During this time, a non-toxic dye, sodium fluorescein, will be introduced into the river between 3 and 7 p.m. and will be monitored through the night as it flows downstream. Findings will help researchers understand how and where groundwater flows into the Fraser River.  

The environmentally safe dye is commonly used in hydrologic studies and will be released as a continuous slow drip for approximately 4 to 10 hours at a location near Confluence Park in Winter Park. USGS water specialists will monitor the dye’s progress at various downstream locations to conduct this study.  

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Dye injection at the park may result in a light yellow to green color visible in the river for approximately 12 to 24 hours after the dye injection. The process will be initiated in the afternoon to minimize coloration of the river during high-usage hours. Researchers expect little to no visible color change in the river to the south (downstream) of the confluence between the Fraser River and St. Louis Creek during the monitoring period.     
 

The study is part of the USGS’s ongoing research to identify potential groundwater inflow locations and estimate groundwater contributions to the Fraser River.  These estimates can be used to understand the sustainability of streamflow and groundwater flow under changing climatic conditions.   

The USGS received approval to conduct the dye-tracing study by the Town of Fraser, Town of Winter Park, Grand County, Learning By Doing, East Grand Water Quality Board and Trout Unlimited.  
 
 

To learn more about water research in Colorado, visit the USGS Colorado Water Science Center website.