Current and evolving physical and chemical conditions in the Hudson River Estuary

The physical and chemical environment of the Hudson River Estuary is characterized from data collected during the last 6 decades, with a focus on hydrology (primarily freshwater flow) and water quality (mainly salinity, temperature, and dissolved oxygen [DO]). The most remarkable change during this period is the substantial improvement in dissolved oxygen levels, particularly in the vicinity of New York City and around Albany. A primary reason behind this improvement is wastewater treatment and minimization of point source discharges (raw sewage and industrial effluents). During the summer of 1973, water quality was poor (DO of zero), with no fish life present in the Albany region. It is a given that water quality is but one element affecting biota and ecosystem functions; however, current levels no longer support the septic, polluted label given to the River in times past. The recent DO improvement is one measure of the resiliency of the Hudson River and its recovery from abuse. Also, the last 2 decades experienced greater than average freshwater flows. The data suggest a slight increase in water temperature in certain segments and an apparent, yet to be confirmed, small increase in salinity intrusion for a given flow.