On the residence time of water in Narragansett Bay

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For Narragansett Bay, Rhode Island, newly calculated and archival data for the area, mean depth, total volume, mean salinity and fresh water input are presented. Estimates of the residence time of the water, derived from 22 sets of monthly mean values, were related to estimates of the fresh water input according to the empirical relationship T=41.8 e-0.00435(FW), where T is the flushing time in days, and FW is the fresh water input in m3 per s; the r2 value is 0.841. Adding estimates of the mean wind speed into a multiple regression increased the correlation coefficient only to 0.864. At the long-term mean rate of fresh water input (105 m3 per s) the flushing time is 26 days. At the lowest mean monthly input rate observed the flushing time was nearly 40 days, while at the highest mean monthly input rate in the data set (325 m3 per s) the flushing time was about 10 days. Known sources of random error appear sufficient to account for most of the deviations from the relationship. The evidence suggests that variation in the flushing time is largely determined by variation in the fresh water input. © 1985 Estuarine Research Federation.

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