HomeMy WebLinkAboutSUS443fXJ£00~£ a(;@£~@@ SUSITNA JOINT VENTURE
INTRA-OFFICE MEMOAANOUM
LOCATION Anchorage DATE Decauber 20, 1984 ----
TO L. Gilbertson NUMBER 4.3.1.1
FROM H. Teas
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On 5 December 1984 I travelled to Talkeetna with T. Withrow of ADF&G. On
6 Deceraber a flar~-rate dye study was perfomed in the lower part of
slough 11. On 7 December similar studies were perfomed in sloughs 21
and 10. A sufficient number of measureaents were made to detenaine the
flows in all three sloughs. The flow fromslough 9 was not measured, due
to interference effects of the ice front.
Slough 11
Measurements were made in the lower part of slough 11 (see figure 1). A
Geofilter peristaltic pump was used to inject dye a sufficient distance
above passage reach I (PR-I) to give complete mixing at the base of the
reach. Discrete samples were taken at the base of PR-I and at the Mouth
of the slough. Mixing was complete bela.~ PR-I. Considerable upwelling
and seepage below PR-I was too close to the Mouth to give complete
mixing. The result is a range of flow rates for measurauents at the
mouth. The study was conducted only in the lower slough due to time
constraints involving time of travel of the dye.
Slough 21
The dye injection point in Slough 21 was between PR-II and the fork in
Ehe slough (figure 2). SliDples were taken in PR-II and below PR-I.
SliDples from both sides of the slough at each sampling location showed
canplete mixing of the dye.
Slough 10
The location chosen for dye injection was about 200 feet up the northwest
am from the fork with the •aller northeast ana. Mixing was complete
near the mouth of the slough, but shar~ed some non-uni fona ity at a
sampling site just above the fork in the slough. The range, however'· was
insignificant (leas than 0.1. cfs).
Results
Location Fla.~ Rate
Slough 11 bela.~ PR-I 1.0 cfs
at raouth 1.1 to 1.3
Slough 21 in PR-II 0.4 cfs
below PR-t 2.4 cfs
Slough 10 abo¥1e the mouth of the NE arm 0.8 cfs
at the Mouth of the slough 0.9 cfa
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MAINITEM
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SLOUGH 11
210
I
100
SAMPLNG PC*T •
• ......ECTION POINT '
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• SAMPLING FaNT
A INJECTJON POINT
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SLOUGH 21
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ALAIItA •owtR AUTttOIUI'Y
IUIITMA MYHQILlCTiliC ~C:T
Attachment 3 December, 1984
DYE STUDY PROPOSAL
At present the relationship between mainstem Susitna flows and side
sloughs from groundwater sources is not well defined, especially at very
low flows. Mainatem flow is very low at present, and baa been that way
for several weeks. It is not likely to get any lower in the near future,
and is presently lower than expected from any with-project condi tiona.
Residual stored groundwater is likely to be very low, as there has been
very little input since August from precipitation or presumed lateral
flow from the mainstem. The ice cover has not yet reached the upper
middle reach. We believe that under these conditions the source of side
slough water ilf limited mostly to underlying longitudinal groundwater
flow.
If this study h performed in the iauaediate future, before conditions
change, we can get the des:red slough flow measurements. The data will
be valuable in defining slough flows under worst case conditions for
slough access by salmon. The data will also provide information on the
relationship between the mainstem and side sloughs at very low flows.
These condition• are liable to be altered in the near future due to the.
upstream movement of the ice front, with its' attendant stage increase.
The procedure involved would be to use a fluorometer and fluorescent
tracer dye to measure flow• in side sloughs 11 and 21, and if conditions
permit, in slough 9. The fluorometric technique yields direct flow rate
measurements to ! 2%.
obtain the flow rate:
The technique uses a mass balance equation to
Where C1 • concentration of dye pumped into the slough, c2 •
concentration of dye measured at the slough mouth, F1 • flow rate
(mlJmin) from the pump, and F2 • flow rate (cfs) mesured at the mouth of
421431/12
1
the slough. Dye is injected into the upstream end of the open water in a
slough. Turbulent lixing of ·the dye and upwelled groundwater occurs
downstream of this point. The· concentration of the diluted dye is
measured at the mouth of the slough with the fluorometer. Uniformity of
the mixing at the slough mouth will be checked by making several
measurements across the channel. Dye concentration and flow rate will be
adjusted so that measurements at the slough mouth will be at least ten
times above minimum detectability if slough flows were 10 cfs. Since the
fluoresence of Rhodamine WT is related to temperature, all values will be
noraalized to 20°C using:
WhereC20 • the dye concentration at 20°C, C8 • the dye concentration at
ambient temperature, and Ts • the temperature of the sample.
In order to complete this study before the ice front moves into the area
of concern, it is suggested that the field work be performed during the
first week of December, 1984.
Approximate Budget
2 warm bodies for 2 days
5-6 hr. helicopter time (jet ranger)
transporation to Talkeetna (l/2 day for 2 people)
food and lodging in Talkeetna, 2 people for 2 days
office and lab time:
preparation
analysis
short report
equipment rental
1 man day
1 man day
2 man days
fluorometer, metering puap
dye, batteries, glassware,
sampling pump
421431/12
2
somehwat over $100.00
(ref: Jack Colinell)