During this time, a non-toxic green dye, fluorescein, will be introduced into the Creek between 3 and 7 p.m. and will be monitored through the night as it flows downstream. Findings will help researchers understand how water from the historic Sugarloaf mining district flows into Lake Fork Creek. 

 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 about 400 meters downstream from the Sugarloaf dam in Lake Fork Creek. USGS hydrologists will monitor its progress at various downstream locations to conduct this study. 

Dye injection at the creek 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 late afternoon to minimize coloration of the river during high-usage hours. Researchers expect little to no visible color change in the creek south (downstream) of Halfmoon Creek during the monitoring period. 

This study is part of the USGS's ongoing research to identify potential groundwater inflow locations and estimate groundwater contributions to Lake Fork Creek. The focus area extends up to 600 meters (1/3 of a mile) downstream from Sugarloaf Dam.  

The USGS is working in cooperation with the Bureau of Land Management, the State of Colorado, Trout Unlimited, the Natural Resource Damage Trustees of the California Gulch Superfund site, and the Arkansas River Watershed Collaborative. The USGS has received permission to conduct the dye-tracing study from the Bureau of Land Management, Lake County Commissioners, Lake County Community Planning and Development, and private owners of the Lake Fork Ranch Company. 

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