Department of Environmental Conservation

D E C banner

The Adirondack Long Term Monitoring Program

Acid deposition, or acid rain, is an unintended consequence of fossil fuel combustion from vehicles, factories, and electricity generation. By the 1960s, it became clear to scientists that acid deposition was devastating natural resources across New York. The Catskill and Adirondack Mountains were particularly hard hit. Soils were becoming too acidic to maintain healthy forests and animal life, with noticeable tree die-offs at the highest elevations. Many lakes, mountain streams, and some rivers were unable to support healthy populations of fish.

Researchers of the ALTM collecting water samples from an Adirondack Lake
ALTM researchers collecting water samples from
an Adirondack Lake. Photo by Margaret Valis.

Over the years, numerous programs and policies, such as the Federal Clean Air Act and the New York State Acid Deposition Control Act, have reduced emissions of pollutants that acidified clouds, fog, snow, sleet, and rain. Air, water, and biological monitoring networks were established to provide critical scientific data to anchor these policy decisions. One example is the Adirondack Long Term Monitoring (ALTM) Program, which has been documenting changes in the chemistry of lakes, streams, and clouds in the Adirondack Mountains since the 1980s. The ALTM is a collaboration between the NYSDEC, New York State Energy Research Development Authority (NYSERDA), United States Environmental Protection Agency (USEPA), United States Geological Survey (USGS), and Adirondack Lakes Survey Corporation (ALSC). The ALTM chemistry data are available at the ALSC website (see Links Leaving DEC's Website).

More than 20 chemical parameters are measured in each ALTM water sample. These include sulfate (SO4) and nitrate (NO3), which result from the combustion of fossil fuels and have long been associated with acidic rain, snow, fog, and clouds. Others such as acid neutralizing capacity (ANC), pH, and toxic inorganic monomeric aluminum (Al) are important indicators of lake ecosystem health. Research has shown that when fish and other aquatic life are exposed to certain chemical conditions - ANC below 50 microequivalents per liter (µeq/L), pH below 6, and inorganic monomeric Al above 2 micromoles per liter (µmol/L) - they are much less resilient. These conditions are most likely to occur during the spring snowmelt, generally March through April.

Map of ALTM sites that are being monitored.
ALTM monitoring sites
Click to see large image.

Acid-forming air pollution has declined dramatically since the 1980s. As a result, Adirondack lakes and streams are beginning to recover. For example, the acidity level in Brooktrout Lake, thought to be fishless by the mid-1980s, has decreased about 90% since the ALSC began monitoring this lake in 1992. Brooktrout Lake is now able to support self-sustaining brook trout populations. The NYSDEC and its ALTM partners will continue this important program to support key environmental policy efforts even as new stressors, such as climate change, emerge.

Links to these reports are available under Links Leaving DEC's Website. These reports can be found on the NYSERDA website under the section "Ecosystem Response to Atmospheric Deposition of Sulfur, Nitrogen and Mercury".

The Adirondack Long-Term Monitoring Lakes: A Compendium of Site Descriptions, Recent Chemistry and Selected Research Information (Report #11-12)

A Long-Term Monitoring Program for Evaluating Changes in Water Quality in Selected Adirondack Waters (Report #15-24)

Response of Fish Assemblages to Decreasing Acid Deposition in Adirondack Mountain Lakes (Report #17-01)


More about The Adirondack Long Term Monitoring Program: