Algae toxin monitoring resumes in Grand County water bodies
August 7, 2009
Blooms of blue-green algae (cyanobacteria) can release cyanotoxins into the water that are potentially harmful to humans and pets. Together with several agencies, Grand County is testing Grand Lake and Shadow Mountain, Granby, Willow Creek and Windy Gap reservoirs for cyanobacterial toxins.
If necessary, drinking water and recreational use advisories may be issued for affected areas. Lake residents may contact Katherine Morris, Grand County water quality specialist, at 970-725-3347 x158, or firstname.lastname@example.org if they would like to be notified directly of an advisory.
Water advisories pertain to anyone using water drawn directly from an affected water body, as well as to recreational users with physical water contact (swimmers, water-skiers, boaters), or accidental ingestion, on Grand Lake, Shadow Mountain and Granby Reservoirs, the Colorado River between Shadow Mountain and Granby reservoirs, Willow Creek Reservoir, and possibly downstream of Windy Gap Reservoir.
Cyanobacteria have been documented in the Three Lakes since the 1950s, though methods for detecting toxins only recently became available. In 2007, toxin levels were just above that which the World Health Organization says is safe for an adult to drink for a lifetime, and resulted in advisories to both drinking water and recreational users. As a precaution, in 2008, Grand County began weekly monitoring for cyanobacterial toxins from early July to September. Levels were very low throughout 2008.
Algae blooms in 2007 may be tied to the October 2006 drawdown of Shadow Mountain Reservoir to kill aquatic weeds.
“The only year we have documented elevated values of microcystin toxins is 2007, the year following the drawdown, when blooms were anticipated because of nutrient release,” says Morris. “We have no reason to expect that we will see such high numbers again, but we’re trying to be proactive.”
Temperature, sunlight, and nutrients all influence cyanobacterial growth.
Grand County, the Bureau of Reclamation, Colorado River Water Conservation District, Greater Grand Lake Shoreline Association, Northern Colorado Water Conservancy District, Three Lakes Watershed Association, and Town of Grand Lake are sharing the costs of the sampling and analyses.