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Tracer Test

An extensive 4-km tracer test was designed, coordinated, and carried out by Rob Ryan. Reconnaissance field work was carried out in March 2007; dye tests to approximate travel times were carried out in May, 2007; the actual field test was carried out from August 1 - 9, 2007 under low flow conditions. The test was repeated May 22 - 31, 2008 under higher base flow conditions.


Location map for tracer test.

Tracer Test Summary

• Preliminary colorimetric tests carried out in May 2007 to approximate total travel time and to design test
• Tracer test conducted over approximately 4 km reach from Aug 1-9, 2007
• Test broken up into two parts, one downstream, then one upstream
• Bromide injection used; rhodamine dye used simultaneously to colorimetrically check for first arrival to set ISCOs
• Field deployment was 24/7 for 9 days; 43 person-slots of help (paid+ volunteer)
• No rain; flows very low
• Test conducted over a pattern of four different land uses/land cover types
- Park/forest, older residential, heavy commercial, mixed light commercial/residential
•  Hypothesis is that hyporheic exchange will vary as a function of stream conditionrelated to land use
• 1200 samples collected
• IC analysis of all samples
• OTIS model being calibrated to data
• Results will be used as one input to groundwater model
• Test were repeated May 22-31 2008 under higher base flow conditions; 1400 samples  analyzed on the IC.
• Results presented at Fall 2008 AGU.
• Two manuscripts were published - one on results and one on methods.

Tracy Kerchkof and Phil Larson preparing bromide injection solution.
Rob Ryan carrying out dye test check.
Sarah Poole taking flow measurements with Chrissy Runyan.
Peter Lapa-Lilly assisting Rob Ryan with mixing up the bromide solution.