II-3 



Yet, the dominating environmental factors listed above form a set 

 of natural guiding principles which govern the general characteristics 

 of the estuarine zone of the United States, and the occurrence of 

 various combinations of these environmental factors permits the 

 grouping of the national estuarine system into 10 geographical zones, 

 each governed by a different combination of environmental conditions 

 (Figure IV. 1.19). 



