Lake George Water Quality

Lake George: Class AA-Special water quality, but also impaired


Lake George is rated Class AA-Special by New York State. It is drinking water. Despite this very high classification for the Lake's water quality, Lake George is also on New York's 303(d) list of impaired waterbodies because the Lake and a number of its tributary streams are listed as impaired from silt and sediment caused by stormwater runoff and erosion.

Lake George between Islands

Untreated stormwater runoff is by far the greatest human contributor to water quality decline in Lake George. The stormwater runoff and siltation from stream erosion — and the problems they cause — are from natural and non-natural issues, and solving those problems are one of the main focuses for our project manager and for our partners. The Lake George Association performs many of those projects to solve siltation and stormwater runoff issues every year; you can read about them in our newsletters and on the Lake-Saving Projects page here.

Key factors affecting Lake George water quality

Water quality is a result of what goes in the water (nutrients, pathogens, contaminants, invasive species) and what stays there (increased productivity, turbidity, etc.). When managing Lake George's water quality, key factors we consider include:

You might think that in a large, deep basin of water like Lake George, any pollution entering the Lake will just be diluted. While it's true that the Lake's depth does allow for a certain amount of dilution, Lake George's long retention time means that what does enter is there for a long time. If the rate of pollutants entering the lake increases too quickly, the Lake’s natural capacity to clean itself can’t keep up.


Watersheds and Water Quality

The mountains surrounding Lake George create a small watershed with steep slopes. This small, forested watershed doesn’t produce much pollution; it keeps Lake George’s water clean and clear.

You could compare our watershed with one like Lake Champlain. The much larger Lake Champlain watershed has areas of flat land that allow urbanization and agriculture. Due to its size and land uses, pollution from the Lake Champlain watershed has had a much greater impact on the water quality of that lake.

Map comparing Lake George and Lake Champlain

How human activities in the watershed affect the Lake's water quality

Lake George has had watershed size and land use on its side for a long time. However, add changing land use in the watershed to our Lake's long water retention time, and a decline in water quality is a real concern:

  • When trees and vegetation are cleared for development, the soil (with nothing to hold it in place) quickly erodes, right down the very same steep slopes that have been protecting the Lake for so long.  In addition, stormwater runoff from roads, parking lots, roofs and other impervious surfaces sends pollutants such phosphorus, soil and road salt even more quickly into the Lake.
  • When we bring new and potentially invasive species into the watershed through landscaping, boating, fishing, or other recreational activities, we change the organic matter in the lake.  This changes the water quality and puts stress on native plants fish and wildlife in the Lake George food web.

The health of the lake will continue to decline unless we all do our part to protect the water. We all are here because we love the Lake: the beauty, the tranquility, and the memories it holds for us. But the Lake can’t protect itself. It relies on those who love it to protect it as well.


Runoff diagram