Hydrodynamic baseline measurements in New Bedford Harbor

Abstract

Thls report includes a compilation of hydrodynamic data obtained in New Bedford Harbor, Massachusetts (Figue 1-1), for the purpose of providing baseline information for the selection of an outfall site for a seondary sewage treatment plant for the city of New Bedford. The observations were conducted by scientists at Woods Hole Oceanographic Institution, commencing in August, 1987 and continuing though March, 1988. They included moored and shipboard measurements of fluid velocity, temperature, salinity, dissolved oxygen and turbidity. The measurement program was designated as the "New Bedford Circulation Study", or NBCS. The study indicates that there are a variety of mechanisms responsible for the transport and exchange of water-masses, of which tidal currents are the most energetic, but wind-driven flows are likely the most effective at renewing the water within the Harbor. Estimates of residence times indicate minimum residence times of less than 2 days during periods of strong winds, and maximum residence times of 4 days or more in periods of weak to moderate south winds. Vertical stratificaton is weak in the winter and moderate in the summer, and it has a notable influence on vertical mixing and on the magnitude of shear currents.