WATER SUPPLY ON THE GREAT PLAINS. 



BY ROBERT HAY. 



IN a recent issue of THE AGE the editor has 

 indicated that certain statements of Major J. W. 

 Powell, at the Los Angeles Irrigation Congress, were 

 controvertible and would be controverted in the 

 columns of this paper. I, on the contrary, wish to 

 emphasize statements made by Major Powell at the 

 Wichita Convention. So much of the Major's speech 

 at that place was so pertinent to the general question 

 of the water supply of the West that while it ex- 

 presses what I have been telling for several years, 

 yet the authority of the director of the U. S. Geological 

 Survey caused the interest in his sayings to be great, 

 and I wish it to be continuous: Hence this article. 

 While I cannot quote the words used, I will state 

 briefly a few points made by the Major at Wichita: 



1. The rainfall of a drainage area is the sole source 

 of the water supply of that area. 



2. There is no perennial supply of underground 

 water apart from the rainfall. 



3. The rock formations limestone, sandstone, 

 gravel, etc. below the surface are more or less 

 charged with water. 



4. If this water is drawn from the underground 

 rocks by springs, artesian or common wells, the 

 supply will give out unless replenished by rainfall. 



5. After the underground rocks are filled to satur- 

 ation, the rainfall of the region is disposed of in only 

 two ways, viz: By evaporation and by running off 

 towards the sea. 



6. In regions of heavy rainfall (40 inches and up- 

 wards), the runoff is half of the precipitation. In 

 regions of scant precipitation (20 inches and under), the 

 runoff "is diminished to one-tenth of the precipitation. 

 Evaporation disposes, in either case, of all the rest. 



These statements are in the main undeniably true. 

 There is only one that for the region of the great 

 plains needs modification. That modification will 

 appear in what follows. It is important, and I be- 

 lieve that Major Powell from his general knowledge 

 of the region east of the Rocky mountains will allow 

 its value in relation to irrigation. 



If however these statements are true, and to per- 

 sons who have studied the subject almost axiomatic 

 (except No. 6), yet to many people interested in the 

 development of the West they need amplification 

 before they are fully understood. We wish them to 

 be understood, for there is a very practical side to 

 this question of the supply of water for irrigation. It 

 matters comparatively little, if a supply of water is 

 found, whether that water orginally comes from the 

 clouds or from a water factory in the bowels of the 



earth. But while we are seeking water it will save 

 much useless labor and expense if we do not work 

 under a false assumption caused by an incorrect 

 theory. 



MEANING OF RAINFALL. 



By rainfall is meant here, as by most writers, all 

 the moisture precipitated from the atmosphere 

 upon the earth. Precipitation is the better term 

 to use for this totality of rain, snow, hail, sleet and 

 dew. But rainfall properly understood is a handier 

 word and seems less technical, so I shall use it. 



Then the assertion that the rainfall of a drainage 

 area is the source of the water supply of that area is 

 to be fully understood of a particular region only by 

 knowing what the situation is of the watershed of the 

 region, and where is the final outlet of the runoff 

 thereof. The line of a watershed, or "divide," is a 

 very tortuous one. It may follow the rocky ridges of 

 mountain peaks, the highest level of a mountain pass, 

 across the surface of a mountain tarn or marsh, 

 whose waters have an outlet at both ends, or it may 

 be a sinuous trail on a plain that seems perfectly 

 level to the eye. A singe drop of water, if preceded 

 and followed by others, might split itself on a pebble 

 or a pinnacle of rock, and one-half go to one ocean 

 and the other half seek an outlet the whole of a con- 

 tinent apart. The last drops of a rain are mostly 

 reclaimed by the atmosphere through evaporation, 

 and generally all the drops of a short shower are so 

 reclaimed. 



Returning to the fact that the rainfall is the source 

 of the supply of the water for the drainage area it 

 may be well to note a possible exception. That part 

 of the rainfall that soaks into the ground may reach 

 some porous bed that will serve as a storage basin 

 and it will move through the porous bed or beds in 

 the direction of the dip of the strata, to supply any 

 outflow from springs or wells. The dip of the strata 

 does not always conform to the surface topography, so 

 it is possible in such cases that water absorbed by the 

 earth in one drainage area might be discharged by 

 springs or wells in a ravine or plain belonging to 

 another basin. 



DAKOTA'S ARTESIAN WELLS. 



An illustration of such exception is found in some 

 artesian well regions. For example, the best sugges- 

 tion is that the magnificent artesian flow of the wells 

 of the James river region of the two Dakotas have 

 their supply from the rainfall on the highly inclined 

 strata of the Black hills or more distant sources up 



