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huckin harms
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Topic: Sky gauge Posted: 02 Dec 2014 at 9:26am |
Just a heads up... due to all the rains, and subsequent high water, the gauge is now significantly off. At present the reading suggest 8k, but it is much closer to 4k.
Edited by huckin harms - 13 Jan 2015 at 7:14pm
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Nick
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Posted: 02 Dec 2014 at 9:43am |
Thanks for the beta harms. Anyone able to get out there today?
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Slackkinhard
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Posted: 09 Dec 2014 at 1:03pm |
What's the scoop on the SKY gauge these days? Is it accurate?
Edited by Slackkinhard - 09 Dec 2014 at 1:04pm
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Sam_Graftton
Splat Wheeler
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Posted: 09 Dec 2014 at 3:04pm |
I did a lap yesterday it was reading 6k I thought it was close 4,500
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Nick
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Posted: 09 Dec 2014 at 3:45pm |
Ran it today and seemed to be at least 1500 off. This last weekend seemed like 2000... Safe to say its between 2000-1500cfs lower than what's predicted. Beware for when it's accurate!
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Slackkinhard
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Posted: 09 Dec 2014 at 3:46pm |
thanks guys, info much appreciated
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jP
Rio Banditos
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Posted: 10 Dec 2014 at 2:17pm |
Yup. Guage is still wacky. Brett, Nick and I just ran it and the guage reading I got from the 41411 text service was 11,000ish, yet on the water we agreed it felt more like 8,000+. Our theory is that the gravel bars down near Goldbar where the guage is has been shifted by the 60k blast. So maybe the cross section they take reading from doesn't match the shape, or is filled in w/ gravel deposits making it read high?
On another important note:
As of today, wed dec 10th
There is a 40' long spanning log across most of the entire channel on the North Fork Sky. It is located near the bottem of the second to last rapid before the confluence.
Here is its exact location, in greater detail...
So you just paddled past Sportsman's, the squatter camp on R. Right below Llama ledges. You paddle through the flatwater past the islands on R. Left. As you approach this next rapid, under the powerlines, the river bends left. Tons of wood collects on R. Right where a huge hole lurks at highwater.This channel spanning wood is at the very top of the gravel bar as the river aims back toward its left bank. It could be two pieces, couldn't tell. At about 8,000cfs we snuck around it on R. Right, but far R. Left would work too.
The important thing is that you know its there as you approach the rapid because a lot of water concealed it at 8k. Likely if the river comes up much at all it should flush, just look out for novices that tag along with you and make sure they have a stragey of avoidence before they enter the rapid.
Stay safe out there and use your intellect, keep that rabid dog on a leash.
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Slackkinhard
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Posted: 11 Dec 2014 at 2:19pm |
Seems really strange....it's been raining hard for nearly 20hrs here in the Everett area, but the Sky gauge is showing it dropping
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jP
Rio Banditos
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Posted: 11 Dec 2014 at 3:23pm |
Well, I actually believe the trend as indicated by the graph. Up here in Index the rain has been sporadic this week w/ some surprisingly dry patches mixed in.
The graph at the time of this post shows that it has adjusted to reflect the last rounds of rainfall, kind of a "King's Crown" shape to the hydrograph.
The issue with the guage however, seems more reflective of gravel and sand deposition where the cross section of the guage is near Gbar. Hence it reading 2000 or so more cfs than it actually is. Seems like USGS needs to recalibrate the actual cross section of the guage to reflect the new shape of the river bed that presumably doesn't match the old one.
Anyone ever contact these people or know who to email? I don't have much internet access these days to hunt n peck for such info.
Often I feel as though people are too quick to claim the guage is "off". It amounts to a "boy who cried wolf" syndrom and often I wanna call bullsh*t when I hear these claims. I am pretty observant of the river environment when I'm out there, so if I don't notice a change I tend to be skeptical of these claims. Doesn't mean they are always invalid, but they usually are. Some people pretend to know more than they do, others sincerely believe they are more tuned in than they are. As far as my own observations I tend to try to be objective and honest with myself.
