Comparison of Tracer-Dilution and Current-Meter Measurements in a Small Gravel-Bed Stream, Little Lost Man Creek, California Gary W.
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Transcript Comparison of Tracer-Dilution and Current-Meter Measurements in a Small Gravel-Bed Stream, Little Lost Man Creek, California Gary W.
Comparison of Tracer-Dilution and
Current-Meter Measurements
in a Small Gravel-Bed Stream,
Little Lost Man Creek, California
Gary W. Zellweger, Ronald J. Avanzino, and Kenneth E. Bencala
(1989)
Purpose of Study
Present and compare discharge
measurements taken by two different
methods:
◦ Tracer-dilution
◦ Current-meter
Suggest how much discharge is flowing
through the channel gravel
Background
Current-meter technique preferred
method to determine discharge
Issues with current-meter method:
◦ Shallow depths
◦ Flow through gravel
o
o
Rough bottom
Discharge variation
Continuous tracer-dilution methods can
accommodate these factors
Tracer-Dilution Method
Can be used to calculate discharge at
multiple sites
Requirements:
◦ Tracer thoroughly mixed with stream
◦ Conservative tracer
Tracer-Dilution
Method
…Plateau Concentration
Can be used to calculate discharge at
multiple sites
Requirements:
◦ Tracer thoroughly mixed with stream
Tracer injection.
◦ Conservative
tracer
Concentration
rises to…
Tracer-Dilution Method
Can be used to calculate discharge at
multiple sites
Requirements:
◦ Tracer thoroughly mixed with stream
◦ Conservative tracer
Tracer-Dilution Method
Stream discharge below injection point:
Qb = Qi (Ci –Ca)
(Cb – Ca)
Qb = Stream discharge below the injection point
Qi = Injectant discharge
Ci = Tracer concentration in injectant
Ca = Tracer concentration in stream above injection point
Cb = Tracer concentration in stream below injection point
Site Description
Little Lost Man Creek, CA
Coastal 3rd order stream
◦ 10 km length, N-NW flow
◦ Late summer flows 6 L/s
◦ Winter high flows 5,700 L/s
Study reach = 330 m
◦ Poorly sorted, sand-boulder
◦ Gravel sediments > 1 m thick
Tracer-Dilution Method
Cl-Li pumped into stream continuously (8d)
◦ Chloride concentration = 170.1 g/L
◦ Daily injection rate = 37.29±.32 mL/min
◦ Mixing length = 300m
Secondary injection on 7thday
◦ Na, Cl, rhodamine WT (24 h)
◦ Mixing length = 25m
Sampled hourly with automatic samplers
◦ 300m above
◦ 330m below
Tracer-Dilution Method
Cl analysis:
◦ Filtered and stored w/o light, few months
◦ Dionex ion chromatograph
Na analysis:
◦ Filtered and stored w/o light, few months
◦ Spectrophotometer
Rhodamine WT analysis:
◦ Stored in glass bottle w/o light < 10d
◦ Fluorescence measured, Fluorometer
Current-Meter Method
Discharge measured with current meter
◦ Three sampling days
◦ Two measurements/site/day
Modified 4 locations
Depth and ave. velocity
◦ Measured at 17 to 25 vertical sections
Stream discharge determined by summing
flows through each measured subsection
Tracer (Chloride) Concentrations
Current-meter Discharge Data
Method Comparison
Method Comparison
Method Comparison
Discussion
Calculated discharges:
◦
◦
◦
◦
Current-meter 13.0 L/s
Tracer (25m) 15.9 L/s
Tracer (300m) 14.4 L/s
Average 13.0 L/s
Discussion
Gravel zone = 25% of channel flow
Gravel moves in and out between the
surface water and gravel zone
Current-meter = surface flow only
Tracer 300m = most mixing
Conclusion
Water in gravel zone moves down
channel as underflow
◦ Can be measureable
Affects discharge measurements
Tracer-dilution and current-meter
methods can yield different values
Tracer-dilution method yields different
results over different stream lengths
Testing and Comparison of Four Ionic Tracers to
Measure Stream Flow Loss by Multiple Tracer
Injection
Gary W. Zellweger
(1994)
Purpose of Study
Toxic metal transport, need to know
◦ Where stream is losing water
◦ How much water is being lost
Calculate discharge for 4 tracers used in
simultaneous multiple tracer dilution
◦ Li, Na, Cl, Br
Define limitations of method
Site Description
St. Kevin Gulch, CO
3rd order stream
◦ Flat, wetlands source
◦ Summer flow =
10 L/s
pH ~3.6 in August
Study reach = 570 m
◦ Upper stream = forested, steep, narrow
◦ Lower stream = smaller gradient, little vegetation,
minimal hillslope
Study Description
Tracer solution
continuously injected
at 5 wells
◦ Lithium chloride and
sodium bromide in
stream water
Injection sites
~100m apart
Parshall flumes
installed, 4 sites
Parshall Flume
Results
Only 3 injection sites operated at a time
Results
Results
Discussion
Precision of 2%
Discharge decreasing downstream (8%)
More effective to use different tracers at
each injection site
All tracers were conservative in St. Kevin
Gulch (116m reach)
4-18% difference in discharge
measurements between flume and tracers
Evaluating the Reliability of the Stream Tracer
Approach to Characterize Stream-Subsurface
Water Exchange
Judson W. Harvey, Brian J. Wagner and Kenneth E Bencala
(1996)
Quantifying Hyporheic Interactions:
An in-depth look at three studies
Geology 230, CSUS, Spring 2013
Presented by
Emily Siegel and Jessica Bean