The Department of Ecology’s Intensively Monitored Watersheds study will be conducting a fluorescent dye time-of-travel study in Germany Creek and Mill Creek in Cowlitz County during the week of September 6, 2011.
The dye, Rhodamine WT, is red-orange. It is very visible at the point of injection, but disperses as it moves downstream. This is a harmless dye at the low concentrations we use, and is commonly used for this type of study. DOE tracks the dye with fluorometers installed at the upstream end and the downstream end of the reach. The fluorometers measure the concentration of the fluorescent dye, and the difference between the upstream and downstream dye concentration tells us how long it takes for the water to travel through the reach.
Now you know! Also, please note this is a "time-of-travel" study, not a "time-travel" study, which is what I thought when I first read the press release. I just wanted to save you the disappointment that I felt.