CHAPTER X. 



DUTY AND MEASUREMENT OF WATER. 



In order to determine the amount of land which can 

 be served by the flowing water of an irrigating season 

 and by the storage of water of the non-irrigating season, 

 it is necessary to ascertain the quantity of water which 

 should be used in serving a definite area of land. This 

 is called by irrigation engineers the duty of water, which 

 by the way is affected by the amount of rainfall, the arti- 

 ficially supplied water being complementary to it. It is 

 also affected by latitude, altitude and other climatic con- 

 ditions. It is further affected by the character of the 

 soils, and finally depends largely upon the kind of crops 

 raised. 



In the storage of water in order to determine the 

 amount which can actually be conserved for useful pur- 

 poses, it is necessary to ascertain the extent and the rate 

 of evaporation under different conditions of latitude, 

 altitude and general climate. Local condition, character 

 of the soil, slope of the land, cultivation, humidity, evap- 

 oration, precipitation, drainage, and capillary action 

 are so widely at variance in different localities, that there 

 is small hope of getting any formula which will admit of 

 extended application. Crops differ with respect to mois- 

 ture requirements. For example, oats and wheat will 

 require more than rye and barley, and buckwheat, amber 

 cane and corn still less than the other grains. 



In Colorado, water rights vested on a basis of the low 

 duty assigned to water ten years ago have, in instances, 

 deteriorated lands and reduced their productiveness by a 



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