The Boulder Reservoir is facing a significant challenge with the invasive aquatic plant, Eurasian watermilfoil, which has rapidly spread since its identification in 2022. The plant's extensive growth, particularly in the Western Coves, has raised concerns about decreased boating access and swimmer safety. If left unmanaged, Eurasian watermilfoil could negatively impact water quality and regional water supply.

In response, the city of Boulder, in collaboration with Northern Water, has developed an adaptive management plan aimed at controlling the invasive species. This plan includes routine surveys to monitor watermilfoil populations, manual removal efforts by Parks and Recreation staff, and the strategic application of selective herbicides. The herbicide Triclopyr has been recommended due to its effectiveness and minimal risk to water quality and recreation.

City officials are targeting a spring 2025 application for the herbicide, with a focus on timing it to coincide with lower recreational use to minimize impact on the public. The management strategy aims for a significant reduction in watermilfoil populations, although complete eradication is not expected. The long-term goal is to transition away from herbicide reliance by integrating alternative management strategies.

Further strategies under consideration include water level management and the installation of permanent bottom barriers, though these require additional feasibility evaluations and funding. Community outreach will be a key component of the management plan, ensuring that residents and downstream users are informed well in advance of any herbicide treatments.

City staff will continue to provide updates to the community as they finalize the details of the management plan, emphasizing the urgency of addressing the invasive species to prevent further ecological and recreational impacts.