murphy: collection and storage of water in KANSAS. 22 1 



City to be a considerable amount greater than that of Salt Lake City. 

 As given in this table the evaporation of Salt Lake is 74.4 inches, and 

 that of Dodge City only 54.6 inches. 



The percolation loss from a reservoir is difficult to measure. It 

 is usually considered in connection with evaporation. As these two 



constitute the total loss, it can be easily found from the differences 

 in depth of the reservoir at any point at two given times. 



The percolation varies from almost nothing in a well constructed 

 reservoir to a large amount in the case of a natural reservoir with 

 sandy or gravelly bottom. Not only alluvium, but rocks also, allow 

 wat^r to pass through them with more or less freedom. The amount 

 which passes varies with the porosity and pressure. Loose sand will 

 absorb from 30 to 35 per cent of its volume, a gravelly sand from 20 

 to 25 per cent, marl from 10 to 20 per cent, clay from 10 to 15 per 

 cent, chalk, sandstone and limestone from 10 to 20 per cent. A 

 formation which is nearly impervious at a low pressure may allow 

 much water to pass under a head of 30 or more feet. 



Not only does the porosity of soil vary a good deal but the varia- 

 tion is often quite sudden. A clay soil in one place will hold the 

 water quite well; in another place, only a short distance from the 

 first, it may be sandy and allow the water to pass through it almost 

 as through a fine sieve. It is impossible to predict from the porosity 

 of the soil in one valley what that in another valley is, even though 

 they be but a short distance apart. A careful examination, not only 

 of the surface formation, but also of the underlying ones is necessary 

 in order to determine approximately what the percolation from a 

 reservoir in a given valley will be. 



Some idea of the percolation through western Kansas soil may be 

 gotten from that from the Perry ditch in Clark county. This ditch 



