system. Last year, a marine self-potential profiling unit showed good resuLo 

 in field tests. The instrument operates on the principle that some metallic 

 ore bodies in the sea floor generate electric self-potential which can be de- 

 tected as anomalies in surrounding sea water. 



Mineral deposits themselves are the object of continuing studies at 

 Tiburon where scientists are learning how to model the important char- 

 acteristics and environments of such reserves. Parts of this effort have been 

 moved out to sea, to actual deposits of unusual promise. For example, efforts 

 were directed last year toward modeling blanket-type phosporite deposits 

 off the Pacific coast, using underwater photography, geophysical and geo- 

 logical data, and laboratory analysis of drill samples taken off San Diego, 

 Calif. 



Water Resources 



In 1971, USGS personnel completed a detailed analysis of circulation in 

 Port Royal Sound, S.C.; undertook a joint investigation with the Corps of 

 Engineers, State of Florida, and City of Tampa to determine the potential 

 effects of proposed harbor dredging on subsurface aquifers which provide 

 the city's water supplies; and showed that circulation and flushing of San 

 Francisco Bay are dependent on the inflow of the Sacramento River. Addi- 

 tional continuing effort includes monitoring water discharge and quality in 

 cooperation with all coastal States and research on salt-water intrusion, 

 sediment transport and deposition, relation of streamflow to salinity, changes 

 in dissolved constituents, tidal discharge, and the principles of estuarine 

 hydraulics. 



Such programs are important to the development and maintenance of 

 fresh-water supplies for coastal communities and industry. The need for pro- 

 tecting and enhancing existing supplies has already become a pressing prob- 

 lem in some coastal areas, for example, parts of southern California, 

 southeastern Texas, southern Puerto Rico, and the popular resort areas of 

 southern Florida and the Virgin Islands. If current rates of development 

 are to continue, the need for new sources will become critical. The demand 

 for fresh water in coastal regions over the past 5 years has been increasing 

 by about 10,000 gallons per minute each day. From population trends and 

 water-use practices, it is estimated that the United States will be required to 

 more than double existing fresh- water supplies during the next 15 years. 



With the feasibility of desalting sea water established, the Office of Saline 

 Water conducts and supports research to develop materiads, equipment, 

 and technology for the separation and purification of freshwater from sea 

 water in large quantities at low cost; determine potential environmental 

 effects of operating desalting plants and disposal of waste brines; and 

 evaluate possible mineral recovery from concentrated brines. Developments 

 during the past year have included advances in materials and in corrosion 

 and process controls that may result in substantial cost reductions for 

 future operations. A module-type 3-million-gallon-per-day desalting plant 

 being built in Orange County, Calif., is scheduled for completion in late 

 1972 and will serve as the basic element of a planned 200-million-gallon- 

 per-day plant to meet future critical demands of nearby communities and 

 agricultural areas. 



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