Salinity in the Vellar estuary, southern India. Top figures show the situation at high water, bottom figures at low water. Notice that isohalines are not evenly spaced.
The observation period was preceeded by heavy rain. On 20 January the estuary displays the structure of a salt wedge with a mixing region of about 1 km width. During low tide the freshwater pushes the salt wedge back beyond the observation point; water with high salinity is then found only in some depressions. The freshwater supply decreases significantly as time goes on, and the estuary changes from a salt wedge to a highly and eventually slightly stratified situation (Figure 13.5). The lower layer is then no longer pushed back from the observation point at low tide but its vertical extent is reduced.
Adapted from Dyer and Ramamoorthy (1969).contact address: