AUBURN — Maine’s lakes and sources of drinking water will need to become much more resilient to combat the dual impacts of climate change and manmade threats.

That was the consensus during the morning session of the annual Androscoggin River Watershed Council conference held Tuesday in Auburn, where experts in environmental fields made a series of presentations on the topic.

Much of it centered on the increasing threats to water quality coming from warmer and wetter weather, which brings more nutrients into lakes, making it much easier for algae to thrive.

Scott Williams from Lake and Watershed Associates told the audience the No. 1 threat to water quality is phosphorus, something that has been at the forefront of talks regarding Lake Auburn.

He said building resiliency in watersheds will mean continuing to implement conservation measures, and focusing on reducing phosphorus loading, preserving wooded buffer areas, engaging the public and more.

“We’re going to have to do something because we’re the problem,” he said.

Holly Ewing, an environmental studies professor at Bates College in Lewiston, has long studied Lake Auburn with the help of her students. She said Tuesday that “the intersection between climate change and land-use change is the biggest threat we have to all our lakes here in the Northeast.”

The combination of reduced ice cover and frequent rainstorms bringing stormwater into the watershed is continuing to test the waiver from filtration that the Auburn Water District holds due to historically clean water.

This spring, Lake Auburn saw the earliest ice-out on record, and on average there are 28 fewer days of ice cover for northern hemisphere lakes.

Ewing said big rainstorms during the winter months — or “rain on snow events” — are also happening more frequently, eroding roads and carrying material into the lake.

“This is the kind of thing we have to worry about now that we didn’t before,” she said.

Williams said heavy downpours in the region increased 74% between 1958 and 2011.

There are certain thresholds the district must continue to meet consistently in order to maintain the waiver. Ewing said, “We want it to stay that way,” but that it “doesn’t always look” like it will be maintained due to algal blooms, low dissolved oxygen that impacts fish, and higher turbidity.

She said more road salt applications during the winter months have also resulted in a “pretty dramatic increase in the salt levels in the lake.”

In recent years, officials in both Auburn and Lewiston have heavily debated the approach to watershed rules and conservation measures, including phosphorus control, septic system standards and development.

Auburn has also placed pressure on the upper watershed towns of Turner, Hebron, Minot and Buckfield to take further measures to control phosphorus runoff.

In the past year, the Lake Auburn Watershed Protection Commission hired a consultant to study where phosphorus is entering the watershed, and recently received a presentation on a “phosphorus reduction analysis.”

According to meeting minutes from March, the consultants are recommending the commission look to reduce the current phosphorus load by 30%, and they made several recommendations on how to accomplish it.

Auburn Water & Sewer Districts Superintendent Mike Broadbent said the consultant recommended remediating “nonpoint sources” of phosphorus, in-lake treatments, dredging the Basin and installing aluminum dosing stations.

Non-point-source pollution refers to a more diffuse source of phosphorus, such as a hillside that’s eroding, rather than a more specific source. Officials have also completed several doses of aluminum sulfate in Lake Auburn, which is designed to break down phosphorus in the water column.

Broadbent said staff are reviewing the recommendations “to develop a plan of action to move forward,” but that no action has been taken yet by LAWPC or the water district.

During the conference, Jeff Stern of the Androscoggin River Watershed Council reviewed several lake protection efforts that are ongoing with the help of grant funding. He said watershed areas can benefit from stormwater management like new culverts and drainage, and efforts to redirect water.

He said one of the best things that can be done for lakes is to leave vegetative buffers intact.

Along with her students, Ewing has been closely monitoring water temperature and oxygen in the lake. She said some years the water temperature is warm all the way to the bottom of the lake, which results in very low or no oxygen in the deepest points.

According to its website, the Androscoggin River Watershed Council’s mission is to improve environmental quality, encourage stewardship, and promote healthy communities in the Androscoggin watershed.

Other sessions Tuesday included the impacts of climate change on outdoor recreation, student work on Lake Auburn and Sabattus Pond, stream quality in the upper watershed and water quality of the Androscoggin River.

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