What is an estuary: Physical Viewpoint

The problem of defining an estuary and delineating the area of estuarine oceanography has concerned me since I first started to study these bodies of water fifteen years ago. It is difficult to develop a definition that will include all the bodies of water one wishes to talk about and exclude all others..... From a physical standpoint, the definition of an estuary should recognize certain basic similarities in the distribution of salinity and density, as well as the circulation pattern and the mixing processes; it should point out also the importance of the boundaries which control the distribution of properties and the movement and mixing of waters. This paper continues to discuss the definition of an estuary from the physical viewpoint vs. the biological viewpoint.