In the green today

Colorado Expat

Well-Known Member
Not by much but its green!
The USGS gauge at the dam indicates the lake level is still dropping. But based on the snow water equivalent plot for the Upper Basin, and hydrographs from various rivers in Colorado, the spring runoff pulse has already started, and about a month early. This should translate into some subsequent rise at Lake Powell, although the cumulative streamflow curves are still tracking record lows west of the Continental Divide. Recall that some of this initial runoff will likely be recaptured by still-dry soils since the Upper Basin remains in drought status, and some of the rest will be retained in Upper Basin reservoirs, which are depleted. By my rough calculations, if we already passed our peak snow water equivalent value around 24 March, then the snowpack will have topped out at 83 percent of long-term average. Inner mountain stations such as Vail and Copper Mountain, after a brief shot of cold weather through tomorrow, are expected to run highs in the 40s and 50s later this week, so the runoff will continue unabated, because the snowpack as a whole has now warmed. In general, an early melt of a sub-par snowpack is not the best scenario, but we will see how it plays out.
 

ndscott50

Active Member
The longer range models are always fun. I looked this morning and the GFS showed a really nice storm next week with lots of moisture.

1649192654376.png
Checked this afternoon and its pretty much gone
1649192734429.png
Hopefully it will trend back the other way as we could really use a few good April storms. Its way to early for the runoff season to begin in the high mountains.
 

scubatim

Well-Known Member
The USGS gauge at the dam indicates the lake level is still dropping. But based on the snow water equivalent plot for the Upper Basin, and hydrographs from various rivers in Colorado, the spring runoff pulse has already started, and about a month early. This should translate into some subsequent rise at Lake Powell, although the cumulative streamflow curves are still tracking record lows west of the Continental Divide. Recall that some of this initial runoff will likely be recaptured by still-dry soils since the Upper Basin remains in drought status, and some of the rest will be retained in Upper Basin reservoirs, which are depleted. By my rough calculations, if we already passed our peak snow water equivalent value around 24 March, then the snowpack will have topped out at 83 percent of long-term average. Inner mountain stations such as Vail and Copper Mountain, after a brief shot of cold weather through tomorrow, are expected to run highs in the 40s and 50s later this week, so the runoff will continue unabated, because the snowpack as a whole has now warmed. In general, an early melt of a sub-par snowpack is not the best scenario, but we will see how it plays out.
Read in the Water news that BOR was starting to reduce outflows in Blue Mesa - I assume Navajo and FG???
 

Colorado Expat

Well-Known Member
The longer range models are always fun. I looked this morning and the GFS showed a really nice storm next week with lots of moisture.

View attachment 17805
Checked this afternoon and its pretty much gone
View attachment 17806
Hopefully it will trend back the other way as we could really use a few good April storms. Its way to early for the runoff season to begin in the high mountains.
The reason we appear to be seeing an early runoff largely relates to air temperature trends. Although there were cold periods this past winter, the overall temperature regime for the past 6 months in western Colorado varied from above normal (top 33 percent of all years of record) to much above normal (top 10 percent of all years of record).

Colorado Surface Temp Anomaly - Oct 2021-Mar 2022.png

Even if more moisture does arrive in April or May, it could fall as rain rather than snow, except at the highest elevations, which would reduce the snowpack even faster.
 

thekid26

Well-Known Member
The USGS gauge at the dam indicates the lake level is still dropping. But based on the snow water equivalent plot for the Upper Basin, and hydrographs from various rivers in Colorado, the spring runoff pulse has already started, and about a month early. This should translate into some subsequent rise at Lake Powell, although the cumulative streamflow curves are still tracking record lows west of the Continental Divide. Recall that some of this initial runoff will likely be recaptured by still-dry soils since the Upper Basin remains in drought status, and some of the rest will be retained in Upper Basin reservoirs, which are depleted. By my rough calculations, if we already passed our peak snow water equivalent value around 24 March, then the snowpack will have topped out at 83 percent of long-term average. Inner mountain stations such as Vail and Copper Mountain, after a brief shot of cold weather through tomorrow, are expected to run highs in the 40s and 50s later this week, so the runoff will continue unabated, because the snowpack as a whole has now warmed. In general, an early melt of a sub-par snowpack is not the best scenario, but we will see how it plays out.
what's your call on how many feet the lake will be up by end of july? i'm not holding you to it, you just seem very level headed and sound very smart on the inner workings of the lake and surroundings. cheers,
 

Todd

Well-Known Member
what's your call on how many feet the lake will be up by end of july? i'm not holding you to it, you just seem very level headed and sound very smart on the inner workings of the lake and surroundings. cheers,
It will be dropping again by the end of July!
 

Colorado Expat

Well-Known Member
what's your call on how many feet the lake will be up by end of july? i'm not holding you to it, you just seem very level headed and sound very smart on the inner workings of the lake and surroundings. cheers,
That is a really tricky question given the number of factors in play here, but I am going to make a WAG that the lake will come up a bit less than the Bureau of Reclamation anticipates, maybe to 2530-2535. But it will not stay there very long, because BOR has been lowballing water deliveries to the Lower Basin states, and that will have to be rectified as we get further into summer.
 

JFRCalifornia

Escalante-Class Member
That is a really tricky question given the number of factors in play here, but I am going to make a WAG that the lake will come up a bit less than the Bureau of Reclamation anticipates, maybe to 2530-2535. But it will not stay there very long, because BOR has been lowballing water deliveries to the Lower Basin states, and that will have to be rectified as we get further into summer.
I agree with that assessment, although I tend to think the peak will be closer to 3540 (since they will still keep releases low in April and May) but I agree that in late summer it will drop more than the normal late summer because BOR has to catch up on releases by Sept 30 to make up for what they have been holding back now and in previous months…
 

Trix

Escalante-Class Member
Even if more moisture does arrive in April or May, it could fall as rain rather than snow, except at the highest elevations, which would reduce the snowpack even faster.
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?
 

Bart

Active Member

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.

 

Trix

Escalante-Class Member
I think either JFR or Drewski found that the annual average date of lowest water is April 6 so it might just be an average year in that respect.
 

POk3s

Well-Known Member
And the next week looks cold too, after a brief warm up. But there is some more precipitation in the forecast at least!
Dorado, how much snow do you figure you got yesterday (4/5)? After spouting off about the couple of inches I looked at the webcams and the charts I could find and it doesn’t look like that to me. Doesn’t matter in the grand scheme of things, just curious.
 

Dorado

Escalante-Class Member
Dorado, how much snow do you figure you got yesterday (4/5)? After spouting off about the couple of inches I looked at the webcams and the charts I could find and it doesn’t look like that to me. Doesn’t matter in the grand scheme of things, just curious.
I was over in Victor Idaho yesterday, but that sounds about right. The webcams looked pretty snowy up around Warren Bridge and the Rim, but it melted pretty fast on the pavement. Probably got more up in the mountains. At least the ground got wet again!
 

JFRCalifornia

Escalante-Class Member
I think either JFR or Drewski found that the annual average date of lowest water is April 6 so it might just be an average year in that respect.
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 on the date 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 keep in mind that in an "average" year, that 30K cfs inflow is sustained for 38 days...

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...
 
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