In this case, it is a very dramatic discrepency and several of us have been out here several times a week and all of are observations consistently match up. This is added to the credibility of paddlers who have known the Sky for a decade or longer- Harms, Brett, Darren, ect.
I suppose that if it was only and error of a few hundered CFS or less, it would be a blurry issue but it seems to be 1500-2500 off, or proportionately equivilent.
We all roughly guessed it to be 7800ish today. I admit that despite my increasing familiarity with the Sky, these guessing games are tough to play. There are several spots on the river I use to correlate the flow, but the best one is Boulder Drop, since it is by far the rapid most of us spend the most time observing.
Where it gets fuzzy for me lies in the fact that lately I am all about taking alternate lines in B.D. , and I try to mix n match them. I figure I got all spring and summer to run the raft lines. Consequently placing my lines in alternative places, it can be hard to keep track of these guage points. Its made for a fun game this week.
Anyway, yes it is WAY OFF. But for those who are on the fence, I wouldn't let the ambiguity deter you from coming out. You can still scout BD and/or take conservative lines. It is a great run.
BTW- that huge spanning piece of wood is still in the 2nd to last rapid on the Nfrk Sky, upstream of the confluence. Watch out and communicate this to paddlers at the put in
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itchy
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Posted: 12 Dec 2014 at 12:20am |
I emailed a contact at the Survey to let them know.
As far as how these sorts of errors go, just in case anyone cares, the gauges measure a vertical, linear scale called the stage (measured in feet here in the land of freedom), and then convert the stage to streamflow (volume or feet^3 per second) mathematically, with some variables that are calibrated to the site itself based on measurements of the river channel and velocity at various stages.
Streamflow doesn't scale linearly with river stage, as I'm sure almost everyone here knows. It varies more like:
streamflow = stage^n,
where n is some number greater than one (for the Sky, I think it's around 4.2 for moderate flows, if I squint at the hydrograph just right). In reality there can be a couple more variables used in the calibrations that JP mentioned but nothing of major consequence--it's that power law that has all the power. (Also note that these numbers won't necessarily hold at very low or very high flows.)
The point of this is that the errors in the gauge will probably scale nonlinearly w/ the level, so a reading of 6000 CFS may be 800 CFS high, but a reading of 11000 CFS may be 2500 off.
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Slackkinhard
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Posted: 19 Dec 2014 at 9:43am |
Sky gauge bigtime bonkers again
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mikefromTX
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Posted: 21 Dec 2014 at 9:12am |
I think they fixed the guage. It had a big red star on the graph representing "measured flow". It went from around 5k to 3k almost instantly(we ran Friday and the reading was 4,800 and we thought it felt around 3ish). I don't want to say for sure it's fixed, so can someone who's run it since Friday confirm?
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huckin harms
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Posted: 13 Jan 2015 at 7:13pm |
For what it's worth, several have commented on noticing the gauge being off AGAIN! Today I noticed water still cresting over a rock in the drop that is indicative of 4k. Comments have guessed the reading is off by several hundred to maybe 500 cfs or so. Of course this is all subjective but as flows increase so does the discrepancy. Anyways, Neds seemed more sticky than usual so maybe this explains it, or maybe Ned is just more crotchety.
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Blair
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Posted: 14 Jan 2015 at 5:21pm |
It's defintely off. I ran it yesterday and that was no 3,500. Neds was real sticky icky for sure.
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dave
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Posted: 14 Jan 2015 at 8:28pm |
I havnt run the Sky in a long time, and I think it is off too...
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Nomad
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Slackkinhard
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Posted: 14 Jan 2015 at 10:00pm |
Does that mean it is higher or lower than it displays?
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Blair
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Posted: 14 Jan 2015 at 10:19pm |
It is higher than it displays.
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Slackkinhard
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Posted: 14 Jan 2015 at 10:40pm |
seems to be dropping. I was hoping to ditch work for a few hours and get a run in, but I'm pretty new and am not sure what to expect
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