Run off starting
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JFRCalifornia
Keeper of San Juan Secrets
Unlikely the Cut is passable until mid- to late June…
RobertGosselin
Well-Known Member
I hate to be a pessimist but the snowpack is rapidly depleting, the river flows are weak, much of the melt is going to the upper reservoirs and the weather is hot and dry. I think we will be lucky to get 30 ft and may only get 20. My comparison to the 2020 snowpack was not very popular a couple of weeks ago but we are significantly behind 2020 now!
I'm pretty much resigned to taking the long way around as I doubt the cut will be open for more than a few days if at all this year.
Very unlikely... but let me cling to my false dreams
nzaugg
Escalante-Class Member
We are dealing with a spring that unfortunately resembles 2020 far too closely.
Inseminator
Well-Known Member
colorado river in rifle CO muddy and rising
A man called horse
Active Member
Likewise the Animas. Snow is disappearing quickly from the San Juans.
Colorado Expat
Well-Known Member
Another aspect of this spring’s quick runoff is linked to the warmer than average temperatures that prevailed over the past winter across the central Rockies. Although it was still cold (it was winter in the mountains, after all), temperatures across western Colorado were still 1-5 degrees F higher than normal, and this in turn means that the snowpack did not get as cold as usual (by contrast, last winter was much colder than average). A recent survey by the private contractor Airborne Snow Observatories indicated that in the upper Roaring Fork Basin near Aspen only 26% of the snowpack had an internal temperature below freezing, with the remainder being at the melting point, or in technical terms "isothermal." These results from the Roaring Fork area also seem to be reflective of much of the snowpack in central Colorado. When snowpack is in this “ripe” condition it only takes a few warm days to trigger rapid melt and runoff. If those days are also windy, then some of the “warm” snow also just sublimates directly into the atmosphere, rather than flowing off the landscape. Windy and unusually warm is exactly the weather that has been prevailing on the Western Slope of Colorado over the past week or so.
In addition, surveys are indicating that the water content in this year’s snowpack is about 12 percent lower than in last year’s. This snow water equivalent is contingent upon what type of snow falls (powder versus heavy wet stuff) and how it gets distributed on the landscape by winds and such. These fine scale snow distribution patterns are not well captured by SNOTEL sites because they are limited in number and at fixed locations, so do not account for drift patterns very well. So the SNOTEL numbers may in fact be too rosy a picture.
At this point we have a mostly isothermal snowpack, with lower SWE than last year, melting quickly under unusually warm conditions for April, with a fair number of windy days thrown in. Based on the SNOTEL data, we have already melted off 17% of this year’s SWE (and as noted above it could be more), inflows are running at 63% of normal, and Lake Powell’s water level has barely budged. So unless something changes soon, it does look like this year’s runoff may come in on the low end of the estimated range. If I was a betting person, I would probably not be putting my money down on a long period of transit through The Cut this year.
In addition, surveys are indicating that the water content in this year’s snowpack is about 12 percent lower than in last year’s. This snow water equivalent is contingent upon what type of snow falls (powder versus heavy wet stuff) and how it gets distributed on the landscape by winds and such. These fine scale snow distribution patterns are not well captured by SNOTEL sites because they are limited in number and at fixed locations, so do not account for drift patterns very well. So the SNOTEL numbers may in fact be too rosy a picture.
At this point we have a mostly isothermal snowpack, with lower SWE than last year, melting quickly under unusually warm conditions for April, with a fair number of windy days thrown in. Based on the SNOTEL data, we have already melted off 17% of this year’s SWE (and as noted above it could be more), inflows are running at 63% of normal, and Lake Powell’s water level has barely budged. So unless something changes soon, it does look like this year’s runoff may come in on the low end of the estimated range. If I was a betting person, I would probably not be putting my money down on a long period of transit through The Cut this year.
JFRCalifornia
Keeper of San Juan Secrets
Yes, it's been a warm (even sometimes hot) spring, dry and windy. And yes, that's caused all the things that @Colorado Expat has very accurately described. But I'm looking at the latest numbers, and I don't think it's time to panic quite yet.
Let me explain why not.
If you recall, USBR's April 24-month study projected a peak at about 3589-90 or so. This was based in part on a CBRFC median projection of 5.7 maf unregulated water supply forecast to Lake Powell from April 1 to July 31. Okay, since then, the Lake Powell's unregulated water supply forecast has been trending downward, and as of today, CBRFC now thinks it's going to be more like 5.15 maf, not 5.7. That's significantly lower, no doubt because of the hot dry weather, but will that actually translate to lower than expected levels at Powell?
