Lake Level Projections... June 2019 best guess
- Thread starter JFRCalifornia
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JFRCalifornia
Keeper of San Juan Secrets
Here’s an update on how it seems we’re tracking for where the lake will top out at. On June 8, the lake finally exceeded an inflow of 50,000 cfs for the first time this year, after being at 30K+ since May 19. This pattern correlates very closely to 1995, when inflow topped 30K+ on May 16, and 50K+ on June 5. In 1995, peak inflow exceeded 96K cfs, which it hit on June 21—and it maintained 50K+ cfs through July 24.
But here’s the really interesting thing—according to the NRCS, the remaining snowpack in the Upper Colorado and San Juan basins as of June 1 this year is off the charts, almost literally. As a percentage of median (and granted, median of June 1 is a lot less than say April 1), we were at over 400% on each as of June 1 (compared to 230-240% in 1995--see attachments), and way higher than that as of June 9 (according to BOR), as temperatures have just started rising enough to begin the serious snowmelt. So there’s a lot more potential than we had in 1995—in fact, any year back to 1986, the first one which NRCS graphs the June 1 data for the Upper Colorado and San Juan.
And what about the comparative outflow? This year, we’ve had a remarkably steady pattern—a daily release of about 11-12K cfs, which is likely to continue based on BOR projections. In 1995, daily releases in June and July were much higher, more like 15-17K cfs, which is a huge difference. That means this year we are keeping about 10,000 acre feet more in the lake each day compared to 1995. Over a 3-month period, that’s roughly 1.0 MAF. In 1995, they released a lot because the lake was already at 3645 in March of that year, and they wanted to avoid an uncontrolled rise as in 1983. Those relatively big releases suppressed the net volume increase that year. And yet even with that, the lake increased in volume by 6.78 MAF that summer, and rose 49 feet, to 3694—nearly full.
So what does this mean for 2019? Well, if there is greater net inflow through the end of June and July than in 1995 (likely, given what’s left of the snowpack), and there is less water released than in that year (also likely, given the projected release pattern compared to 1995), we’re going to end up with a greater net volume increase than in 1995. How much is hard to tell. But we ended up with a net increase of 6.78 MAF that year. In 2019, if we end up with a net gain of, say 7.5 MAF, we’d be at 16.5 MAF in total lake volume… or a lake level of about 3645, a rise of 77 feet!!
Is that even possible? Well, the data tells me yes—sure it is. But lots of things could work against that, such as if the Bureau decides to release a lot more in this big year to help Mead. That would pull down the rise. Or if the snow melts too quickly, which would contribute to higher evaporation and possibly induce the Bureau to release more water. Or if the data is wrong--or incomplete. Or if I’m reading it wrong.
The one thing that is a little different about 1995 is they had a steadier (more normal) early spring snowmelt pattern. So by June 9, the lake volume had already risen 2.3 MAF since early April. This year, that early season rise has only been 1.8 MAF (very little melted so far)... so we’ll see how much “catch up” happens as temperatures spike... still, it’s in the same ballpark...
But to me, it’s just starting to look even more like 3630+…
But here’s the really interesting thing—according to the NRCS, the remaining snowpack in the Upper Colorado and San Juan basins as of June 1 this year is off the charts, almost literally. As a percentage of median (and granted, median of June 1 is a lot less than say April 1), we were at over 400% on each as of June 1 (compared to 230-240% in 1995--see attachments), and way higher than that as of June 9 (according to BOR), as temperatures have just started rising enough to begin the serious snowmelt. So there’s a lot more potential than we had in 1995—in fact, any year back to 1986, the first one which NRCS graphs the June 1 data for the Upper Colorado and San Juan.
And what about the comparative outflow? This year, we’ve had a remarkably steady pattern—a daily release of about 11-12K cfs, which is likely to continue based on BOR projections. In 1995, daily releases in June and July were much higher, more like 15-17K cfs, which is a huge difference. That means this year we are keeping about 10,000 acre feet more in the lake each day compared to 1995. Over a 3-month period, that’s roughly 1.0 MAF. In 1995, they released a lot because the lake was already at 3645 in March of that year, and they wanted to avoid an uncontrolled rise as in 1983. Those relatively big releases suppressed the net volume increase that year. And yet even with that, the lake increased in volume by 6.78 MAF that summer, and rose 49 feet, to 3694—nearly full.
So what does this mean for 2019? Well, if there is greater net inflow through the end of June and July than in 1995 (likely, given what’s left of the snowpack), and there is less water released than in that year (also likely, given the projected release pattern compared to 1995), we’re going to end up with a greater net volume increase than in 1995. How much is hard to tell. But we ended up with a net increase of 6.78 MAF that year. In 2019, if we end up with a net gain of, say 7.5 MAF, we’d be at 16.5 MAF in total lake volume… or a lake level of about 3645, a rise of 77 feet!!
Is that even possible? Well, the data tells me yes—sure it is. But lots of things could work against that, such as if the Bureau decides to release a lot more in this big year to help Mead. That would pull down the rise. Or if the snow melts too quickly, which would contribute to higher evaporation and possibly induce the Bureau to release more water. Or if the data is wrong--or incomplete. Or if I’m reading it wrong.
The one thing that is a little different about 1995 is they had a steadier (more normal) early spring snowmelt pattern. So by June 9, the lake volume had already risen 2.3 MAF since early April. This year, that early season rise has only been 1.8 MAF (very little melted so far)... so we’ll see how much “catch up” happens as temperatures spike... still, it’s in the same ballpark...
But to me, it’s just starting to look even more like 3630+…
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JFRCalifornia
Keeper of San Juan Secrets
Yep...
JFRCalifornia
Keeper of San Juan Secrets
Looks like it’s really ramping up today... 64k cfs on June 9, a 1.09-foot rise!! That means the lake added 0.1 MAF in one day. Put that in perspective—that’s the same as almost 10% of the remaining capacity of all the reservoirs combined above Powell... a lot of water...
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Trix
Keeper of San Juan Secrets
And about 74000 at 1600 today!
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