STORAGE RESERVOIRS. 121 



to be stored for irrigation, as hereafter explained, in order that the water of the arid 

 region may be fully utilized. It must be understood that such a result can be predicted 

 only from a system of reservoirs. The effect of any single reservoir would certainly 

 be insignificant, but the combined influence of many might be very important. 



"Passing now to the question whether the benefits to the lower river from such 

 a system would be of sufficient importance to justify the construction of reservoirs 

 solely for the purpose of securing them, the answer must be distinctly in the negative. 

 It is still true in this case, as in those already considered, that the benefit is not worth 

 the cost. If, however, there are other and primary considerations, which of themselves 

 would justify the construction of reservoirs, then their influence upon the floods of the 

 lower river is a matter worthy of consideration. And when such primary interests 

 are of a magnitude which looks to a comprehensive system throughout the watershed 

 of the stream, subserving interests of a public as well as a private nature, then the argu- 

 ment for Government assistance in such works stands upon a substantial basis. The 

 point to be especially considered, in connection with such a reservoir system, is that 

 river regulation must always be a secondary motive and more immediate and direct 

 uses the primary motive." 



