The Village of Lake Placid owes much of its picturesque charm to its proximity not to Lake Placid but to Mirror Lake. This small lake's headwaters are located on the slopes of Mt. Whitney and Cobble Hill. Water drains into Echo Lake and then on to Mirror Lake which empties into the Chubb River, a major tributary of the West Branch of the Ausable. Of its 1.2 total square miles, 26% of the Mirror Lake watershed is developed, 19% is surface water, and 55% is forested. A significant portion of downtown Lake Placid sits within the Mirror Lake watershed and Main Street runs along the lake's western shore. This proximity poses significant challenges to maintaining the lake's water quality.
The primary challenges facing Mirror Lake are high levels of chloride and sodium and low oxygen in the deep waters. Mirror Lake has higher levels of chloride and sodium than 97% of the other lakes surveyed as part of the Adirondack Lake Assessment Program. These pollutants enter the lake via the application of road salt to both local and state roads within the watershed. Increasing concentrations of these ions threaten the ability of the lake to support healthy fish populations and other aquatic life. The reduced oxygen in the lake bottom may be a natural phenomenon that is being exacerbated by development, road salt runoff, and climate change.
AsRA and the Adirondack Watershed Institute (AWI) have launched a year-round monitoring program on Mirror Lake. This work has been supported by the Mirror Lake Watershed Association, Town of North Elba, Village of Lake Placid, IRONMAN Foundation, and New York State Department of State. This program will help us better understand the threats facing Mirror Lake and gauge the success of programs to mitigate those threats. We collect vertical profiles of temperature, dissolved oxygen, conductivity, and pH year-round, including through the ice during the winter months. In addition, we collect surface and deep-water samples to be processed by our partner, the Adirondack Watershed Institute. In the spring of 2016 conducted stormwater outfall monitoring to help us better understand where pollutants such as road salt are originating from.
2017 Water Quality Report
This is the second annual report on the limnology and water quality of Mirror Lake issued by the Ausable River Association and the Adirondack Watershed Institute. Our research on Mirror Lake and threats to its water quality continues to yield new insights about the lake. Our goal is to provide stakeholders with the data and science necessary to make informed and effective decisions about how best to protect Mirror Lake. Road salt has emerged as the top threat to the lake, but we have much more work to do before identifying a solution that both protects the lake and provides safe surfaces for people to drive and walk on. This report highlights our most current knowledge of the impacts of road salt to the lake and outlines future work needed to effectively identify solutions.
Key findings include:
- Measures of the lake's trophic status (total phosphorus, nitrate, ammonium, total nitrogen, chlorophyll-a, transparency, and trophic state index) continue to show no significant long-term trends. While many lakes across the state and country are facing threats related to eutrophication, this is not a concern for Mirror Lake at this time. The lake is oligotrophic (low nutrients) and has remained that way over the period of record.
- There is a significant long-term increase in calcium, this may be the result of soil cation exchange as a result of road salt and/or the maintenance of a crushed limestone beach on the lake. Increased calcium poses no specific threat to the water quality of the lake, other than an increased likelihood that zebra mussels could become established in the lake if they were introduced.
- Significant long-term trends in conductivity, sodium, and chloride remain a concern. Elevated bottom water chloride concentrations were documented and evidence exists that these concentrations are impeding the natural turnover of the lake in the spring. The disruption of this important physical process has the potential for a significant negative effect on aquatic life.
- A prolonged period of bottom water hypoxia was documented throughout 2017. This condition is likely natural for Mirror Lake, but it is worsened by the lack of spring turnover. If fall turnover were also not to occur, a die-off of many aquatic organisms – as a result of low dissolved oxygen – would be likely.
- Additional work is necessary to determine the reduction in road salt necessary to protect Mirror Lake and set it on a path of recovery. In order to accurately estimate the reduction in salt necessary to achieve this, we need the entire community within the Mirror Lake watershed to be engaged participants in the study of this problem. The more we know and understand how much salt is applied within the watershed, and where, the better we can understand how much of a reduction is necessary to protect the lake.
The full report can be viewed here.
Older recent reports from the Adirondack Lake Assessment Program and the Citizens Statewide Lake Assessment Program can be downloaded from the sidebar of this page. Monitoring data for Mirror Lake extends back to 1998 and can be found here.