To answer that, the first thing you've got to consider is that in its April forecast, USBR was projecting only 5.0 maf would actually flow into Powell from April through July. That is, 5.7 maf would be available, but only 5.0 would get there, presumably because the rest would be impounded upstream, with a small amount lost to evaporation. Now, if instead only 5.1 maf is available, will that mean USBR will decrease the inflow to Powell accordingly? Or will they maintain their targeted 5.0 maf at the expense of the upper reservoirs?
Let's look again at USBR's predicted inflow to Powell for the month of April, which was 645,000 af. Well, as of April 23, with a week still left in the month, about 430,000 af has already entered the lake. To reach the projected 645,000 af by May 1, you'd need an average inflow of about 15,000 cfs for the last week of the month. We're doing about 15,000 cfs right now. It's not going to drop in the next week, and will likely go up, so I suspect we will meet USBR's relatively modest April projection. That is, they weren't predicting a rise this month, which is how most Aprils go. On target.
So at this point, here's what we know. Regulated inflow for April is likely going to be pretty much what USBR projected. Outflow will also match USBR projections. With regard to the upper reservoirs, the Water Database shows that the reservoir levels in Flaming Gorge, Blue Mesa and Navajo have all been relatively flat in the month of April, so inflow = outflow from those reservoirs, more or less, no penalty to Powell. (Details: Navajo has a net gain of about 18,000 af, but Flaming Gorge has a net loss of 13,000 af, and Blue Mesa has lost 8,000 af...so overall, Powell has a very slight net gain from the upper reservoirs). Actually, USBR predicts that regulated inflow to Powell will slightly exceed unregulated--that is, they will release slightly more from the upper reservoirs than they take in. So far, the data supports that is actually happening.
And now here's what we think we know. CBRFC thinks the unregulated inflow to Powell from April 1-July 31 will be 5.1 maf, not 5.7. That means that somehow, somewhere, there will be 0.6 maf less stored in the system than previously thought. And USBR's most recent projection is that 5.0 maf will enter Powell during that time--will they reduce that? Don't know. USBR's projected regulated inflow for May is 1.63 maf, or an average of about 26,000 cfs per day during that month. Solid inflow, but not overwhelming. We will probably see that, or at least come close.
So here's what I take from all of that.
1. Powell's net April-July regulated inflow might be as low as 4.4 maf, or as high as 5.0 maf--that's totally up to USBR, since they regulate the inflow, and the water will likely be available.
2. If it's 5.0 maf, then their April projections are still valid, and the lake will still hit 3589 as predicted, and the Cut would be usable for all of July, and for at least a few days in June and August. If they do this, the upper reservoirs will suffer to the tune of a net loss of 0.6 maf.
3. USBR could instead make it so Powell's regulated inflow is as low as 4.4 maf. If they do, then the upper reservoirs will maintain their status quo, but Powell will suffer. In this case, Powell would peak at only about 3585, and the Cut will barely be open at all.
4. My guess is that USBR does something in between those two scenarios.
5. In any case, with the warm spring, it’s almost certain we’re not coming anywhere near 3600, or even 3595…
So if we're taking a hard look at the latest data, and not just imagining the worst because inflows haven't ramped up yet in all this hot weather, this is what you come up with.
Let me explain why not.
If you recall, USBR's April 24-month study projected a peak at about 3589-90 or so. This was based in part on a CBRFC median projection of 5.7 maf unregulated water supply forecast to Lake Powell from April 1 to July 31. Okay, since then, the Lake Powell's unregulated water supply forecast has been trending downward, and as of today, CBRFC now thinks it's going to be more like 5.15 maf, not 5.7. That's significantly lower, no doubt because of the hot dry weather, but will that actually translate to lower than expected levels at Powell?
To answer that, the first thing you've got to consider is that in its April forecast, USBR was projecting only 5.0 maf would actually flow into Powell from April through July. That is, 5.7 maf would be available, but only 5.0 would get there, presumably because the rest would be impounded upstream, with a small amount lost to evaporation. Now, if instead only 5.1 maf is available, will that mean USBR will decrease the inflow to Powell accordingly? Or will they maintain their targeted 5.0 maf at the expense of the upper reservoirs?
