In the green today
- Thread starter Yos
- Start date
Colorado Expat
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.
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.
Checked this afternoon and its pretty much gone
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.
Checked this afternoon and its pretty much gone
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.
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 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).
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.
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
It will be dropping again by the end of July!
Colorado Expat
Well-Known 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.
JFRCalifornia
Escalante-Class Member
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
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.
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...
Piece-O-Crappie
Active Member
Aaaaaaaannnndddd back into the red
Dorado
Escalante-Class Member
And the next week looks cold too, after a brief warm up. But there is some more precipitation in the forecast at least!
POk3s
Well-Known 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.
Dorado
Escalante-Class Member
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
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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