FUTURE NEEDS FOR DEVELOPMENT 251 



rally, so that science cannot say who has been damaged by ar- 

 tificial "rain making." 



The problems of "appropriation" of water vapor in transit 

 are likely to be especially serious to some states. Colorado is 

 a good example. As artificial rain making becomes efficient, 

 it may be possible for the surrounding states to intercept the 

 bulk of the water vapor moving toward Colorado. But that 

 state has natural interceptors of precipitation in its towering 

 mountain ranges, and these already produce stream water for 

 all the neighboring states via the North Platte to Wyoming, 

 the South Platte to Nebraska, the Arkansas to Kansas, the Rio 

 Grande and San Juan to New Mexico and the Colorado to 

 Utah, Arizona, Nevada, and California. If the precipitation 

 is intercepted instead in these other states by artificial means, 

 a question may well arise as to compacts that have specified 

 the rights of adjacent states in water originating in Colorado. 



Soil water seems rarely to have been a matter of controversy, 

 and doubtless the landowner is generally considered to have 

 a rio;ht to it as absolute as to the soil. But if that is the case, 

 the states which have declared "all" water public property and 

 subject to appropriation on a priority basis must hedge. Sci- 

 ence can show conclusively that the ultimate source of prac- 

 tically all water supplies is precipitation, and in any sizable 

 area a significant fraction of that supply has passed through 

 soil somewhere. All appropriators of ground water are con- 

 cerned therefore with what happens in the soil in the area that 

 yields their supplies. 



It is also known that the proportion of precipitation that 

 runs off, infiltrates into the ground, or percolates into ground- 

 water reservoirs can be modified significantly by land use. Full 

 protection of rights to surface or ground water might therefore 

 require supervision of all activities of landowners in the source 

 areas of that water. But if the landowner has only subordinate 

 right to the water that falls as precipitation on his property, 

 the decree of that right should be stated with reference to his 

 operations in the use of his land and protection of the soil 

 against deterioration. 



