Latest Round of Herbicide Spraying Begins on

By Terry Witt Senior Staff Writer

The Fish and Wildlife Conservation Commission will spray more than 1,000 gallons of herbicide on portions of Lake Rousseau from July 6-17 in an effort to control invasive aquatic weeds, a practice that has drawn criticism from citizens of the area, but FWC says aquatic herbicides are the only effective way to control weeds at this time. John Kunzer, an invasive plant management biologist with FWC said Lake Rousseau is strewn with underwater stumps that make mechanical harvesting of the aquatic weeds extremely difficult and unsafe, and he said drawing down lake levels to expose large sections of the lake bottom could stop water flow to the Lower Withlacoochee River if additional water isn’t pumped to the river. Stopping the flow of water to the lower river could potentially cause saltwater intrusion to homeowner wells and the river. FWC plans to spray 1,400 gallons of Aquathol subsurface herbicide on portions of the lake to open boat trails clogged by hydrilla. It also plans to spray a quart-and-half of Galleon herbicide per acre and about two ounces of the herbicide Clipper per acre to eliminate floating aquatic weeds. Lake Rousseau is a freshwater impoundment formed 106 years ago when the Inglis Dam was built to produce electricity. The dam stands at a different elevation than the newer Inglis Bypass Canal nearby. The bypass canal pours water from the lake into the Lower Withlacoochee River. The difference in elevation prevents the use of draw downs to kill aquatic weeds, Kunzer said. Lowering the lake below 7 feet would dry up the flow to the lower river. “They would have to carefully pump water over the bypass canal as the lake was being lowered. Otherwise there would be no water getting to the lower river,” Kunzer said. Kunzer said he has often heard Lake Rousseau compared to Rodman Dam, an inland bass fishing destination, but he said the two lakes are different. He said Rodman Dam is an inland lake that isn’t affected by saltwater intrusion when water levels are drawn down. The Lower Withlacoochee River, on the other hand, empties into the Gulf of Mexico, a potential source of saltwater intrusion during a drawdown of Lake Rousseau. Lake Rousseau is fed by the and Withlacoochee River and has long been considered a good bass fishing lake, but some local fishermen say herbicide spraying has ruined the fishing in recent years. Kunzer said he has photographs of Lake Rousseau in the 1960s when the lake was entirely covered by invasive aquatic weeds. In the modern era, the lake is sprayed with herbicides to control floating weed islands known as tussocks, along with hydrilla and water lettuce. Kunzer said FWC doesn’t have authority to control water levels on Lake Rousseau. The authority rests with the Southwest Florida Water Management District (SWFWMD). SWFWMD produced an operations and management study in 1989 that recommended using “periodic draw downs” to control invasive aquatic weeds in Lake Rousseau. The study concluded that modifying water control structures on the Cross Florida Barge Canal below the Inglis Dam would allow lowering the lake for weed control and would offer sufficient flow to the lower river to prevent saltwater intrusion. Kunzer said making such modifications would be expensive. FWC doesn’t have authority to make modifications to a water control structure on the barge canal. Dan Hilliard, an official with the private group, Withlacoochee Aquatic Restoration (WAR), said making modifications to water control structures on the barge canal for the purpose of allowing draw downs on Lake Rousseau makes sense to him. He said he believes a structure could be built that intercepts water flowing over the Inglis Dam and diverts it to the Lower Withlacoochee River. The added water in the lower river would help maintain flow during draw downs. WAR is funding a study to determine why the Lower Withlacoochee River is dying. Herbicides from Lake Rousseau are thought to be one cause. Another possibility is the lack of flow in the lower river. He said one possibility for increasing flow would be to divert water to the Lower Withlacoochee from two sources invisible to the naked eye. He said water from a sinkhole that pushes water under the Inglis Dam could be diverted to the Lower Withlacoochee to add flow, and he said fresh water from 35 to 50 “seeps” and gushing springs on the floor of the barge canal could be channeled to the lower river. “You could potentially divert 60 to 70 million gallons of water daily to the lower river,” Hilliard said, making draw downs possible. The 1989 study by SWFWMD said Lake Rousseau was rapidly developing into a marshy area as a result of floating tussock islands, dense stands of hydrilla and stumps that obstructed water flow and accelerated the growth of tussocks. The study concluded that “substantial modifications” to the U.S. Army Corps of Engineers water control structures below the dam offered the best method for drawing down lake levels to achieve weed control and monitoring the flow of the lower river. Hilliard said SWFWMD has offered to assist WAR and DEP in its study of the Lower Withlacoochee River. He said the assistance of the Florida Department of Environmental Protection and the water district will substantially lower WAR’s costs for the study of the Lower Withlacoochee. He said the organization is amending its request to the Levy County Commission for RESTORE ACT funding to pay for the study. He said the reduction in costs is the reason for the amendment. “I’m optimistic. I think what we’re doing will fly,” Hilliard said.