PART I 



Estuaries 



The river water entering an estuary mixes with salt water and 

 continues its movement to the sea. When the temperature of the 

 river water does not fall below that of the sea water, a net seaward 

 movement of mixed water occurs in the upper layers of the estuary. 

 When the volume of river water received by the estuary in a tidal 

 cycle is constant over a period of time, the volume of river water 

 reaching the sea becomes equal to that received from the land in a 

 tidal cycle. 



Over a period of time the salinity at a point in the estuary will 

 remain practically constant. Since salt is constantly being lost from 

 the upper levels of the estuary, because of the net seaward volume 

 transport from these levels, there must be a net volume transport 

 of salt into the lower levels of the estuary to balance this loss. The 

 situation just described is illustrated in Figure 1. 



From the standpoint of the net volume transport pattern of Figure 1, 

 an estuary can be divided into two volume sections, A and B, as in 

 Figure 1. Here the net flow in A is toward the sea, while the net flow 



RIVER 



ESTUARY 



SEA 



Qa=R + Qe 



MIXED SEA AND RIVER WATER 





FIGURE 



CROSS SECTION OF PIEDMONT- TYPE ESTUARY SHOW- 

 ING NET CIRCULATION PATTERN 



