Potential Recovery of Water Chemistry and Stream Biota from Reduced Levels of Acid Deposition at a Sensitive Watershed in the Catskill Mountains, New York

The Catskill Mountains of southeastern New York receive among the highest loads of acid deposition in New York and the northeastern U.S. Additionally, the Catskills are underlain by sandstone and conglomerate, which is base poor and weathers slowly. Thus, the Catskills contain numerous streams with low (< 50 µeq/L) acid-neutralizing capacity (ANC) and are sensitive to impacts from atmospheric acid deposition. Since at least 1983, however, the levels of acidity in atmospheric deposition (primarily sulfuric acid) have been declining in the Catskills and throughout New York. While widespread recovery of streams in the Catskills has not yet been confirmed, recent data suggest that recovery in waters with ANC values in the range of 30 - 70 µeq/L may be starting. This early recovery of stream chemistry may eventually result in the recovery of acid-intolerant biota in affected streams.

The Neversink River in southeastern New York is the most acid-sensitive watershed in the Catskill Mountain region, and among the most acid-sensitive watersheds in the state. Numerous tributaries of this river, and upper reaches of its East and West Branches, have base flow pH values of less than 5.2 and ANC values of less than 0 µeq/L. These acidic conditions and high aluminum concentrations mobilized at low pH have affected fish populations within the Neversink Watershed.

A dataset collected by the New York State Department of Environmental Conservation and U.S. Geological Survey in 1987 indicates that the number of mayfly species in the Neversink River watershed is strongly related to stream pH and ANC values. During the 1987 study, a sharp transition zone was sampled, where the pH of the East Branch Neversink River increased by 0.5 units and mayfly species increased from 1 to 4 within about a 1-km reach. These data suggest that mayfly species diversity may be a good indicator of increases in pH and ANC and of recovery from reduced levels of acid deposition. Data collected by the U.S. Geological Survey since the 1987 study has identified a similar pH transition zone in the West Branch Neversink River. In this study, the sites that were first sampled in 1987 will be resampled to evaluate current stream chemistry and species composition of aquatic macroinvertebrates, fish, and algae. An additional 3-4 stream reaches in the two zones of sharp pH transition will also be sampled.

Objectives - The principal objective of this study is to determine whether the spatial patterns in species composition of aquatic macroinvertebrates, fish, and periphyton have changed as a function of altered spatial patterns in surface-water chemistry since 1987 in the Neversink River upstream of the Claryville stream flow gage. Emphasis will be an examination of the relations of biota with pH, ANC, and aluminum concentrations in light of declines in the acidity of precipitation since 1987. These data will also provide a basis for comparison with future changes in the acidity of precipitation and the acid-base status of surface waters in the Neversink basin.

Results - A paper and report documenting study results were completed in 2006. The paper is in press at the journal, Ecological Indicators, and the report is in press and to be published by NYSERDA. When published, the report will be available for downloading and printing on the USGS New York Water Science Center web site. Figures and tables of data that were developed in this project and are the basis for the paper and report are available at the link below;

Further information on this project can be found at the following link;

Environmental Monitoring, Evaluation, and Protection (EMEP) program at the New York State Energy Research and Development Authority (NYSERDA)

Project Location by County

Ulster County, NY, Sullivan County, NY