2 20 KANSAS UNIVERSITY QUARTERLY. 



The places in Table II are chosen so as to show the variation in 

 the monthly rainfall over the state. The first two places are in the 

 eastern part, the next three in the east central, the two following in 

 the west central and the last in the extreme western part. It will be 

 seen that as the mean annual rainfall decreases, the proportion of it 

 falling during the winter decreases. 



Not only the amount of rainfall but the part of it flowing into the 

 streams, or the run-off, must be known before the quantity ofVater 

 a given area will furnish can be computed. This run-off depends on 

 the rainfall area drained, kind and condition of soil, and inclination 

 of surface. It is greatest where the surface is steep and rocky and 

 the rain falls very rapidly. Mr. J. T. Fanning, C. E., estimates the 

 run-off from a flat, cultivated prairie country to be from 45 to 60 per 

 cent of the mean annual rainfall. In some parts of Kansas the soil 

 is very loose and sandy; in other parts the surface is covered with a 

 tough, buffalo grass sod. From the former the surface run-off is very 

 little, not more than 25 per cent; from the latter it is probably at 

 least 60 per cent. 



Evaporation and percolation as here considered are the losses of 

 water from the reservoir, i. e., after collection. The former is the 

 part which passes off into the air; the latter, that which passes off 

 into the ground through the bottom and sides of the reservoir. The 

 former takes place at all times, though most rapidly during the hot, 

 dry summer months; the latter loss is greater when the reservoir is 

 new, and grows less and less as the fine materials in the water fill up 

 the pores of the soil. Evaporation takes place most rapidly when the 

 air is very dry, the water warm and a brisk wind is blowing. These 

 are the conditions existing in western Kansas, and consequently the 

 evaporation is quite great. 



The only recorded measurements of evaporation in Kansas that 

 the writer has seen are those made by Mr. T. Russell, of the United 

 States signal service at Dodge City. They were made with the Piche 

 evaporometer and for one year only. He also measured the evapor- 

 ation at several other places in the west. 



Table III gives the monthly evaporation at eleven places as found 

 by Mr. Russell; also the mean annual rainfall from Ex. Doc. 91, 50th 

 Congress, first session, and the altitudes from Henry Gannett's dic- 

 tionary of altitudes. 



It seems to us that the evaporation at Dodge City as given in this 

 table is too small. Compare for example the evaporation of Dodge 

 City with that of Salt Lake City; the latter is 1800 feet higher and 

 four degrees farther north than the former; the rainfall is about the 

 same for both. We would, therefore, expect the evaporation at Dodge 



