The Jefferson Project at Lake George Data DashboardYour window into the data driving our science-based approach to protecting Lake George

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 37 years.

This work was funded by the three partners (Rensselaer, IBM, The FUND for Lake George) 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 37 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 1.8°C (3.2°F) over 37 years.


Sodium chloride concentrations from road salt applications remain relatively low compared to other lakes around the world, but chloride has increased by 204% and sodium has increased by 218% over 37 years.


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 70% over 37 years, but it remains relatively low compared to lakes in the region. Total phosphorus, which includes sources of phosphorus bound in the algae, has not changed during this time.


Nitrogen can also be important in determining algal growth in lakes. As measures of nitrogen abundance, nitrate has declined by 54%, ammonia has declined by 36%, and total nitrogen (measured since 1997) has declined by 16% over 37 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.


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 32% over 37 years, but they remain very low compared to many other lakes in the region. Moreover, Lake George has never experienced a Harmful Algal Bloom (HAB).