IV-41 



Even with small tidal ranges and small estuaries, the volumes 

 of water being moved by tidal flow are fantastic. At Charleston, 

 for example, in 6.5 hours 25 billion cubic feet of water move 

 into or out of the harbor in one tidal cycle (IV-1-3). This is 

 more than enough volume of water to supply the entire population 

 of the United States with water for one day. The volume of water 

 flowing into or out of Great South Bay on Long Island in one 

 tidal cycle is adequate in volume to supply the City of New York 

 for one week. 



The combination of tidal action and river flow gives rise to 

 that unique phenomenon called an "estuarine circulation pattern", 

 which usually means that fresh water flows in one direction in 

 one layer and salt water flows in the opposite direction in 

 another layer with various degrees of mixing at the interface 

 between them. This type of circulation pattern is of great impor- 

 tance in some of the estuaries along the Atlantic and Gulf coasts, 

 and to a large extent aoverns the capacity of such estuaries to 

 rid themselves of waste materials. 



