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