Syracuse, N.Y. -- Skaneateles Lake water is so clean the city of Syracuse doesn't need to filter the drinking water it draws from the lake.

But if highly toxic algae blooms like last week's on Skaneateles Lake become more frequent -- as officials and scientists say they will -- the city could be forced to spend millions to build a filter system.

A top state Department of Health official said this week "it's too early to tell" if Syracuse can continue to avoid filtering its drinking water.

"I think in terms of filtration avoidance, you would have to look at all the information available," said Lloyd Wilson, director of water quality initiatives and the Center for Environmental Health. "I think we'd want to understand why that bloom is occurring this year."

Mayor Stephanie Miner said it is "way too premature" to discuss a filter system. "You're piling hypotheticals upon hypotheticals," she said.

Miner said she did not foresee the city needing to build a filtration plant for algae even if blooms became worse in the future. She said the city has contingency plans, including four days worth of storage and the ability to buy water from other agencies, should the algae or their toxins ever reach the city drinking water.

The city of Auburn just spent $600,000 on a powdered-carbon system to filter out blue-green algae toxins, and Auburn pulls about one-tenth as much water from Owasco Lake as Syracuse does from Skaneateles Lake.

Syracuse officials have stressed this week that no blue-green algae toxins have been detected in the city's water because the intake pipes are far from the shore and well below the surface. The city of Auburn's pipes in Owasco Lake, however, are about the same distance and depth, and Auburn has seen blue-green algae toxins in its water.

"We're at the same depth, and (Syracuse's intake) is at the foot of the lake just like ours is," said Sam Granato, a water treatment operator with Auburn. "The town of Owasco's intake is over 60 feet deep, and they got toxins last year."

Granato said Auburn's intake pipes are about 35 feet deep and 1,800 feet from shore. Syracuse's pipes are 24 and 43 feet deep, Wilson said. The Syracuse pipes extend about 2,000 and 4,000 feet from the north shore, according to aerial photographs obtained by Syracuse.com.

Syracuse officials have also said the blooms are near the surface, away from the intake pipes. As Auburn and Owasco reveal, however, the algae can go far below the surface. The algae have tiny air-filled sacs that allow them to move up and down in the water, and strong winds can mix up the water and push the algae and their toxins down deep into the lake.

Syracuse has drawn water from Skaneateles Lake for 123 years, and has a special waiver from the state health department of health to avoid filtering the water. The waiver was granted in part because the landlocked lake has few large boats plying it, and the watershed is small compared to the surface area.

Miner stressed that every water sample taken in the past week, by multiple agencies at multiple locations, has shown that no algae or toxins have entered the city's drinking water.

Skaneateles Lake has been free of the algae blooms that have plagued dozens of lakes around Upstate New York. Until Friday, that is, when a water sample came back positive for the algae. Tests done on Saturday showed that at the north end of the lake, the water had nine times the level considered "high toxins" by the state.

Blue-green algae blooms are caused by high amounts of nutrients running into lakes, generally from farms and septic systems. When the weather gets hot and dry, as it has in the past week, the algae proliferate and produce microcystins, which can kill pets and can cause liver and neurological damage in humans.

This spring's heavy rains, and this month's hot, dry weather, have created the perfect storm for algae blooms. It's the first bloom recorded in Skaneateles Lake since the state's monitoring began in 2012, and the first one long-time residents can ever remember.

It probably won't be the last. Not only are more outbreaks possible this month as the weather remains hot, but once a lake has a large bloom, it's more susceptible to algae blooms in future years.

"Water bodies that have blooms are more likely to have them in the future,"

said Rebecca Gorney, the state Department of Environmental Conservation's program coordinator for harmful algal blooms. "While (the algae) have probably always been there in low numbers, once you have a bloom they remain in the sediments of the lakes, and the blooms can recur when the conditions are right."

As the climate warms and more intense rains fall, the blooms will become more frequent, said Charley Driscoll, an environmental engineering professor at Syracuse University who lives on the lake.

"It's been getting wetter and wetter in Upstate New York for 50 years," Driscoll said, "and as it gets wetter you increase runoff to the lake."

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