FUTURE NEEDS FOR DEVELOPMENT 269 



ous kinds of reservoirs that can be used to store these sur- 

 pluses: the soil, ground-water reservoirs, lakes, artificial reser- 

 voirs in headwater areas or along major watercourses. Bal- 

 anced conservation of water resources will depend on all these 

 rather than emphasizing one to the neglect of others. In each 

 locality the methods of storage should be determined on the 

 basis of adequate fundamental data as to natural facilities for 

 storage, and by mature consideration of the social and eco- 

 nomic values to be won by conserving water and other re- 

 sources. 



After a method of storage has been selected, the manage- 

 ment of the water resources developed may be an issue among 

 users because of the various, sometimes conflicting, uses to 

 which the water may be put. In the San Joaquin Valley in 

 California, for example, the question of who shall receive the 

 benefit of artificial storage underground is being argued. Res- 

 ervoirs constructed along streams can hardly serve the needs 

 of all with equal satisfaction. For flood protection they should 

 be empty most of the time, ready to store the surplus water of 

 flood stages and thus prevent damage downstream; but recrea- 

 tional needs are best served if the reservoir is kept full. Mu- 

 nicipal, industrial, and power needs require a fairly steady 

 outflow from the reservoir, while for irrigation the draft on 

 the reservoir is seasonal. For navigation the outflow from the 

 reservoir must continue down the channel, but for irrigation 

 it will be diverted elsewhere. The multiple-purpose reservoir, 

 designed to meet several and sometimes all of these conflicting 

 requirements, may be equivalent to half a dozen reservoirs 

 assembled at a single site. In many instances it is more eco- 

 nomical and effective than single-purpose development, but 

 the conflicting interests may require compromise arrange- 

 ments which do not serve all needs equally well. 



Public Enlightenment 



For most citizens water is only one of the essentials to life, 

 albeit an indispensable one, and they have no more intention 



