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Reporters: If interested in being notified when the study date is chosen, please contact Jennifer or Susannah.

U.S. Geological Survey scientists will inject a harmless, bright red fluorescent dye into the Yellowstone River during the week of June 26, 2017, weather permitting. The study is being done in cooperation with the U.S. Army Corps of Engineers and the Bureau of Reclamation.

The goal of the dye study is to understand how larval fish drift in the complex waters of the Missouri and Yellowstone Rivers. Such information is used by federal, state and local agencies to help manage aquatic habitat and water resources.

The red dye—known as Rhodamine WT—will detect flow patterns in the Yellowstone River downstream from Glendive, Montana, during high flows in June. Rhodamine WT, which has been used in hydrologic studies for decades, is approved for use as a water tracer by the U.S. Environmental Protection Agency and is harmless to people, fish, and plants at the concentration being used for this study. After releasing the dye into the river at a central location near river mile 91 (downstream from Interstate bridge at Glendive), strategically placed instruments will track travel times and dispersion of dye downstream.

The start date will be determined based on local weather and flow conditions, and the study is expected to last four to six days. For a few hours after the start of the study, several miles of the river will appear reddish in color because of the dye. The red color will dissipate rapidly and will disappear after it travels several miles downstream. During the study, USGS will deploy multiple boats on the river to monitor the dye transport. The event will be closely monitored by USGS scientists to ensure dye concentrations do not exceed the EPA approved threshold of 10 parts per billion in the vicinity of water intakes.

This assessment of the Yellowstone follows a successful dye trace on the Missouri River in summer 2016 downstream from Fort Peck Dam.

Photo of a red dye-tracer study in June 2016 on the Missouri River near Fort Peck Dam, Montana.
USGS scientists conducted a dye-tracer study in June 2016 on the Missouri River about 10 miles downstream of Fort Peck Dam, Montana. The public can expect to see the Yellowstone River turn a similar color in the vicinity of the injection site when scientists conduct a dye study near Glendive, Montana in late June, 2017.(Credit: Pat Braaten, USGS. Public domain.)

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