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ship channels may alter the ecology and the surface area occupied by 

 the large vessels may well interfere with safe pleasure boating. 



Water transportation is not the only type of transportation consid- 

 eration for estuaries. Since a major percentage of large cities are 

 located on estuarine systems, there is considerable pressure to develop 

 fill areas for airports which then utilize the long overwater approaches 

 to keep the jet noise away from developed areas. The water areas offer 

 a barrier to land travel that must be overcome with causeways or bridge 

 type structures which can interfere with navigation or cause habitat 

 damage. On the other hand, peripheral roads offer some of the more 

 scenic routes available and are frequently the only undeveloped area 

 on which roads can be built. 



Municipal and industrial water supply 



The water in the estuary can serve as a source of both domestic and 

 industrial water supply ; but utilization of estuarine water for domestic 

 supply is very limited at the present time. Normally the brackish water 

 is unpotable and treatment costs to render it potable are extremely 

 high. The brackish estuarine water is also a poor source for industrial 

 process water. Here again a high degree of purity is normally required 

 in the process water and the cost of removing the dissolved salts is 

 prohibitive. 



Estuarine waters are used extensively, however, as a source of in- 

 dustrial cooling water. For this use the most important considerations 

 are the quantity and the ambient temperature. Water temperatures 

 are generally well below the maximum for economical cooling, and 

 since the ocean is connected to one side of the estuary, the quantity is no 

 problem. Cooling water is required by both the manufacturing industry 

 and electric power generation plants ; the greatest use is in the thermal 

 electric plants. 



The distribution of cooling water use parallels population and indus- 

 trial development in the coastal counties, even though electrical power 

 can be transported economically over many miles. The greatest concen- 

 trations of cooling water use are in the middle Atlantic and Pacific 

 southwest regions ; fortunately these regions both have moderate water 

 temperatures which make possible efficient use of the available cooling 

 water. 



There are, however, 47 nuclear powerplants built or scheduled for 

 completion by 1976. All of these are in the megawatt range, with a com- 

 bined capacity of nearly 35,000 megawatts of electrical power. While 

 the bu^k of these will be in the cooler parts of the Nation, 12 will be 

 in the South Atlantic, Gulf, and Caribbean regions where water tem- 

 peratures are high, greater volumes must be used to achieve proper 

 cooling, and the increase in water temperature through the power- 

 plant may be sufficient to cause environmental. damage. 



Waste disposal 



The concentration of population and industrial development in the 

 estuarine zone has led naturally to the use of estuarine waters for re- 

 moval of the waste materials of man's civilization from his immediate 

 vicinity. It is unlikely that cities were built on the coastline with any 

 conscious consideration of the use of the estuarine environment for 

 waste disposal, yet it has happened that this use has become one of the 

 major, uses of estuarine waters and the associated land. Virtually all 



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