Highline Lake will be lowered about 30 feet over the next few months as efforts continue to eradicate zebra mussels in the lake and stop their spread into other waters.

“The next phase to remove zebra mussels from Highline Lake will be twofold,” said State Park Manager Alan Martinez. “Our goal is to eliminate the mussels while protecting a quality warm water fishery that has taken decades to build.”

Highline Lake will be lowered an additional 20 feet from the initial lowering that began Nov. 28 to inspect the pump at the inlet that pulls water from the reservoir into the Government Highline Canal.

In addition to lowering the lake to expose areas along and near the shoreline to kill zebra mussels through the natural processes of desiccation and freezing, Colorado Parks and Wildlife will apply EarthTec QZ, a copper-based molluscicide, to the lake.

Once the lake has reached the desired level and the ice has come off the lake, CPW will perform the first application of molluscicide to the east side of the lake. Park staff believe this will occur around March 1. After two weeks, a second application will be added to the west side of the lake.

Robert Walters, invasive species program manager for Colorado Parks and Wildlife, said attempting eradication while population densities remain low offers the best opportunity to eradicate the mussels and prevent their spread to other waters in the state.

This two-step application approach will allow fish and other aquatic species the ability to move to areas of the lake where concentrations of the chemical are initially lower. Water from the canal will be turned back on in April, with Highline Lake returning to normal levels around the first week of May.

Colorado Parks and Wildlife will continue to monitor Highline Lake for the presence of zebra mussels on a weekly basis following the treatment. Even if no evidence of zebra mussels are found in the first year, Highline Lake will be considered infested for five years. If no zebra mussels or other aquatic nuisance species are found during this time, the lake would return to a negative prevention water and the containment boat inspection and decontamination program that began in September will no longer be required.

“We are optimistic that with the combination of lowering Highline Lake and the EarthTec QZ application, we will be able to eradicate the mussels while limiting impacts to non-target organisms, including preservation of the warm water fishery that Northwest Region staff have worked so hard to build,” Walters said.