Half Moon Lake getting chemical treatment Wednesday - WQOW TV: Eau Claire, WI NEWS18 News, Weather, and Sports

Half Moon Lake getting chemical treatment Wednesday


Eau Claire (Press Release) - The City of Eau Claire, in partnership with the state Department of Natural Resources and the U.S. Army Corps of Engineers, is poised to launch the fifth year of a plan to reclaim Half Moon Lake from an infestation of invasive plants.

Half Moon Lake in Eau Claire will be treated with Aquathol K on Wednesday, May 15, 2013. No boats will be allowed on the lake during the application. There are no restrictions on use of the lake for swimming or fishing after the application. Use of lake water for irrigation should be suspended for 14 days after the application. The herbicide will be applied by Lake Restoration of Rodgers, Minnesota, under the supervision of the Wisconsin Department of Natural Resources and the US Army Corp of Engineers/Eau Galle lab. The herbicide is being applied under DNR permit #WCR-12-18-91, awarded to the City of Eau Claire.

This specialized herbicide treatment is the fifth application of five consecutive years of herbicide applications.  The application is designed to eradicate, to the greatest extent possible, the curlyleaf pondweed that has long dominated the entire lake. No Eurasian watermilfoil was found this spring in the lake, so treatment for that invasive plant will not be required this year. The treatment is not expected to harm native aquatic plants.

For years the explosive growth of curlyleaf pondweed each spring has resulted in poor water quality for recreational lake users while preventing the growth of native plants important to the lake's locally treasured populations of game fish. Eurasian watermilfoil  expanded its grip on Half Moon, threatening to choke off large sections of the lake and overtake more native plants, but was effectively eliminated after the 2009 herbicide treatment.

The problems afflicting Half Moon can be traced back for more than a century when oxen used by loggers wintered on the lake ice, contributing huge amounts of fertilizer to the lake bed each spring.  Decades of urban runoff contributed more nutrient pollution before officials gained greater control over storm water. 

The invasive curlyleaf pondweed, which has multiple means of reproducing, exacerbated the problem.  These plants pull large amounts of phosphorous from the nutrient-laden lake sediments and when they die back and break up each June they release phosphorous into the open water, just in time to stimulate summer algae blooms.  Decomposing algae then removes dissolved oxygen from the bottom waters of the lake and starts a chemical chain-reaction that releases still more phosphorous from the sediments.

This is not the first effort to save Half Moon Lake.  For five years, ending in 2007, the city conducted an annual harvest of curlyleaf pondweed each spring in an effort to control its growth.  The effort proved to be inadequate.  Each curlyleaf pondweed plant annually releases hundreds of propagules, ensuring dense growth for up to five years.

The proposed herbicide treatment contains the herbicide known as brand name "Aquathol K". This herbicide treatment has proven successful in several Wisconsin and Minnesota lakes.  The herbicide is being applied now as the water temperature of Half Moon Lake is between 53-59 F (12-15 C).

Adjoining property owners will be asked to not water lawns or gardens for 14 days after the herbicide application. 

Half Moon Lake, 154 acres of water in the shape of a horseshoe, surrounds Carson Park within the City of Eau Claire offering area residents a beautiful natural resource for fishing, water recreation and relaxation.  City officials have developed this plan so the lake will continue to enrich the lives of city residents for generations to come.


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