ABSTRACT
The residence time of an estuary, for the moment loosely defined as the average time a waterparcel spends in the estuarine system, is a useful concept for purposes in which only global information about the physical transport processes in an estuary is at hand. For instance, in principle a simple salinity survey of the system, together with knowledge of the freshwater discharge rate, suffices for a first determination of such a time scale. Yet care should be taken that in applying a time scale to a specific process, the application is not at odds with either the definition of the scale or with the assumption on which the scale is derived. Many different scales can be defined, some of which may have the same order of magnitude, but others may differ appreciably.
