The U.S. Geological Survey will be conducting a dye-tracing study in the Fraser River between Oct. 28 and Nov. 1, according to a press release from the agency. During this time, a nontoxic dye called sodium fluorescein will be introduced into the river between 3 and 7 p.m. The dye will be monitored through the night as it flows downstream.

Dry conditions are necessary to complete the study. The agency expects to conduct the study Oct. 29, weather permitting.

This study will help researchers understand how and where groundwater flows into the Fraser River. Sodium fluorescein is an environmentally safe dye, according to the U.S. Geological Survey, and is commonly used in hydrologic studies. The dye will be released as a slow continuous drip for 4–10 hours near Confluence Park in Winter Park.

Water specialists will monitor the dye’s progress at various downtown locations.

Following the dye injection, the water might appear light yellow to green for 12–24 hours afterward. Researchers are expecting little to no color change in the river south of the confluence between the Fraser River and St. Louis Creek during the monitoring period.

This study is part of the U.S. Geological Survey’s research to identify potential groundwater inflow locations and estimate groundwater contributions to the Fraser River, according to the press release. These estimates can be used to understand the sustainability of streamflow and groundwater flow under changing climate conditions.

The town of Fraser, the town of Winter Park, Grand County and Trout Unlimited all gave the U.S. Geological Survey permission to conduct the test.

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