Certainly, public opinion about the health of Cayuga Lake is varied.

A look at the lake can yield a cursory picture of its health.

Dave Openshaw, of Dryden, sails and swims in the lake nearly every day during warm weather, as he has for the past 11 years. For him, the lack of dead fish and fewer zebra mussels seem to indicate a healthy lake.

"I think the lake is in relatively good shape, but I try to avoid anywhere south of the sail club," he said.

Carol Katchmir of Spencer can vividly remember how the lake appeared when she took her children to Stewart Park 30 years ago. "I remember the water was scummy, green and yellow with so much algae. ... It seems so much clearer now," she said.

Studying the lake and collecting some data, the picture can become clearer.

Experts and 1998 data collected for the Department of Environmental Conservation say that Cayuga Lake is in relatively good condition. But there is still public concern about lake management and the potential effects of Cornell University's Lake Source Cooling Project.

Cayuga Lake is classified as mesotrophic by the DEC and other limnologists, meaning that it supports a moderate amount of algae, plants and other aquatic life forms and has somewhat unclear water.

But the picture is still not complete.

To understand the condition of the lake and predict its future, it's necessary to understand the abundance of human and natural factors affecting Cayuga Lake's ecosystem.

Some of these factors include sediment flow from the lake's tributaries, phosphorus levels, chlorophyll A levels, coliform bacteria from manure, runoff pollution, herbicides and pesticides and global climate conditions.

Assimilating the slew of data and historical information about the lake - and then making a plan for the future - is a taxing task.

The Cayuga Lake Watershed Management Plan, in conjunction with the Cayuga Lake Watershed Network, a nonprofit educational organization focused on watershed issues, began this information collection and analyzing process. It aims to release a watershed plan in August.

The plan will help communities around the lake identify priorities and make recommendations for their area of the watershed. It also will help protect public health as well as the lake's natural areas, and sustain the economic activity supported by the lake. All of the other Finger Lakes already have management plans completed or in progress.

Cayuga Lake, part of the chain of Finger Lakes with unique glacial origins and striking geologic features, is the longest and second-deepest of the Finger Lakes.

Its beauty swells the hearts of admirers and naturalists, prompting politicians and activists to advocate for its overall welfare and triggering breakthrough studies by scientists.

From far-fetched lore to picturesque scenes in local paintings, Cayuga Lake has long been a source of interest, recreation and passion for residents and visitors alike.

In a survey conducted by the Cayuga Lake Watershed Network, more than 75 percent of the 294 people polled named water quality and public health as the most important Cayuga Lake watershed issue.

While the DEC has listed the lake as requiring special monitoring, scientists, some government entities and others say water quality is good, although a consistent management plan is needed.

Several sources of contaminants are of concern: phosphorus levels from wastewater treatment plants; coliform and sediment levels from erosion; and development around the lake.

Nelson G. Hairston Jr., Cornell's F.H.T. Rhodes Professor of Environmental Science, who has intensively studied Cayuga Lake, said the public's concerns are primarily aesthetic, but they stem from the phosphorus and chlorophyll A levels in the lake.

Phosphorus is naturally present in lakes and limits the growth of algae, while chlorophyll A is the plant pigment indicating algae abundance. Both of these nutrients, he said, are not present in Cayuga Lake in any dangerous level.

The most recent data available on the levels of these nutrients in the lake comes from the Upstate Freshwater Institute, a Syracuse-based nonprofit research group hired by Cornell to monitor the lake and any changes that take place as a result of Lake Source Cooling.

The data show that the southern end of Cayuga Lake has slightly higher concentrations of phosphorus and chlorophyll A than the deeper water of the lake, especially in spots near the wastewater treatment plants.

"It is not that we shouldn't be concerned about these nutrients, but steps are already being taken at the sewage plants to reduce the amount of phosphorus from the wastewater," Hairston said.

Controlling sediment

Hairston said the level of sediment could be much more problematic than phosphorus levels if the lake continues to be without a management plan.

