek word Greek: αὐτάρκεια, which means "self-sufficiency" (derived from αὐτο-, "self", and ἀρκέω, "to suffice").

So love the education here @ WW......(y)
 
DVexile said:
This line of reasoning has been discredited since 1817 (David Ricardo). Every nation state that has based resource planning on autarky has either failed or eventually given up on autarky and engaged in efficient trade like every other successful nation state.

Use your resources for what generates the greatest economic value, then trade for what you actually want or need. That’s why the US is the most powerful nation in the world - we’ve been doing that more successfully than most other nations.
Click to expand...
Yeah, I generally agree with you on this...For a scarce and critical resource, perhaps there should be room for greater control. My post really aims at arguments that say ag uses of CO water should be stopped or curtailed...and ag is the main reason the dams and reservoirs on the CO were built in the first place.
 
DVexile said:
Yep, evaporative potential is a huge component of drought. That’s a major reason why annual precipitation on its own is only a limited predictor of the type of biome in a region. And the evaporative potential in the CRB has most certainly increased and stayed high long enough to be creating big problems.

As far as short term forecasts (e.g. spring runoff forecast made in early spring) I’m curious how much of the large uncertainty is due to further sublimation or related evaporative potential affects occurring during the remainder of the spring.

In theory winter sublimation is accounted for by SWE sensors and surveys such that the April peak snowpack already accounts for what got lost in the winter. But as mentioned up above even in April the runoff forecast uncertainty is 50 feet of lake elevation!

To naive me there are potentially three or four different sources of spring forecast uncertainty in runoff loss:
Click to expand...
Dust on snow is affecting runoff in the San Juans too
 
RiverRat68 said:
Yeah, I generally agree with you on this...For a scarce and critical resource, perhaps there should be room for greater control. My post really aims at arguments that say ag uses of CO water should be stopped or curtailed...and ag is the main reason the dams and reservoirs on the CO were built in the first place.
Click to expand...

Ah, gotcha! I agree, this isn't about stopping agriculture any more than it can be about dismantling the dam.

Yeah, I mean there will still be plenty of water for agriculture in general. I think agriculture will almost always still be the primary user. And I think it probably makes economic sense for the agriculture to be the primary user even if inflows continue to go down. It would be hard for other uses to ever get higher than agriculture unless inflows really get catastrophically bad. Right now though, there just aren't good economic incentives for prioritizing that agriculture sensibly (though in some localities that's starting indirectly).

The longer everyone waits to fix the water rights problem is also bad for agriculture - in many cases people need to make long term capital plans based on water rights, regulations and availability (classic case being growing orchards). Regulators waiting until a panic emergency situation before doing something isn't good for agricultural land holders and users much less anyone else!

As someone already mentioned, sadly I expect we won't actually have a realistic long term plan and functional new compact until we get hit with a few bad years in a row that stop power production, impact urban water users, and create significant agricultural economic fallout. Hopefully I'm wrong and that's just old man pessimism kicking in. And I know there are plenty of people working desperately for a plan without the need for a catastrophe. Or maybe hopefully Mother Nature does us a favor and creates just the right amount of drought to force the powers that be to agree to something which is then followed shortly after by some better inflows to restore the system.
 
Outside said:
Dust on snow is affecting runoff in the San Juans too
Click to expand...

Oh, great point. I remember reading about that! Yeah, changing the albedo of the snow pack can really accelerate evaporation. Something anyone who has seen what a pinecone, or even a bark chip, sitting on snow does should be able to relate to. Yet another modeling variable to have to try to integrate! I'm glad forecasting is not my job...
 
You will eat whatever you can afford. Or the government will subsidize. If all the alfalfa farmers sell their water to cities it might be chicken instead of beef.
 
You must log in or register to reply here.
Back
Top