LEWISTON — During the 19th century, the annual “ice out” at Lake Auburn did not typically occur until late April or early May.

Holly Ewing, professor of environmental studies at Bates College in Lewiston, speaks about the health of Lake Auburn water during Thursday’s Great Falls Forum at the Lewiston Public Library. Sun Journal photo by Russ Dillingham

In recent years, that mark — when the lake is clear of ice — has typically occurred in late March or early April, which is one of a complex set of circumstances producing more algae in Lewiston-Auburn’s public drinking water source.

On Thursday, Bates College professor Holly Ewing attempted to unpack the complicated — and now political — issue playing out at Lake Auburn during a Great Falls Forum titled “History and Mysteries at Lake Auburn.”

In the most-basic terms, she told the audience more nutrients, on which algae thrive, are entering the lake through stormwater runoff carrying fertilizer or fecal matter from animals or leaky septic systems.

Added to those factors, she said, are a warmer climate with more annual precipitation. The more the lake is exposed to the sun, the more time there is for algae to grow. More precipitation means more runoff carrying nutrients.

Ewing, who has studied the lake with her students since 2008, focused specifically Thursday on cyanobacteria, also known as blue-green algae, and its origin in the lake. During the discussion, she tied many of the lake’s “mysteries” to the history of the watershed.

The research shared by Ewing is extensive, down to the relative numbers of sheep and cattle present on the farmland near the lake following European settlement. There, she said, were the beginning signs of bacteria entering the lake.

She tracked the parcels of land along the watershed, including those that were used in the past for agricultural purposes and how the land is used now.

Sediment samples from the bottom of Lake Auburn have shown scientists that the soil — gray marine silt and clay left from when the area was below sea level — is naturally rich in phosphorus. She said unfortunately for the watershed, the soil also erodes easily.

Ewing said activities in the watershed “really matter,” and the influence they have on the lake depends on a number of factors, including what is around the lake, what else is in the lake, where in the watershed things happen and the climate.

Recently, the Auburn Water District and Lewiston Water Division have forwarded plans to apply a large dose of aluminum sulfate to the lake this summer, which is designed to eliminate phosphorus.

During questions from the audience, Auburn City Councilor Holly Lasagna said residents should be paying attention to the politics of what is happening at the lake.

Regarding the politics of the situation, Ewing said, “It’s easy to do a treatment of the lake, but it’s much more difficult to control what happens in the watershed.”

Ewing said the state of the watershed makes for a sticky political problem, and one that is playing out in water districts all over the country. She said the largest examples are outside Boston and New York City — two cities that have unfiltered water sources in rural areas far outside the cities. She said those communities are having the same conversations about watershed protection.

The discussion Thursday came the same week Auburn Mayor Jason Levesque announced he would create a committee on water quality, even after the City Council voted not to support it based on lingering questions over the intentions of the committee.

Levesque has said the committee would study the feasibility of building a water filtration plant at the lake, arguing it is a matter of time before the district loses its waiver to deliver the water unfiltered. However, many see the push for a filtration plant as a way to initiate more development or recreation on the lake, which is at odds with water officials’ calls for more watershed protection.

“Once we see a problem in the lake, it’s too late,” Ewing said Thursday. “We’ve missed stuff in the watershed, and we’re starting to see stuff in the lake right now, which means we’ve got problems in the watershed that have not been dealt with.”

She said modeling from other universities suggests there is likely a period of years between when levels of phosphorus or other inputs to the water are added and when they present signs in the lake.

“So what we’re seeing right now in the lake is phosphorus that was added to the watershed perhaps as much as a decade ago,” she said. “That means that as we’re watching phosphorus concentrations in the lake, and we’re saying ‘We’ve got to do something about the watershed,’ we don’t just have to do something, we have to really do something, and we’re going to have to be more extreme than we might have been because we missed something.”

Ewing is an environmental studies professor, teaching courses in soils, water, the landscapes of Maine, community-engaged research and general environmental science.

According to her Great Falls Forum bio, her research projects include investigation of the role of cyanobacteria in lake processes, a study of mercury in stream food webs and development of a smartphone app to enable “citizen scientists” to contribute data about lakes to a central database. Much of her local research has focused on water quality in Lake Auburn.

Ewing said by studying other lakes in the Northeast, she found that important factors in determining the level of nutrients in the water are the size of the watershed relative to the lake and how much of the lake is shallow.

Lake Auburn is relatively small, but its watershed is not. About a quarter of the watershed is in Turner, Ewing said, and it also touches Minot, Hebron and as far north as Buckfield.

Ewing said the Lake Auburn Watershed Protection Commission has authority throughout the watershed, but maintaining relationships with so many municipalities can be difficult.

“It’s complicated and it’s hard,” she said, “and there’s a lot of science underneath it.”

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