Snowpack

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Dorado said:
High pressure sitting over the Southwest is forecast to break down by the middle of next week 🤞 That high pressure dome keeps forming, it has been there pretty much continuously since July!!!

JFR, I would be interested to know what those big drops and gains are in terms of acre-feet? Dropping a bunch when the lake is mostly full really highlights how bad some of those drought years were....
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Here's the volume and change in these years, all based on the Sept 30 reading each year (end of water year)

  • 2001: 3664 (-13 feet) 19.1 maf total volume (-1.8 maf from previous Sept 30)
  • 2002: 3626 (-38 feet) 14.5 maf (-4.7 maf from previous year)
  • 2003: 3603 (-23 feet) 12.1 maf (-2.4 maf)
  • 2004: 3570 (-23 feet) 9.2 maf (-2.9 maf)
  • 2005: 3602 (+32 feet) 11.9 maf (+2.7 maf)

  • 2006: 3602 (no change) 11.9 maf (-0.02 maf)
  • 2007: 3602 (no change) 11.9 maf (+0.01 maf)
  • 2008: 3627 (+25 feet) 14.5 maf (+2.6 maf)
  • 2009: 3635 (+8 feet) 15.5 maf (+1.0 maf)
  • 2010: 3634 (-1 foot) 15.3 maf (-0.2 maf)

  • 2011: 3653 (+19 feet) 17.6 maf (+2.3 maf)
  • 2012: 3621 (-32 feet) 13.9 maf (-3.7 maf)
  • 2013: 3591 (-30 feet) 10.9 maf (-3.0 maf)
  • 2014: 3605 (+14 feet) 12.3 maf (+1.4 maf)
  • 2015: 3606 (+1 foot) 12.3 maf (+0.05 maf)

  • 2016: 3611 (+5 feet) 12.8 maf (+0.5 maf)
  • 2017: 3628 (+17 feet) 14.6 maf (+1.8 maf)
  • 2018: 3592 (-36 feet) 11.0 maf (-3.6 maf)
  • 2019: 3615 (+23 feet) 13.3 maf (+2.2 maf)
  • 2020: 3596 (-19 feet) 11.4 maf (-1.9 maf)
A couple of things stand out here. The first is that if you look on the bright side, the period 2005-17 was either upward trending in terms of lake volume or broke even every single year but two. And we are still ahead of what the lake was experiencing at the end of Sept 2004.

But on the downside, those two years (2012-13) in the middle of that long rise from 2005-17 erased a lot of the gain made in the other 10 years. The net increase in volume after those years (2004-17) was 5.4 maf--58 feet of rise. But those two years in the middle were killers--dropping 6.7 maf.

And the four years from 2000-04 saw a 9.9 maf drop!! So yes, a prolonged drought is serious with regard to lake levels and volume. Recovery is much slower than the drop on a year to year basis.
 
JFR, so 4.2million acre feet to drop down to 3490. Interesting to note that is slightly less than half the Colorado Compact allotment the Upper Basin states are supposed to send down to Lake Mead and the Lower Basin. And I do believe that around half the lake volume is over 3615. What I find interesting here is that someday something is going to have to give. When the compact was signed into water law the powers that be were presuming an extremely generous average flow of 16.5 million acre feet in the Colorado basin.
 
jayfromtexas said:
JFR, so 4.2million acre feet to drop down to 3490. Interesting to note that is slightly less than half the Colorado Compact allotment the Upper Basin states are supposed to send down to Lake Mead and the Lower Basin. And I do believe that around half the lake volume is over 3615. What I find interesting here is that someday something is going to have to give. When the compact was signed into water law the powers that be were presuming an extremely generous average flow of 16.5 million acre feet in the Colorado basin.
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Yep. And just to clarify, the volume at 3490 is 4.2 maf, so the would take a drop of 5.8 maf from today to get there. And full pool now is about 24.3 maf (it used to be higher, but siltation has eaten into the capacity), so the lake is half full at about 12.2 maf, which is at about 3605.
 
... and inflow rarely if ever comes anywhere near the 16.5 maf needed to satisfy all water rights under the Compact. According to USBR, the average from 1981-2010 was 10.83. Only five years since 1963 have exceeded 16.5 maf inflow, and that would be 1983-86, then 1997. Thats it.
 
