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October 27, 2022

Crested Butte, Colo — The U.S. Geological Survey will be conducting a non-toxic dye-tracing study in the Slate River, north of town, between Nov. 1 and 4, 2022. During this time, fluorescein, a green, non-toxic dye, will be introduced into the river between 3 and 7 p.m. and monitored through the night as it flows downstream. 

The dye will be released as a continuous slow drip for approximately 4 to 10 hours at a location near the Oh-Be-Joyful Campground and monitored at downstream locations by USGS hydrologists. Dye injection may result in a light yellow to green color visible in the river for approximately 12 to 24 hours afterwards. Scientists will inject the dye in the late afternoon to avoid turning the river green during high-usage hours. It is expected that minimal to no change in color will be visible in the river to the south (downstream) of the Peanut Lake area during the monitoring period. 

The study is part of ongoing work by the USGS to help identify groundwater inflow locations and estimates to the Slate River between Oh-Be-Joyful Campground and the town of Crested Butte. These estimates can be used to understand the sustainability of streamflow and groundwater discharge under changing climatic conditions. The USGS is working with the U.S. Bureau of Land Management, the Crested Butte Land Trust and the Rocky Mountain Biological Laboratory to conduct the research. 

Information on USGS studies of water resources in Colorado is available at

The USGS provides science for a changing world. Learn more at or follow us on Twitter @USGS, Instagram @USGS or Facebook @USGeologicalSurvey


Fluorescein dye in Wind Cave

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