Snake River below Swan Falls (Ramp gage) Snake River near Murphy Carl Rundberg Pete Vidmar
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- Slide 1
- Snake River below Swan Falls (Ramp gage) Snake River near
Murphy Carl Rundberg Pete Vidmar
- Slide 2
- Gage Locations Swan Falls Dam Snake Riv blw Swan Falls Snake
River near Murphy
- Slide 3
- Rating curve development Snake River below Swan Falls Rating
curve development Calibrated with142 measurements Measurements made
during steady state conditions to remove travel time Measurements
over wide range of time 1995 to 2013 Range in flows from 4,370 cfs
to 40,300 cfs
- Slide 4
- Control features Snake River near Murphy: Rock riffle ~300yds
downstream of gage. Riffle no longer controls when aquatic growth
is in channel. Aquatic vegetation grows rapidly during warm season
with low flows Snake River below Swan Falls: Rock riffle control
regardless of season
- Slide 5
- Snake River near Murphy: Rating curve Shifting
- Slide 6
- Snake River near Murphy Rating zoomed: seasonal trends Shifting
up to ~1 ft due to aquatic vegetation
- Slide 7
- Snake River below Swan Falls Rating
- Slide 8
- Snake River below Swan Falls Rating Zoomed: small random
scatter
- Slide 9
- Murphy discharge up to 31% from rating Ramp discharge only 6%
from rating
- Slide 10
- % change in flow due to shifts
- Slide 11
- Shifts in feet over time
- Slide 12
- % difference
- Slide 13
- Summary Snake River near Murphy Aquatic growth causes shifting
Shifts > 0.90 ft % difference from rating > 30% Change in
flow between measurements can be as much as + -15% Snake River
below Swan Falls No apparent aquatic growth Shifts scatter up to
0.3ft (likely due to gage calibration) % difference from rating
< 6% Change in flow between measurements generally+ - 5% Some of
these inaccuracies are due to different standard of calibration and
less precise measuring equipment at the gage.
- Slide 14
- Potential Velocity Index Site Swan Falls Dam Snake Riv blw Swan
Falls Snake River near Murphy Potential Velocity Index Site
- Slide 15
- Potential Velocity Index Site
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- Slide 17
- Slide 18
- Snake River below CJ Strike
- Slide 19
- Site specific conditions on the Snake River below CJ Strike
Interference from aquatic vegetation Aeration caused by: spillway
vacuum breaker operations at the power plant
- Slide 20
- Possible alternatives to the current gage Reverting back to a
stage-discharge rating Moving the gage location downstream
Utilizing the Winter-Kennedy turbine flow meters Some combination
of these options