THE IRR IGA TIOX A GE. 425 



To the question as to method, there is choice between two 

 alternatives for an answer. There are two possible sources of water 

 supply. One is underground. The other is in the streams, the water 

 to be taken for each tract or plateau from a point in the stream where 

 the water level is higher than the surface level of the plateau. 



The one means digging deep. The other means carrying irri- 

 gating canals through great distances. 



As to first cost, there is no comparison. The well, on the other 

 hand, must be supplemented with a windmill or steam pumping plant 

 and with an elevated reservoir the size of a well's capacity to irrigate 

 each tract. 



UNDERGROUND FLOW OF WATER. 



Professor Barton of the United States Geological Survey has 

 made extensive investigations as to the underground flow through 

 the arid section and has reported it to be so great and so general as 

 to be practically illimitable as a source of supply of water for 

 irrigation purposes. 



If it were planned to utilize this vast area in Nebraska for agri- 

 culture by perpetually furnishing it water, and all the water it would 

 need, by artificial means, the number of those who scout the idea 

 would be greater even than it is now. But meterologists are of the 

 opinion that, once the soil is made fertile by an artificial water supply 

 and the work of raising crops well under way throughout a consider 

 able portion of the territory in question, nature will go far toward 

 caring for thn water supply then for all time, or so long as the land is 

 kept under cultivation. 



The foundation for the opinion is the theor7 that the plains get 

 no moisture now from the sky, or but little, only because they give 

 none to the sky. The soil in its untilled condition is "peculiarly 

 impervious to moisture, and what rain falls runs into the streams at 

 once and is carried away. None is left soaking in the soil to evap- 

 orate gradually and till the air with mists and clouds and to be 

 precipitated again in rain. 



With the ground, or a large portion of it, under crops, this con- 

 dition would be removed. Whatever rain fell it would be retained in 

 the soil until taken up by the air, as by a great sponge, only to fall 

 again. 



It is not believed tnat by this means the need of irrigation could 

 be done away with entirely for this section. The topography of the 

 region does not warrant such a belief. But it is held that by cultiva- 

 tion the soil could be made partly self-supporting as to its need for 

 moisture, and this would greatly reduce the permanent expense of 

 irrigation. 



Again, it is said that if the ranchmen take advantage of the open- 

 ing offered them under the terms of the reservoir law and build reser- 



