Economic Aspects 



The classical sequence — observation, un- 

 derstanding, prediction, and utilization — 

 implies that economic development should 

 be the last stage in knowledge of a region. 

 However, perhaps more often it come first 

 by chance or by empirical methods. Even 

 then we may try to discover the reasons for 

 an economic resource by rationalization. 

 Thus the discovery of future resources or the 

 understanding of present ones must be based 

 on the first three steps of the sequence. Ac- 

 cordingly, it seems desirable to end this study 

 with a discussion of some potential and 

 existing economic resources and their causes. 



Water 



Fresh Water 



Prior to the intensive settlement of south- 

 ern California with its attendant need for 

 large supplies of water, the water table and 

 the pressure surfaces of aquifers sloped sea- 

 ward and fresh water flowed underground 

 to the ocean. Fresh-water springs along the 

 shore and springs rising locally through sea 

 water from shallow depths were known to 

 fishermen and others. By 1905 Mendenhall 

 reported a general shrinkage in extent of 

 artesian area and a lowering of water levels 

 unrelated to deficiencies in precipitation. 

 By 1933 overpumping had reversed the slope 

 of the water table so that in the area north- 



east of Palos Verdes Hills it was more than 

 8 meters below sea level (Eckis, 1934). Pro- 

 gressive lowering continued until the water 

 table fell as much as 30 meters below sea 

 level in some coastal areas. Falling coastal 

 water tables are reported by Upson (\95\b) 

 for Santa Barbara, by Thomas, Marliave, 

 James, and Bean (1954) for the Oxnard- 

 Ventura Plain, by Eckis (1934), Poland, Gar- 

 rett, and Sinnott (1948), Kramsky and 

 others (1952), Baumann and Laverty (1956), 

 and Bookman (1957) for the Los Angeles 

 Plain, and by Poland, Piper, and others 

 (1956) for the Long Beach-Santa Ana Plain. 

 With the reversal of the water table, a re- 

 versal of flow took place, leading to serious 

 contamination of water wells by sea water. 

 The first indication of approaching sea 

 water may be a change in ion ratios, but 

 not the same changes that would be ex- 

 pected of simple mixing of sea water and 

 ground water. Contact with clay minerals 

 may produce alteration of cation ratios in 

 the intruding sea water through base ex- 

 change (Revelle, 1941). Calcium, magnes- 

 ium, and potassium have a far higher base 

 exchange activity than sodium, but, because 

 of the much greater concentration of sodium 

 than of the other cations in sea water and 

 the typical dominance of calcium and 

 magnesium as replaceable bases on the clays 

 that are deposited by streams in the region, 

 the intrusion of sea water usually leads to 



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