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Work group traces Grizzly Reservoir fish kill to naturally mineralized Lincoln Creek tributary; modeling planned
Summary
A Lincoln Creek work group convened by Pitkin County Healthy Rivers found that metals — especially copper — and high temperatures contributed to a 2021 fish kill at Grizzly Reservoir, with most metals coming from a naturally mineralized tributary rather than historic mining; the group sampled 54 sites across 40 tributaries and plans a hydrogeochemical model to test interventions.
Pitkin County Healthy Rivers and a Lincoln Creek work group reported that scientists traced a 2021 fish kill at Grizzly Reservoir to metals, notably copper, combined with elevated water temperatures, and concluded that nearly all of the metals originate in a naturally mineralized tributary of Lincoln Creek rather than from historic mining.
The work group conducted a synoptic survey sampling 54 sites and 40 tributaries from Upper Lincoln Creek above the Ruby Mine downstream to Grizzly Reservoir to create a systemwide snapshot of the watershed’s hydrology and water chemistry. That survey helped identify which tributaries were key metal sources and how each contributes to conditions downstream.
With those data as a foundation, the group plans to develop a hydrogeochemical model to simulate interactions between water and minerals across the watershed and to evaluate how different interventions could change water quality over time. The modeling is intended to give managers and partners a tool to test potential actions before implementation and to inform forward-looking decisions to protect aquatic life and water quality.
The presentation framed the effort as collaborative, bringing together scientists, agencies and community partners to understand the system and explore solutions. Protecting the Upper Roaring Fork watershed, the presenters said, will require using the survey results and modeling to guide interventions that reduce metal loads and manage water temperatures.
Next steps identified by the work group include the hydrogeochemical modeling phase and continued coordination among partners to translate findings into targeted actions to protect rivers and the communities that rely on them.
