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Comparison of Tracer-Dilution and Current-Meter Measurements in a Small Gravel-Bed Stream, Little Lost Man Creek, Cal

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:

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Comparison of Tracer-Dilution and Current-Meter Measurements in a Small Gravel-Bed Stream, Little Lost Man Creek, Cal

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  1. 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)

  2. 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

  3. Background • Current-meter technique preferred method to determine discharge • Issues with current-meter method: • Shallow depths o Rough bottom • Flow through gravel o Discharge variation • Continuous tracer-dilution methods can accommodate these factors

  4. Tracer-Dilution Method • Can be used to calculate discharge at multiple sites • Requirements: • Tracer thoroughly mixed with stream • Conservative tracer

  5. Tracer-Dilution Method …Plateau Concentration • Can be used to calculate discharge at multiple sites • Requirements: • Tracer thoroughly mixed with stream • Conservative tracer Tracer injection. Concentration rises to…

  6. Tracer-Dilution Method • Can be used to calculate discharge at multiple sites • Requirements: • Tracer thoroughly mixed with stream • Conservative tracer

  7. 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

  8. 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

  9. 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

  10. 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

  11. 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

  12. Tracer (Chloride) Concentrations

  13. Current-meter Discharge Data

  14. Method Comparison

  15. Method Comparison

  16. Method Comparison

  17. 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

  18. 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

  19. 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

  20. Testing and Comparison of Four Ionic Tracers to MeasureStream Flow Loss by Multiple Tracer Injection Gary W. Zellweger (1994)

  21. 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

  22. 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

  23. 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

  24. Parshall Flume

  25. Results • Only 3 injection sites operated at a time

  26. Results

  27. Results

  28. 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

  29. 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)

  30. Quantifying Hyporheic Interactions:An in-depth look at three studies Geology 230, CSUS, Spring 2013 Presented by Emily Siegel and Jessica Bean

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