ii8 



KANSAS UNIVERSITY QUARTERLY. 



It is well to note the fact that an inch of water in rainfall is in 

 general not as beneficial as an inch of water applied to the soil by 

 the irrigator, because the rain often falls so rapidly that 50 per cent 

 of it runs off in the drainage channels without soaking into the ground, 

 and secondly the rain does not always come at a time when most 

 needed. If the irrigator has plenty of water, he can apply it to the 

 soil when it will do the most good and withhold it when it is not 

 needed. The number of inches of water required to mature a crop 

 minus the number of inches of rainfall during the irrigating season 

 gives the number of inches of water the irrigator must supply. 



Very few measurements have been made of the evaporation in this 

 region. The following at Dodge City and Colorado Springs were 

 made in ^888 by Mr. T. Russell, of the U. S. Signal Service: 



Dodge City, yearly evaporalion, 54.6 inches: Evaporation for the fotir ii-rigating 

 months, 37.8 inches. Colorado .Springs, yearly evap')ration. 59.4 inche;; evaporation for 

 the 4 irrigating months, 2:^.8 inches. 



The 28 inches evaporated from the surface of water minus the 7 to 

 14 inches of rainfall leaves a resultant evaporation loss from water 

 surfaces during the four irrigating months of from 21 to 14 inches. 

 This water would irrigate an area larger than that of the water surface. 



The temperature and dryness of the winds have much to do with 

 the amount of water required for irrigating, but it is the velocity of 

 the wind in connection with air motors for working pumps to raise 

 water that we wish to consider. The direction of the prevailing wind 

 is also of interest, as some of the wind- mills are constructed on the 

 assumption that this direction is north and south or nearly so. 



Through the kindness of the Chief of the U. S. Weather Bureau I 

 am able to give, in Table II, the average number of hours per month, 

 for the four irrigating months, that the velocity of the wind was o to 5, 

 6 to 10, II to 15, 16 to 20, 21 and upwards miles per hour at Dodge 

 City. These means are for the four years 1889 to 1892 inclusive. 



TABLE II. 



( Max . 



]\Tay. . . < Miu. . 



f Mean 



(Max. 



June.. . - Miu.. 



( Mean 



1 Max. 



July...- Miu.. 



( Mean 



( M.x. 



August", Min. . 



( Mean 



Sum 



L'l an J 

 upwards 



