AUBURN — 2017 was a rough year for Owasco Lake, but John Halfman has some ideas for improving its water quality and keeping harmful algal blooms from turning its beaches to pea soup.
Halfman, professor of geolimnology and hydrogeochemistry at the Finger Lakes Institute at Hobart and William Smith Colleges, gave his annual lake water quality report Tuesday morning.
It started out bleak.
"The lake is under stress," he told members of the Owasco Lake Watershed Management Council. "Things are getting worse and worse if you look at the last decade of record."
Cyanobacteria, most often called harmful algal blooms, proliferated in the late summer and early fall, and Halfman said they tended to congregate on the northeastern shoreline.
Halfman called the trend "disturbing," and said he's reconsidering how the blooms get there. The traditional school of thought has been blooms can spring up in the lake's surface water, and winds carry them to shore. While wind patterns match up with where the blooms are spotted, Halfman said he's more and more convinced that wind churns up the blooms in open water and makes them disappear.
Cautioning that it's just an idea, Halfman said he thinks weeds and debris are getting blown to shore. When they accumulate and decay, they release more nutrients such as phosphorous, an ingredient needed in a recipe for harmful algae.
"What I've been wrestling with for a couple of years now is to get blooms of that size needs massive amounts of fertilizer, massive amounts of nutrients, and you can't get that at a nearshore location unless you get some sort of organic matter or bring something else," he said Tuesday. "This provides a mechanism to bring in more weeds to a given area, then rot, start to stink, release their nutrients, and then you get a bloom."
Halfman said lakeshore property owners should be encouraged to rake their shorelines of weeds. He said bubbler systems could be helpful in keeping the water churned up to avoid blooms. Mats could also be put down on beaches to keep vegetation from growing. Since Owasco Lake is a drinking water source, he said he would never promote the use of herbicides.
He did say, however, that Owasco Lake should have its own weed harvester boat. The Cayuga County Soil and Water Conservation District has one it uses to trim all of the county's water bodies of weeds, but with a top speed of 5 mph, it often can't get to each one in a summer.
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Besides decaying organic material, Halfman's report points to Dutch Hollow Brook, Mill Creek, Hemlock Creek and the Owasco Inlet as the main sources of nutrient loading into Owasco Lake.
Each of those tributaries sent 5 metric tons of phosphorous into the lake last year, showing nonpoint pollution is Owasco's biggest problem. Nonpoint pollution comes from many different sources and is usually caused by rain or snowmelt, according to the U.S. Environmental Protection Agency.
Meanwhile, Moravia and Groton's wastewater treatment facilities, which are considered point sources of pollution, discharged 0.1 metric tons of phosphorous to the Owasco Inlet last year.
Despite these numbers, Halfman pointed out that the lake actually lost about 0.3 metric tons of phosphorous last year.
"The decrease to near equilibrium conditions in 2016 and 2017 is encouraging, and perhaps Owasco Lake is responding to the performed remediation efforts," the report read, "but inputs must be much less than outputs to improve water quality."