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AUSABLE WATER WISE: Science and stewardship on Mirror Lake

Mirror Lake as seen on Monday, March 22 (News photo — Andy Flynn)

By now, it’s not news to Lake Placid residents that high concentrations of salt in Mirror Lake reduce the capacity of the lake to turn over each spring.

For four years — from 2016, when we started intensive monitoring, through 2019 — this essential spring process was halted by heavy salt-laden water collecting in the deepest part of the lake.

In the spring of 2020, after a mild winter, the lake did turn over. Was 2020 an anomaly or a response to less salt use? We don’t know yet, but we do know why it matters. The lack of spring turnover reduces the amount of oxygen in the deep water of the lake, resulting in a cascade of chemical and biological effects. For example, it results in the leaching of phosphorus and metals from the lake sediments into the water column. This can make the lake more susceptible to algal blooms, reduces habitat for native fish to survive, and further threatens aquatic life.

Ausable River Association and Adirondack Watershed Institute staff visited Mirror Lake 26 times during 2020 to test water quality and monitor the lake’s health. To better understand salt inputs, discharge measurements at five continuous monitoring stations established by AsRA, positioned around the lake, were taken 17 times. A monitoring buoy with 18 sensors was installed last year, with funds from the Holderied family and the support of Rensselaer Polytechnic Institute, and is delivering core data. These scientific efforts are part of the multi-year Salt Use Reduction Initiative led by the Ausable River Association.

Why this focus of time and resources? Protecting Mirror Lake is essential to the vitality of the community and to our local and regional economy. It’s a centerpiece — a social space, a recreational resource, and a dazzling complement to the mountains and forest surrounding it. Our focus on rigorous science is one piece of a dedicated project to restore and protect the lake.

The Salt Use Reduction Initiative also brings cutting-edge winter road maintenance technology and expert advisers on industry best practices to the town of North Elba and village of Lake Placid to help them manage, measure and reduce salt applications while maintaining public safety. New “live edge” plows and specialized tracking equipment are mounted on town and village trucks and salt spreaders, thanks to grant funds awarded to AsRA.

And AsRA’s staff is working with the community — residents, visitors, business owners and employees — to reduce salt use, protect the lake, and be part of the solution. The monitoring network, paired with these new technologies and best practices, will pinpoint the reduction in salt usage that triggers a steady reduction in lake salt concentrations. With that information, the community and its leaders, working with state agencies, can make long-term plans that protect the lake.

With spring here, it might be hard to imagine planning for next winter, but that’s what AsRA’s staff and our Salt Use Reduction Initiative partners are doing. There are many ways to help us achieve our goal. If you’d like to support the initiative, protect Mirror Lake, or learn more, contact AsRA’s water quality associate Leanna Thalmann (leanna@ausableriver.org).

(Kelly Tucker is the executive director of the Ausable River Association.)