Let's look again at USBR's predicted inflow to Powell for the month of April, which was 645,000 af. Well, as of April 23, with a week still left in the month, about 430,000 af has already entered the lake. To reach the projected 645,000 af by May 1, you'd need an average inflow of about 15,000 cfs for the last week of the month. We're doing about 15,000 cfs right now. It's not going to drop in the next week, and will likely go up, so I suspect we will meet USBR's relatively modest April projection. That is, they weren't predicting a rise this month, which is how most Aprils go. On target.
So at this point, here's what we know. Regulated inflow for April is likely going to be pretty much what USBR projected. Outflow will also match USBR projections. With regard to the upper reservoirs, the Water Database shows that the reservoir levels in Flaming Gorge, Blue Mesa and Navajo have all been relatively flat in the month of April, so inflow = outflow from those reservoirs, more or less, no penalty to Powell. (Details: Navajo has a net gain of about 18,000 af, but Flaming Gorge has a net loss of 13,000 af, and Blue Mesa has lost 8,000 af...so overall, Powell has a very slight net gain from the upper reservoirs). Actually, USBR predicts that regulated inflow to Powell will slightly exceed unregulated--that is, they will release slightly more from the upper reservoirs than they take in. So far, the data supports that is actually happening.
And now here's what we think we know. CBRFC thinks the unregulated inflow to Powell from April 1-July 31 will be 5.1 maf, not 5.7. That means that somehow, somewhere, there will be 0.6 maf less stored in the system than previously thought. And USBR's most recent projection is that 5.0 maf will enter Powell during that time--will they reduce that? Don't know. USBR's projected regulated inflow for May is 1.63 maf, or an average of about 26,000 cfs per day during that month. Solid inflow, but not overwhelming. We will probably see that, or at least come close.
So here's what I take from all of that.
1. Powell's net April-July regulated inflow might be as low as 4.4 maf, or as high as 5.0 maf--that's totally up to USBR, since they regulate the inflow, and the water will likely be available.
2. If it's 5.0 maf, then their April projections are still valid, and the lake will still hit 3589 as predicted, and the Cut would be usable for all of July, and for at least a few days in June and August. If they do this, the upper reservoirs will suffer to the tune of a net loss of 0.6 maf.
3. USBR could instead make it so Powell's regulated inflow is as low as 4.4 maf. If they do, then the upper reservoirs will maintain their status quo, but Powell will suffer. In this case, Powell would peak at only about 3585, and the Cut will barely be open at all.
4. My guess is that USBR does something in between those two scenarios.
5. In any case, with the warm spring, it’s almost certain we’re not coming anywhere near 3600, or even 3595…
So if we're taking a hard look at the latest data, and not just imagining the worst because inflows haven't ramped up yet in all this hot weather, this is what you come up with.
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viking842000
Well-Known Member
Snow pack is great ? I see it MUCH differently... April was a complete bust and the snow pack has deteriorated sadly...
smoke
Well-Known Member
as usual for the details thank you @JFRCalifornia
@viking842000 as far as snow pack I read in different report that the Colorado snow pack was above the average of the past 20 years. Not as much as last year but still above. Here is one of the report Colorado show above average at 109%
colorado
and Utah show also above average
utah
wyoming snow pack is below average but it does not contribute a lot to Lake Powell
@viking842000 as far as snow pack I read in different report that the Colorado snow pack was above the average of the past 20 years. Not as much as last year but still above. Here is one of the report Colorado show above average at 109%
colorado
and Utah show also above average
utah
wyoming snow pack is below average but it does not contribute a lot to Lake Powell
Dorado
Keeper of San Juan Secrets
The headwaters of the Green in Wyoming contribute a significant amount to the Colorado. And the average snowpack for the entire basin is now sitting near the 20 year average, which is a pretty crappy average to compare to!!!
viking842000
Well-Known Member
That report is from April 4… here is today’s reporting after an incredibly dry and windy remainder of April. Now 88% unfortunately as our snow is evaporating quickly
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Paul_G
Well-Known Member
Any of this going to fall on the Powell side of the Rockies?
denvergazette.com
30 inches of snow incoming on multi-day storm: Whiteout daily snow report, April 25
Snow showers, then heavier snow showers, then SNOW, before less snow to end the last weekend of April at Colorado's remaining open ski areas and resorts.
denvergazette.com