Section 4 Fresh Water from Marine Resources 



FINDINGS AND RECOMMENDATIONS 



Alternative fresh water resources that may be 

 available in coastal areas include: 



—Surface water from coastal lakes, estuaries, and 

 up-river reservoirs or lakes with pipelines. 



-Groundwater from onshore aquifers that may 

 extend beneath the sea, offshore aquifers isolated 

 from hydraulic continuity with onshore aquifers, 

 and aquifers containing fresh water "manu- 

 factured" in sediment compaction processes (a 

 hypothesis at present). 



-Desalted water obtained from seawater of high 

 salinity or from brackish surface or groundwater. 



The naturally fresh water from surface and 

 underground sources have been and will continue 

 to be of major importance in supplying coastal 

 areas; they will be only briefly discussed. Desalted 

 water from the sea is growing in importance as an 

 alternative or supplemental source of fresh water 

 in coastal areas faced with shortages of reasonably 

 priced conventional water; it is an important 

 marine resource. Principal attention here is given 

 to desalted water. 



The greatest demand in the near future wiU be 

 for desalting plants of less than 10 million gallons 

 per day capacity. Many of these plants wiU 

 probably be used in special situations; the plant at 

 Guantanamo, Cuba is an example. Desalting tech- 

 nology appears to be advancing at a satisfactory 

 rate to meet whatever requirements may arise in 

 terms of demand for small plants, as well as for 

 larger plants (50-100 mgd) in the future. 



There is a need for continued study of various 

 desalting processes since no one process will be 

 able to fulfill all of the requirements for desalting. 

 A serious question that requires continuing study 

 i&how the Government's research and development 

 effort should be apportioned to the various de- 

 salting processes. More comprehensive data, on 

 potential applications of desalting are needed to 

 improve the Government's desalting development 

 efforts in a realistic manner to meet future 

 desalting requirements in terms of processes, plant 



capacities, occurrence of saline water resources, 

 and the periods of need. 



Little is known concerning the effects on 

 ecology and environment of prolonged discharge 

 of heavy volumes of heated brines into coastal 

 waters. It is probable that some effects will be 

 beneficial and some will be harmful. 



Recommendation : 



A thorough study should be made of possible 

 effects of prolonged release of thermal brines on 

 the ecology and environment as soon as possible 

 after the site is selected and before large-scale 

 plants are buUt. Detailed studies relating to these 

 aspects should continue after a large scale desalting 

 plant is constructed. Ecological and other changes 

 resulting from its operation should be carefully 

 studied and documented. 



Ideas have been developed recently regarding 

 the possibility of subsurface fresh water offshore 

 that may not be directly connected with the 

 present terrestrial hydrologic or gravity system. On 

 the Gulf Coast in Louisiana and Texas, for 

 example, there seems to be both fresh and highly 

 saline water in permeable stratigraphic units 

 occurring under much greater pressure than can be 

 accounted for by the gravity of the circulation 

 system. 



Theoretical considerations suggest that through 

 compaction processes, and later through osmotic 

 membrane phenomena, there may be a separation 

 process in which highly saline water is concen- 

 trated in some permeable sands and relatively fresh 

 water is accumulated in others or in different parts 

 of the same aquifers. These processes, in effect, 

 may be manufacturing "new" fresh water. If so, 

 there may be sizeable sources of fresh water at 

 considerable depth beneath the sea in certain 

 coastal areas that could be extracted for beneficial 

 use. 



Recommendation : 



A definitive program of research should be under- 

 taken to appraise the possibility of water offshore 

 "manufactured" during compactional processes. 

 The critical objectives should be to find out 



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