JFRCalifornia said:
... and inflow rarely if ever comes anywhere near the 16.5 maf needed to satisfy all water rights under the Compact. According to USBR, the average from 1981-2010 was 10.83. Only five years since 1963 have exceeded 16.5 maf inflow, and that would be 1983-86, then 1997. Thats it.
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JFR, indeed. Seems foolish that the compact won't or can't be amended. Legend has it that the powers that be used an extraordinarily wet period to base the apportionment of Colorado River off of.

So I looked up some elevations on Powell and pretending the silt doesn't bury the historic river channel for great distance into the reservoir I found the following.
Elev RM Nearby River Feature/Canyon Remarks
3700 201.5 Rapid 25 Normal pool elevation (haha)
3621 196.7 Rapid 33/Gypsum Canyon Current extent of exposed historic channel (mostly mud canal below here)
3600 195.5 Rapid 37/Palmer Canyon Half the volume of FP Powell is above this elevation (approx.)
3490 182.7 Dark Canyon/Rapid Minimum power pool elevation of Lake Powell
3460 169.5 N Wash/Dirty Devil Takeout Perched river channel deviates to the northwest of historic channel
3370 130.0 Hansen Creek Dead pool elevation at Glen Canyon Dam

Have you seen the Returning Rapids Project website?
 
jayfromtexas said:
JFR, indeed. Seems foolish that the compact won't or can't be amended. Legend has it that the powers that be used an extraordinarily wet period to base the apportionment of Colorado River off of.

So I looked up some elevations on Powell and pretending the silt doesn't bury the historic river channel for great distance into the reservoir I found the following.
Elev RM Nearby River Feature/Canyon Remarks
3700 201.5 Rapid 25 Normal pool elevation (haha)
3621 196.7 Rapid 33/Gypsum Canyon Current extent of exposed historic channel (mostly mud canal below here)
3600 195.5 Rapid 37/Palmer Canyon Half the volume of FP Powell is above this elevation (approx.)
3490 182.7 Dark Canyon/Rapid Minimum power pool elevation of Lake Powell
3460 169.5 N Wash/Dirty Devil Takeout Perched river channel deviates to the northwest of historic channel
3370 130.0 Hansen Creek Dead pool elevation at Glen Canyon Dam

Have you seen the Returning Rapids Project website?
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Great stuff. Yes, the late 1910s and early 1920s were a pretty wet period in the SW, and so it's true they overoptimistically based their assumptions about Colorado River flow on unrealistically high numbers. It's one reason everyone now assumes we're seemingly always in perpetual drought--more accurately, something like 11 maf is, and has been, "normal" for a long time and 15-16 maf is anomalously high. And on that decidedly unscientific basis, the future of western water was launched almost a hundred years ago.

I hadn't seen the Returning Rapids Project site until you pointed it out--pretty interesting. I'll have to dig into that a bit more.

As for those elevations and locations, where did you find those? Also interesting. The 3700 location (just below Rapid 25) is indeed the historic theoretical high water mark for Powell. In terms of Lake Powell mile markers, that would be MM172, or about 33 miles above Hite! As for all the other figures down to North Wash, that's all quite a testament to the powers of siltation. Today, we see mudflats all around Hite and the river extends sometimes even down toward White Canyon at 3600. But consider that the Hite auto ferry operated on the river until June 5, 1964, at which point it went down for good because of rising waters from the lake.... which on that date was only at 3443! So there's some pretty deep silt up in that part of the lake...
 
JFR, I hope someone will be able to get down there at the low point and check out where the delta front is this year. From what I've seen it's right around between Trachyte and White Canyon. As for sources I've found some great information and old maps here: On The Colorado - Resources. Not a very scientific citation, sorry bit rusty. But yes it bewilders me about all this talk of drought and as yes it looks like 11maf is more likely a normal flow value for the Colorado. The southwest is headed for a water disaster here sooner or later.
 
a lower lake levels mean less evaporation losses... a meme for the '20s.

yet in the end i just hope for some real humdingers of storms to get the ground soaked again good a few times and then plenty of snow on top of that to keep it all from evaporating followed by a very very long wet cool spring.

am i asking for much here? proabably. but a water nerd can dream can't he? :) peace to all, hope this weather pattern changes soon.
 
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