160 CLASSIFICATION OP THE PUBLIC LANDS. 



Statutes and court decisions both recognize that water should be 

 devoted to its highest use, and the laws of many States provide for 

 the condemnation of an inferior use in the interest of a higher one. 

 Such laws generally recognize a municipal or domestic use of water 

 as the highest which may be made, because of its necessity in the sup- 

 port of life. Next in order comes the use of water in agriculture for 

 irrigation, whereby the available food supply is affected. The use of 

 water for power, though important and valuable, is inferior to either 

 municipal use or use for irrigation and may, in general, be con- 

 demned if necessary to insure higher utilization. The greatest value 

 of a source of water supply at any particular time will depend, how- 

 ever, on the demands for domestic or municipal use, on the proximity 

 of a tract of arable land adapted to agriculture, and on the quantity 

 of power that may be developed and the availability of a market 

 for it. Such value may change with the development of the country, 

 making necessary the abandonment of established industries in order 

 that the water may be available to supply a greater need. Changes in 

 use will, however, follow the economic law^ as the damage to estab- 

 lished industries must be paid for, and to that extent the cost of the 

 water for other use will be enhanced. 



Important conditions are inherent in the use of water for various 

 purposes. Its use for power affects neither its quality nor its quan- 

 tity, but its use for irrigation depletes its quantity and its municipal 

 or domestic use not only depletes its quantity but impairs its quality. 

 Various uses may be and in many places are compatible with one 

 another. In other places the conflict in use may be only partial. 

 Many of the most advantageous sites for developing power, which, un- 

 der conditions of modern long-distance transmission, are not depend- 

 ent on a near-by power market for their value, are located in the upper 

 portions of river basins, wbere the slopes are steepest and where 

 demands for other use are not likely to be made. Under such condi- 

 tions the water may be utilized in a power plant or a series of power 

 plants and still be available for other purposes by the sacrifice of 

 only so much of the power head as may be necessary to obtain ade- 

 quate pressure in the pipes of the city water mains or to maintain the 

 elevation of canals required to cover irrigable lands. In similar 

 manner water that has been used for a municipal supply may still 

 be available, as sewage, for a certain amount of irrigation. The 

 equalization of the stream flow in order to insure a continuous output 

 of power will in general increase the value of the stream for munici- 

 pal use. The use of water for irrigation, on the other hand, is limited 

 to the growing season and requires the concentration of flow in ac- 

 cordance with the needs of crops during that season. The complete 

 utilization for irrigation of a stream whose flow has been equalized 

 for power will make necessary storage below the power plaixt of the 



