Lake George long-term water quality trends
Long-term monitoring of water quality is essential to understand how Lake George has been changing over space and time. Here you can find the results from our analyses of lake chemistry, clarity, and the abundance of floating algae at 14 deepwater sites around the lake for 40 years. There are no data for 2020 because of the research shutdown due to COVID.
This work was funded by the three partners (Rensselaer, IBM, LGA) and the data were recently published in the peer-reviewed journal Limnology and Oceanography.
Water Clarity
The clarity of deep water has not changed over 40 years, as measured by Secchi depth readings. A Secchi depth measurement of 9 meters indicates that Lake George has very high clarity.
Water Temperature
Lake temperature in the top 10 meters of water has increased by 1.3°C (2.5°F) over 40 years.
Salt
Sodium chloride concentrations from road salt applications remain relatively low compared to other lakes around the world, but chloride has increased by 224% and sodium has increased by 222% over 40 years.
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 by 91% over 40 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 7%.
Nitrogen
Nitrogen can also be important in determining algal growth in lakes. As measures of nitrogen abundance, nitrate has declined by 57%, ammonia has declined by 25%, and total nitrogen (measured since 1997) has declined by 13% since first measured in 1997. 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 29% over 40 years, but they remain very low compared to many other lakes in the region. In the fall of 2020 and summer of 2021, Lake George experienced its first two confirmed Harmful Algal Blooms, which are the subject of an intensive analysis by the Jefferson Project to determine their causes.
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. HABs are typically identified by a dense film of floating algae on the surface of the water. Some species of cyanobacteria produce toxins under some conditions. The two Lake George blooms were found to not be producing toxins.