State officials may have solved the puzzle of how zebra mussels got into the Colorado River.<\/p>\n
On July 3, Colorado Parks and Wildlife officials discovered a large number of adult zebra mussels in a privately owned body of water in western Eagle County. On July 28, Madeline Baker, an invasive species specialist with CPW, told members of the Colorado Basin Roundtable they believe this private lake is an upstream source of the mussels that have contaminated the Colorado River, the Government Highline Canal, Highline Lake and Mack Mesa Lake.<\/p>\n
\u201cWe do believe this to be the primary source, but it could now have created other secondary sources downstream with locations that hold water,\u201d Baker said. \u201cThere is a lot of speculation of could these veligers survive the journey from Eagle County down to Highline and create a new population there or is there some sort of intermediate population in between. So we still have a lot to figure out.\u201d<\/p>\n
<\/p>\n
Colorado Parks and Wildlife sampling on the Colorado River found zebra mussel veligers. The river is now considered \u201cpositive\u201d for zebra mussels from its confluence with the Roaring Fork River to the Utah state line. The discovery of the source pond for the mussels in Eagle County is a step in the right direction, but it doesn\u2019t mean the fight against zebra mussels is over.<\/p>\n
Photo courtesy of Colorado Parks and Wildlife<\/p>\n
Baker said that the lake\u2019s owner is collaborating with CPW on a mitigation plan. CPW is not releasing the owner\u2019s name or specific location of the lake.<\/p>\n
\u201cThe property owner is unsure of how this could have happened, but is being cooperative,\u201d she said.<\/p>\n
Baker said there were quite a few dead shells on the shoreline of the private lake, which indicates the zebra mussel population has been there for several years. She said CPW staff found the lake by searching Google maps for bodies of water on private property near the Colorado River and then calling property owners and asking if they could inspect their lakes. An outlet from the lake was bringing zebra-mussel-infested water into the Colorado River, an issue that has since been fixed.<\/p>\n
<\/p>\n
An adult zebra mussel found at Highline Lake in 2023. The lake was treated with a copper solution and drained for the 2024 boating season in an effort to eradicate the invasive species.<\/p>\n
Photo courtesy of Colorado Parks and Wildlife<\/p>\n
\u201cWe\u2019ve done a dye test at the reservoir to be sure that nothing more is flowing into the river, and that dye test showed us that it should be contained at this point, which will allow us to pave a path toward mitigation,\u201d Baker said.<\/p>\n
Zebra mussels are a prolific invasive species that if left unchecked could clog irrigation infrastructure, and strip the plankton and nutrients from the water. Once established, they are nearly impossible to eradicate.<\/p>\n
For the past two summers, microscopic zebra mussel larvae, known as veligers, have been found in the Colorado River at several locations. In June, they were found at the boat launch in New Castle, in Highline Lake and Mack Mesa Lake. The Colorado River is now considered \u201cpositive\u201d for zebra mussels from the confluence with the Roaring Fork River to the Colorado-Utah border.<\/p>\n
GRAND VALLEY THREAT<\/p>\n
The arrival of zebra mussels has been especially alarming for the Grand Valley, which is one of the most important agricultural areas and home to the biggest agricultural water users of Colorado River water on the Western Slope.<\/p>\n
\u201cAt least from a Grand Valley perspective, we feel like we are under a very serious threat,\u201d said Kirsten Kurath, a Grand Valley attorney and vice-chair of the roundtable.<\/p>\n
Adult mussels were found in 2022 in Highline Lake near the Utah state line. Officials treated it with a form of copper that kills zebra mussels called EarthTec QZ and drained it for the 2024 boating season. The lake reopened for recreation this year but on June 10, CPW staff found more veligers in Highline Lake, which is now designated an infested body of water. Highline Lake is filled with water from the Government Highline Canal, which pulls water from the Colorado River.<\/p>\n
\u201cWe now know that Highline Lake was continuously being reinfested with mussels after the treatment, so it\u2019s difficult to ascertain the effectiveness of the treatment,\u201d Baker said.<\/p>\n
<\/p>\n
In this file photo from June 2023, Highline Lake State Park employee Ryan Knight runs his hand under a boat surface checking for invasive mussels at the boat inspection site.<\/p>\n
Dale Shrull\/The Daily Sentinel<\/p>\n
Veligers were also found last year in the Government Highline Canal, which brings water from the Colorado River to Grand Valley farms, vineyards and orchards. Realizing the mussels could be disastrous for commercial peach growers who use micro-drip irrigation, water managers sprang into action last fall, treating their systems with a copper solution that kills the mussels.<\/p>\n
Grand Valley Water Users Association General Manager Tina Bergonzini said the copper treatment was successful \u2014 the irrigation company has not seen any signs of adult mussels in their system \u2014 and the Government Highline Canal has not had any more positive tests for veligers. Still, Bergonzini said GVWUA will probably do the copper treatment again this fall, and that preventing zebra mussels from becoming established is something they will be working on for the foreseeable future.<\/p>\n
\u201cI don\u2019t think there is any way around (doing the copper treatment again),\u201d Bergonzini said. \u201cWe can\u2019t risk our infrastructure. It\u2019s a financial hurdle for the irrigation companies because it\u2019s very costly, but not as costly as having fouled infrastructure.\u201d<\/p>\n
<\/p>\n
Leah Thomas from Highline Lake State Park conducts a decontamination of a boat at the lake on June 17, 2023.<\/p>\n
Dale Shrull\/The Daily Sentinel<\/p>\n
The discovery of the source pond in Eagle County is a step in the right direction, but it doesn\u2019t mean the fight against zebra mussels is over. CPW will continue sampling and mitigation work, Baker said.<\/p>\n
\u201cFinding the source was always the main focus,\u201d Bergonzini said. \u201cThere\u2019s no way you can win the war if you can\u2019t figure out where they are coming from. So I think discovering that pond was huge. That gives us a really good chance.\u201d<\/p>\n
CPW says cleaning, draining and drying fishing gear, motorized boats and hand-launched vessels like paddle boards is key to preventing the spread of invasive species.<\/p>\n