Decades of acidic deposition have adversely affected aquatic and terrestrial ecosystems in acid-sensitive watersheds in parts of the eastern United States. The national Acid Rain Program (Title IV of the 1990 Clean Air Act Amendments - CAAA) helped reduce emissions of sulfur dioxide (SO₂) and nitrogen oxides (NO_x) and resulted in sharp decreases in the acidity of atmospheric deposition. The decrease in acidic deposition produced a steady decline in the acidity of streams in many poorly buffered waters across the western Adirondacks and parts of the Catskill Mountains of New York. Until recently, however, there has been little evidence of biological recovery in most acid-sensitive streams in both regions. Long-term deposition and stream-chemistry records and fish-community data from quantitative surveys done during 1991–93 and again during 2012–19 at 13 sites in the upper Neversink River and its tributaries were evaluated to determine if chemical and biological recovery were evident in this Catskill Mountain watershed and if they could be linked to regional declines in acidic deposition. Between 1991 and 2019, large decreases in sulfate and nitrate deposition in the basin mirrored declines in total nationwide SO₂ and NO_x emissions. There were corresponding decreases in sulfate and nitrate concentrations in deposition at a National Trends Network station at Frost Valley (NY68) and coincident declines in sulfate concentrations at four long-term monitoring sites in the Neversink River watershed. Mean acid neutralizing capacity and pH increased and inorganic aluminum (Al_i) concentrations from routine summertime samples decreased significantly at most moderately to severely acidified sites between the two study periods. Richness, density, and biomass of fish communities increased at most sites, while the density and biomass of brook trout Salvelinus fontinalis populations increased at fewer sites that were undergoing chemical recovery. Although recovery is far from complete, trends in deposition chemistry, water quality, and fish assemblages in streams of the upper Neversink watershed indicate that the 1990 CAAA is having positive impacts on aquatic ecosystems in the Catskill Mountain region, New York.

数十年来的酸性沉积已对美国东部部分地区对酸敏感的流域的水生和陆地生态系统产生了不利影响。国家酸雨计划（1990年《清洁空气法修正案》第IV标题-CAAA）有助于减少二氧化硫（SO ₂）和氮氧化物（NO _x），导致大气沉积的酸度急剧下降。酸性沉积物的减少使整个阿迪朗达克山脉西部和纽约卡茨基尔山脉部分地区缓冲不良的水流中的酸度稳定下降。然而，直到最近，在这两个地区大多数对酸敏感的物流中仍没有生物恢复的证据。1991年至93年以及2012-19年期间在Neversink河上游及其支流的13个站点进行的定量调查得出的长期沉积和河流化学记录以及鱼类群落数据进行了评估，以确定化学和生物恢复是否明显卡茨基尔山流域，如果它们可能与酸性沉积物的区域性下降有关。1991年至2019年，₂和NO _x排放。弗罗斯特谷地国家趋势网络站（NY68）的沉积物中硫酸盐和硝酸盐浓度相应降低，而从没落河流域的四个长期监测点，硫酸盐浓度同时下降。在两个研究期间之间，常规夏季样品的平均酸中和能力和pH值增加，无机铝（Al _i）浓度显着下降，至多为中度至重度酸化。在大多数地方，鱼类群落的丰富度，密度和生物量都有所增加，而河鳟Salvelinus fontinalis的密度和生物量却有所增加在经历化学回收的地点较少的地区，人口增加了。尽管恢复还远远没有完成，但Neversink流域上游的沉积化学，水质和鱼类聚集的趋势表明，1990年的CAAA对纽约州Catskill山区的水生生态系统产生了积极影响。