# Main Salmon flow questions



## David L (Feb 13, 2004)

I've got friends going down the Main Salmon from Corn Creek to Carey Creek in a few weeks. On the Idaho Streamflow page (USGS Current Conditions for Idaho_ Streamflow) I don't clearly see what this flow is.

Is the reading for Salmon River at Whitebird (now 42,200 cfs) close enough by itself? (I can't see from the monitor location map where this is relative to Corn Creek). Or, do I need to add in the MF Salmon River at Mouth (10,100)? Plus other rivers feeding in to the Main?

There would be youngsters on the trip. Near 52,000 is a high flow. For the Main what is considered moderate, high, and extreme?

Also, what might be the history of this flow dropping over the next few weeks?

Lastly, I've looked at the Snotel information. Any good guesses out there of where this flow will be in a few weeks?

Thanks much for your help, I know it's a lot of questions. Appreciate it.

david


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## BenSlaughter (Jun 16, 2017)

Add the MF @ the mouth + The Salmon @ Shoup + maybe 5% for some buffer to get the gauge at Corn.
I've run it at 6+ a few times. I'm not sure I'd want kids along. When it drops down around 4' it's more manageable.


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## wdeutsch (Apr 27, 2020)

For me, it's not so much the difficulty of the rapids at higher flows, it's the consequences of a swim (especially for youngsters). I can't speak to _really_ high flows, but we did it 2 years ago at a touch over 5' on the ramp. It was fast and pushy - not like a MFS, but also not the casual pool-drop affair that the main has a reputation for. At that level, swims could be long and VERY cold. Getting on the wrong side of Chittam looked like a way to have a REALLY bad day. For my personal safety/peace-of-mind, I'd put that level in the "drysuit required" category of flow. 

Ben is spot on with how to get the approximate reading at the ramp from the gauges. I'm crossing all my fingers and toes for a fast drop-off in flows, since I launch in a week and a half, but I'm not optimistic. My cutoff will bea combined 17K on the two gauges, since we have some less experienced folks along and I don't need the stress of managing that for 6 days at high flows.


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## BenSlaughter (Jun 16, 2017)

I'll wager we see a second spike in flows, before things start to drop. My crystal ball is down for repairs, so I can't predict when.
But I think when it warms back up, you'll see the flows at Corn back over 6' -sometime in the next 2 weeks. Then it will start to taper down to summer flows.

It's been a weeeeiiirrd spring!


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## David L (Feb 13, 2004)

Thanks Ben and W. I completely missed the flow data at the Salmon at Shoup. That plus the MF flow would have answered my first question very easily. Weird how you can miss things right in front of you, except the big hole in the river!


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## king kong kev (Aug 31, 2006)

Here is a website which does the math for you:





MAIN SALMON FLOW - ThingSpeak IoT


This flow is computed by adding the values for "13307000 SALMON RIVER NR SHOUP ID" and "13310199 MF SALMON RIVER AT MOUTH NR SHOUP, ID". Level @ Corn Creek ramp is approximate. Use at your own risk, no warranties implied! - MAIN SALMON FLOW on ThingSpeak - ThingSpeak is the open IoT platform...




thingspeak.com





It lists the sum of the MF at Mouth gage plus the Main Salmon at Shoup as well as the stage at the ramp.


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## tpalka (Oct 31, 2003)

king kong kev said:


> MAIN SALMON FLOW - ThingSpeak IoT
> 
> 
> This flow is computed by adding the values for "13307000 SALMON RIVER NR SHOUP ID" and "13310199 MF SALMON RIVER AT MOUTH NR SHOUP, ID". Level @ Corn Creek ramp is approximate. Use at your own risk, no warranties implied! - MAIN SALMON FLOW on ThingSpeak - ThingSpeak is the open IoT platform...
> ...


I'm happy to see someone is still using it -- wasn't sure if I should discontinue it  

Tom.


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## denali1322 (Jun 3, 2013)

tpalka said:


> I'm happy to see someone is still using it -- wasn't sure if I should discontinue it
> 
> Tom.


Thanks for sharing this. I was following the math and gauges, but this gave me confirmation that my 17k calc was right.


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## idahogiants (Aug 19, 2020)

tpalka said:


> I'm happy to see someone is still using it -- wasn't sure if I should discontinue it
> 
> Tom.


I've been looking at all sorts of different Main flow resources over the years and this one is tip top for current information at the correct gauge locations. 

Thanks for building this gem


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## idahogiants (Aug 19, 2020)

> I'm crossing all my fingers and toes for a fast drop-off in flows, since I launch in a week and a half, but I'm not optimistic. My cutoff will be a combined 17K on the two gauges, since we have some less experienced folks along and I don't need the stress of managing that for 6 days at high flows.


FWIW, I have been watching flows, weather and snowpack like a hawk for a potential 7/10 launch. With cooler weather and storms up until 6/7 and then 80 degree days and sun I would wager it will be over or near 26k late next week based on historical bumps. As of this morning, it is at 21k and rising. Yeeks.


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## David L (Feb 13, 2004)

Interesting conversation, thanks everyone. What might be the flow speed when it's in the upper teens, near 20k? That's a big potential problem, how fast a swimmer would be moving.


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## BenSlaughter (Jun 16, 2017)

It's variable, of course, but to give you an idea, a couple years ago we did 48 miles the first day without trying too hard. Flow was a bit higher, around 22k.


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## dgketchum (7 mo ago)

Edit: I made the mistake of adding the MF Salmon at MF Lodge, instead of MF Salmon at Shoup. Corrected below:

I added the hydrographs from MF Salmon and Shoup gages to estimate flows at Corn Creek, for complete years since the Shoup gage went online in 2002 through 2020. Peak median flow is 14,820 (under 5 ft) on June 4th, but this year is different. Perhaps a nearly analogous year is 2011, with its late snows. We don't have quite the snowpack we did in 2011, but we're close at certain SNOTEL sites in the headwaters (Mill Creek Summit SNOTEL), and less so at others (Banner Summit SNOTEL). For reference, in 2011 the river didn't peak until June 24 at 27,000 cfs (over 7 ft). Obviously, the high flows on the Salmon are very sensitive to snowmelt rates, and there's a lot of snow still up there, and we don't know how fast it will melt.

Looking at my Corn Creek flows vs. Whitebird flows in late June over the years, Corn Creek is about 50-58% of what is measured at Whitebird. I don't know anything about the NOAA river forecast model, but they do provide a 7-day flow forecast and a weekly exceedance probability product for the whole summer. I'd take their flow forecast and multiply it by 0.55 to forecast Corn Creek flow.

Given the snowpack, next week's warm forecast temperatures, and the rain; I predict Corn Creek will peak on the 13th at 25k, and come down to 12k for my launch June 22nd.

Note: We are two rafts on our June 22nd launch. If it's hairy and another group wants to team up for safety, hit me up.

Predicting hydrographs is a cool problem.


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