Testing, testing, 1-2-3: How data guides efforts to protect Owasco Lake

You can live near a lake your whole life and never really know it. Drink its water from the tap; swim in it; fish from it; ride fast or slow across its surface. You can gaze into the lake from your boat and realize that even when the water seems clear, you can’t see very far down.

Owasco Lake is not just a giant bathtub. It’s a complete and complex ecosystem filled with living and non-living components that work together as a unit. In recent years, many people have noticed the lake changing from how they recall it in the past. It may not freeze over completely in winter. More lake plants grow around people’s docks in summer, and public swimming beaches have closed because of harmful algal blooms. We worry; how is Owasco Lake doing? Is it thriving or in trouble?

We are extremely fortunate that Owasco Lake was studied for 20 years by the Finger Lakes Institute at Hobart and William Smith Colleges in Geneva. FLI’s team, led for most of that time by Dr. John Halfman, monitored the lake at sites off- and near-shore and via a mid-lake buoy. The FLI team has shared its findings at the Owasco Watershed Lake Association’s annual Bob Brower Scientific Symposium. This work has been funded by many sponsors, including OWLA.

Additional data from other reputable sources strengthens our understanding. But scientific research is expensive and time-consuming. Trained citizen scientists can provide more “bang for your buck” by extending the professionals’ reach out in the field. Two New York State Department of Environmental Conservation programs that OWLA commits to are the Citizen Science Lake Assessment Program and the New York Harmful Algal Blooms System. Both programs add to FLI’s earlier work and may help us better understand the factors underlying the increasing number of harmful algal blooms seen in Owasco Lake, arguably its most serious health challenge.

CSLAP is a volunteer lake monitoring program run by the state DEC and administered by the New York State Federation of Lake Associations. Lake association volunteers are trained to collect water samples by boat a minimum of four times each season, once per month from June through September at the deepest part of the lake.

In 2017 the DEC rallied for all 11 Finger Lakes to join the CSLAP program and utilize the same state Environmental Laboratory Approval Program-certified lab, Upstate Freshwater Institute in Syracuse. This arrangement supports consistent methodology for the region. In Owasco Lake, OWLA volunteers monitored one sampling site with a sounding depth of about 174 feet. Along with weather and lake recreation observations, they took air and surface water temperatures and water clarity readings. Water samples were drawn at two depths, about 5 feet and about 28 feet, processed onshore for a variety of tests for inorganic and organic compounds, and transported to the Syracuse lab.

OWLA’s second major in-lake volunteer effort is with NYHABS. The program began in 2014. In its present form since 2017, about two dozen trained OWLA volunteers upload visual and digital data to an interactive map on the DEC’s website. Volunteers are assigned to lakeshore zones they monitor weekly from early July through mid-October. Members of the public may also upload data when they encounter a suspicious bloom on the lake. The included graph from NYHABS shows Owasco Lake’s reported blooms from 2015 to 2024.

A lake’s health can be assessed in many ways. Factors involving harmful algal blooms include surface water temperature, phosphorus, chlorophyll and water clarity. FLI’s 2022 report highlighted a trend toward warmer surface water over the past two decades, as has been documented over the wider Finger Lakes region. Because HABs occur more often in warm, calm water, warmer lake surface temperatures increase the likelihood of HABs developing.

Although phosphorus levels generally are low in the Finger Lakes, including Owasco Lake, phosphorus is a key nutrient that can fuel algal and HAB growth. While the FLI 2022 report shows that phosphorus levels entering the lake have decreased since 2016, DEC data, including CSLAP results, shows that total phosphorus levels have remained somewhat stable for 30 years. It is notable that phosphorus stored in lake bottom sediment can be released back into the water, compounding the issue.

The presence of chlorophyll in a lake is a measure of algae abundance of all kinds, with lower concentrations indicating clearer water. Chlorophyll levels in Owasco Lake have remained moderate and stable over the past three decades, based on data available from the DEC. Water clarity in Owasco Lake follows this trend, averaging about 6 to 12 feet. Clear water down to those depths indicates the moderate presence of living and nonliving particles in the water. Moderate levels don’t sound too bad, but people recreating in the lake likely prefer clearer water free of plant and algae growth.

The end goal of all this data collection is to support lake management plans that aim to bring Owasco Lake back to optimal conditions for drinking water, fishing and recreation. Solutions for keeping our lake healthy are only as successful as the buy-in from the whole community that depends on the lake’s well-being. Ten or 20 years of research might sound like a long time to us, but it is negligible in the life of a lake. We don’t want to waste time or money, but we do want informed action. If we want to know, we must keep looking.

Julie Lockhart is secretary of the board of directors of the Owasco Watershed Lake Association.