Evaluating breakup discharge using fluorescent dye

February 28, 2013 • Filed under: News — melanie.rohr

WERC graduate student Nathan Stephan will discuss methods of using fluorescent tracers to collect river discharge information at this week’s seminar, Friday, March 1, 2013.

Friday Seminar Series

  • What: Utilizing Dye Tracers to Estimate River Discharge
  • Who: Nathan Stephan
  • When: 3:30-4:30 p.m., Friday, Mar. 1
  • Where: 531 Duckering

Dye tracer study being performed on the Itkillik River, July 2012

Discharge in Arctic rivers is often near its annual maximum during spring breakup. However, the presence of swiftly moving ice at this time of year leads to unsafe boating conditions, thus complicating the collection of discharge information through modern methods such as an Acoustic Doppler Current Profiler (ADCP). Beginning in September 2010, and resuming in May 2011, a field study was performed to evaluate the breakup discharge of Alaska’s Itkillik River using RhodamineWT, a fluorescent dye. Our studies were based upon the slug-injection method outlined in the USGS paper “Measurement of Discharge Using Tracers” (1984). Notable advantages of the method included the ability to inject and collect the dye without entering the water. A disadvantage of the method was the confounding effects of turbidity and/or suspended solids. In our 2012 field season, a second fluorescent dye, Uranine, was utilized in field studies on the Itkillik and Upper Kuparuk Rivers. The results indicated that the Uranine did not encounter the sorption issues we faced with RhodamineWT. With improvements made to our sampling techniques and the addition of Uranine, which proved to be a viable tracer for surface water discharge, to our tracer studies, we were able to see a vast improvement in our discharge results resembling those recorded by the ADCP.

Our current work includes applying these same dye tracer techniques to investigate under-ice flow measurements, as well as fabricating an automated sampling system that would allow for either a slug-injection or constant-rate injection method.

Photo above: Dye tracer study being performed on the Itkillik River, July 2012.

(Photo by Nathan Stephan)