The Environmental Protection Agency’s (EPA) Long Term Monitoring (LTM) network has supported the collection of stream chemistry data in the Catskills since the 1990s. Trends in stream chemistry have periodically been evaluated in these streams but the most recent assessments only extend through the early 2000s. An updated assessment of stream chemistry trends will help evaluate the effects of recent substantial declines in acid deposition during the last decade. This study will evaluate changes in surface water chemistry from 1991 through 2013 at 5 stations in the Neversink and Rondout watersheds in the Catskill Mountains of New York. The results will be compared to changes in atmospheric deposition from three (3) National Atmospheric Deposition Program (NADP) stations in, or in close proximity to, the Catskill Mountains.
Changes measured in deposition and stream chemistry will be compared to those in soil chemistry from 2000 to 2011 at two locations within the Neversink watershed. This work will inform policy by providing important feedback on the success of Title IV of the 1990 Clean Air Act Amendments and other factors that have reduced SO2 and NOX emissions over the past few decades.
Trends in precipitation and stream chemistry will first be evaluated with the Seasonal Kendall trend test (Hirsch and others, 1982), modified from the nonparametric Mann–Kendall test (Mann, 1945; Kendall, 1975). The Seasonal Kendall test identifies monotonic (increasing or decreasing only from the beginning of the dataset to the end) trends in data; it is a robust trend detection method for environmental water chemistry datasets that are often non-normally distributed and contain outliers, missing values, and censored data (Hirsch and others, 1982). The Seasonal Kendall test is a widely accepted form of trend analysis and one that has been used to evaluate data from this region in the past (Burns and others, 2006). The statistical analysis of this updated dataset will be compared to previously published results.
Trends will also be evaluated with the recently developed Weighted Regressions on Time, Discharge, and Season (WRTDS) (Hirsch and others, 2010). The WRTDS method endeavors to describe the magnitude and nature of changes in water quality through time as a function of varying flow and seasonal conditions (Hirsch and others, 2010). By describing the changes in water quality in the Catskill Mountains and comparing that analysis with additional information on changes in precipitation and soil chemistry, we will provide a more detailed analysis of the effects of reductions in acid deposition on Catskill Mountain ecosystems than has been possible in the past. These results will be put into regional context using data from three watersheds in Pennsylvania, the Adirondack Mountains, and New Hampshire/Maine that have comparable precipitation, water quality, and soil chemistry data available.
Watersheds included in the study: the headwaters of Rondout Creek (USGS Site ID 01364959), the headwaters of East Branch Neversink River (USGS Site ID 0143400680), the headwaters of West Branch Neversink River (USGS Site ID 01434021), Biscuit Brook (USGS Site ID 01434025), and the Neversink River (USGS Site ID 01435000).
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“The Forest in Biscuit Brook Watershed”
“Roundout Creek Looking Downstream”