LAKE COUNTY — Bright purple spray to control aquatic weeds at points around Clear Lake may become a more common sight as temperatures rise, according to county officials. Private dock owners have begun hiring contractors to spray the water for aquatic weeds.
The purple spray is copper, one of six chemicals used to kill weeds that clog boat ramps and swimming areas when the lake water is clear and allows photosynthesis at greater depths, according to Skip Simpkins of Lake County Lakebed Management. The county Water Resources Department has issued 50 permits to licensed sprayers since January, according to Deputy Director Pam Francis.
According to Record-Bee outdoor columnist Terry Knight, dock owners approach him every year when spraying begins wanting to know what is going on.
“The reason it is done is to open up the recreational areas for water use,” Public Services Director Kim Clymire said. Clymire hires sprayers to unclog boat launch and swimming areas at Lakeside County Park in Lakeport, Keeling Park in Nice, Lucerne Harbor Park and public access points between Lucerne and Glenhaven along Highway 20.
Simpkins said the weeds proliferate when algae are minimal and the water is clear, as it is this year. The water may be clear this year because lack of rainfall in late spring meant less nutrients to cloud the water and less algae growth, according to Simpkins.
“That allows light to penetrate to the bottom and germinate the seeds that are lying there dormant,” Simpkins said. He said the sunlight can reach depths of up to 12 feet.
“Years ago, it went out a quarter mile in some areas. This year could be the same. The lake is a dynamic structure, and we have problems predicting from year to year for weed growth,” Simpkins said.
Agricultural Commissioner Steve Hajik said of six different chemicals used, copper is the most common because it is the most cost-effective and works quickly, taking two to three days to take effect.
Spraying presented a problem two years ago, when approximately 2,000 fish died from lack of oxygen during hot weather, as Knight reported in an Aug. 9, 2006 column. More than half of them were carp, he said, but at least 500 were largemouth bass, crappie and catfish.
“What happens is that when plants die from being sprayed, they use up oxygen, which has an effect on fish. They don”t die from the herbicide, they die from a lack of oxygen,” Knight said.
“If you kill too many weeds at one time, they all die and begin decomposing, which uses oxygen and depletes the oxygen in the water. But fish are not dumb and they usually go someplace else,” Francis said.
She said sprayers must adhere to a patchwork pattern when spraying so that fish can move from one area to another.
Francis said the county Water Resources Department has a state permit from the California Regional Water Resources Control Board that restricts when spraying can happen. Spraying is not allowed when dissolved oxygen levels are below five parts per million or when the water temperature is above 80 degrees, according to Francis.
The county Public Services Department didn”t do any spraying last year because the weeds bloomed in late fall, after the peak tourist season, according to Clymire. He said the last contract he signed for spraying two years ago was for approximately $15,000.
“I didn”t see any reason to, one, spray unnecessarily or, two, spend money unnecessarily,” Clymire said. “We”re already seeing them just below the surface in most areas. It”s probably going to be problematic this year.”
The most heavily affected areas include shoreline from Lakeport to Rodman Slough, and areas where the water is calm in Nice and Lucerne, according to Simpkins.
A permit costs $100, less than a fourth of the county”s cost for water testing to meet state requirements. The number of permits issued annually is on the decline, according to Francis. She said the county issued 198 permits in 2002, down to 86 in 2007. She said the number is expected to stay the same this year.
Contact Tiffany Revelle at trevelle@record-bee.com.