Efforts are already being made to study and contain stream flow and sediment moving toward Cayuga Lake. The U.S. Geological Survey, in conjunction with the City of Ithaca, is monitoring stream flow and sediment deposits at Six Mile Creek in order to plan for stream bank stabilization, restricting the amount of sediment moving into the reservoir.

Jose Lozano, one of the overseers of the project from the City of Ithaca, said the 4-year-old project will establish preventive measures to control the silt problem.

"We, and the DEC, are concerned about the drinking water, erosion of private property and the threats to wildlife posed by the high levels of silt," he said.

What makes a healthy lake?

Elizabeth Moran, a consultant with EcoLogic, an environmental engineering firm in Cazenovia, has studied the lake since coming to Ithaca in 1977.

"The water quality in Cayuga Lake is very high in an absolute sense, as well as compared to other lakes in its category, especially given everything that the lake is used for, from boating to fishing, sewage dumping to the water supply," she said.

When the public thinks of water quality, Moran said it is important to recognize the elements of a productive lake -- the abundance of algae, plants and other aquatic life forms.

"With ecosystems, everything must be in a balance, so nutrient levels, like phosphorus, algal growth and even dissolved oxygen levels all are part of and support aquatic life and are not necessarily a bad thing," she said.

Since the northern part of the lake is much more agriculturally focused, the pesticide and herbicide levels that are part of the runoff into the lake are of definite concern to people drinking the water.

The U.S. Geological Survey, in cooperation with the DEC, has been monitoring the pesticide and herbicide levels in three major tributaries to the lake and at various sites within the lake.

David Eckhardt of the U.S. Geological Survey said, "With very few exceptions during storm runoff time, the risk of exposure to unsafe levels of pesticides and herbicides throughout the lake is very low."

Global impacts on the lake

Beyond the local runoff and sediment flow, factors beyond Tompkins County are having slow impacts on the lake. Lars O. Hedin, professor of ecology and systematics at Cornell, said gradual climate changes "certainly have an effect on the lake, but not necessarily in predictable ways."

And Hedin said it is very difficult to alter the impacts that industry and society have on climate.

Hedin said the lake is well-buffered by the surrounding hills and not nearly as sensitive to the effects of acid rain as lakes in the Adirondacks.

The cooling questions

Since its introduction to the public five years ago, residents have raised concerns about Cornell's Lake Source Cooling Project and its potential effects on the lake.

Lake Source Cooling is Cornell's $55 million plan proposed in 1994 to cool buildings and equipment on the Cornell campus using water from Cayuga Lake. The system would draw cold water from about 250 feet deep in the lake and run it alongside water pumped down from Cornell in a heat exchange facility near the lake's east shore. There, the lake water would cool the Cornell water, while keeping the liquids separate. The newly chilled water from Cornell would be pumped back up to campus to cool buildings and equipment, while the warmed lake water would circulate back into the lake.

Opponents point to the lake's classification as "impaired" by the DEC and its recent inclusion on a federal list. Under the U.S. Clean Water Act, discharges are prohibited to water bodies on this list if the discharges will make the problems worse.

Walter Hang, president of Toxics Targeting, an Ithaca firm that generates computerized environmental reports, was hired to generate maps of toxic sites around Cayuga Lake by the Cayuga Lake Defense Fund, a citizens group opposed to the cooling plan.

"The lake is extensively impaired by pollution problems that are clearly associated with nutrient problems and silt," Hang said.

Cornell maintains that the project will not harm the lake, nor its residents.

Since water with relatively low phosphorus levels will be discharged into an area with high phosphorus values, this water --which is not a new source of phosphorus because it comes from within the lake -- will actually dilute the phosphorus in the area, said Robert R. Bland, director of Cornell's Environmental Compliance Office.

Bland added that, with all of these concerns, Cornell will continue monitoring, and, if Lake Source Cooling is found to harm the lake in any way, steps will be taken to reverse the problem.

"We appreciate everyone's concern for the lake," Bland said. "And we are concerned, too. There are a number of safeguards going forth."