Water Clarity

The clarity of deep water has decreased by about 0.6 m over the past 44 years as measured by Secchi depth.

Water Temperature

Lake temperature in the top 10 meters of water has increased by 2°C (3.8°F) over 44 years.

Salt

Sodium chloride concentrations from road salt applications remain relatively low compared to other lakes around the world. Chloride has increased by 13 mg per liter, but in recent years has begun to stabilize and possibly decline. Sodium has increased slower, only 8 mg per liter higher in 2024 than 1980.

Phosphorus

Phosphorus is a key element that helps determine algal growth in lakes. Orthophosphate is a form of phosphorus that is readily available to be taken up by algae. Orthophosphate has increased slightly over 44 years, but it remains relatively low compared to lakes in the region. Total phosphorus, which includes sources of phosphorus bound in the algae, has increased by less than 1 microgram per liter since 1980.

Nitrogen

Nitrogen can also be important in determining algal growth in lakes. On average total nitrogen is lower now than when first measured in 1997, following the declining trend of two major components (ammonia and nitrate) over the last 44 years. These reductions in nitrogen reflect the reductions in nitrogen oxides being deposited by acid precipitation since clean air legislation was passed in the United States and Canada.

Algae

High concentrations of floating algae can turn lakes green and less attractive for recreation. As a measure of the abundance of floating algae, we measure the concentration of chlorophyll a. Chlorophyll a concentrations in the lake have increased by 0.24 micrograms per liter overall, but they remain very low compared to many other lakes in the region. In the fall of 2020 Lake George experienced its first confirmed algal bloom, with blooms also occurring in 2021, 2022, and 2023. The Jefferson Project is actively researching the causes of these blooms.

A harmful algal bloom (HAB) is a dense concentration of cyanobacteria (also known as blue-green algae) in the water that can be considered harmful due to toxins and aesthetic, economic, or ecological impacts. The NY DEC distinguishes between a Confirmed Bloom, where staff determine based on photos or field reports that there is a cyanobacteria bloom, and a Confirmed with High Toxins Bloom, where criteria meet that of a Confirmed Bloom and toxins are measured above a specific threshold. HABs are typically identified by a dense film of floating algae on the surface of the water. No toxins have been measured in Lake George, and the Jefferson Project reserves the use of “Harmful Algal Bloom” for only those blooms that produce toxins. Blooms with no measured toxins, but that meet quantitative thresholds for chlorophyll will be called “Algal Blooms.”