Monday, April 24, 2017

Mirror Lake Water Quality Report Issued

mirror lakeThe Ausable River Association (AsRA) in partnership with Paul Smith’s College Adirondack Watershed Institute (AWI) have released the Mirror Lake 2016 Water Quality Report. Over the last two years AsRA has worked with AWI to collect baseline information on the lake. They compiled this information, along with historical water quality data dating back to 1971.

Mirror Lake has been enrolled in a variety of water quality monitoring programs over the past 45 years. These range from citizen volunteer water quality monitoring programs to studies conducted by a variety of contractors and researchers. The purpose of this report is to summarize all the available water quality data on Mirror Lake to develop a comprehensive understanding of the current state of the lake.

Report highlights include:

  • There are challenges with comparing historical data to current monitoring efforts due to inconsistency in sampling methodology, frequency, and location over time. Developing a rigorous, methodologically sound, monitoring program is important to understanding future and ongoing changes in the health of Mirror Lake.
  • Measures of the lake’s trophic status (total phosphorus, nitrate, chlorophyll-a, transparency, and trophic state index) do not show significant long-term trends. Earlier reports of increasing total phosphorus may be the result of inconsistency in sampling location.
  • The lake experiences seasonal anoxia (no oxygen) in the bottom waters during the summer stratified period. There is not enough long-term data to assess whether this a natural condition of the lake or the result of urban development in the watershed. This condition, coupled with potentially longer periods of stratification, may pose a long-term threat to the lake trout population.
  • Calcium concentrations are higher today than measurements made in 1971. Current concentrations are within the reported ranged need to support a viable zebra mussel population.
  • There are significant long-term trends of increasing sodium and chloride in the lake. Concentrations are 9- and 11-times higher than the early 1970s, and 52- and 239-times higher than Adirondack lakes not impacted by road salt, respectively. Chloride builds up in the bottom waters of the lake during winter and spring.
  • Stormwater directly entering the lake through outfalls contributes high concentrations of total suspended solids, chloride, and total phosphorus to the lake. High concentrations of all three parameters are found at locations that drain state maintained roads and areas that drain village and town maintained roads and sidewalks.

Click here to view the report.

For more information on the Ausable River Association, visit their website.

Photo: Mirror Lake, courtesy Ausable River Association.

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3 Responses

  1. Paul says:

    So the sampling issues that effected the phosphorus measurements didn’t impact the saline measurements? Are we sure that we knew how much salt was in the water in the past? What is the water source for the lake? Doesn’t water from Mirror lake flow into Lake Placid lake?

    • Paul,

      No, the early chloride measurements were from a different study. As we state in the report, all of the trend analysis need to be approached with some caution due to the variety of sampling techniques used. But, the difference in chloride from 1974 is large enough (4.4 mg/L to 47.8 mg/L) for us to be confident chloride has increased significantly over that time period.

      Regarding the water source to the lake. Water flows in from Echo Lake, but there is also input from storm drains around the lake. As a reference, 34.25% of the land area of the watershed is developed, with most of that concentrated around the lake. You can view maps of this in the report. As you mention in your other comment, we do compare Mirror Lake to other lakes in the region. A study published by the Adirondack Watershed Institute showed that lakes without roads in their watershed had an average chloride concentration of 0.24 mg/L.

      The outlet of Mirror Lake does not flow into Lake Placid, it flows into the Mill Pond which is an impoundment on the Chubb River. The Chubb River is a tributary to the West Branch of the Ausable River.

  2. Paul says:

    The comparison to other lakes is a good way to do it.