204 



DEPARTMENTAL REPORTS. 



MEASUREMENTS OF THE DUTY OF WATER. 



In the arid region suocess in agriculture depends very largely on the 

 control of an ample water supplj^ Where this is assured there is a 

 higher and more uniform prosperity tlian is attained bj^ farmers 

 dependent on rainfall. Experience has shown, however, that fields 

 watered from streams can suffer from drought as well as those which 

 depend on rain. Where the demand is greater than the supply, or 

 where the supplj^ is not properly divided, it often happens that ditches 

 wil be empty at the time when water is most needed. To prevent these 

 disasters there is need of some action to prevent the building of more 

 ditches than streams can fill and secure a just and efficient division 

 of the supply among those in use. To accomplish this those in 

 authority must know how much water is required to ii*rigate an acre 

 of land and how this (luantity varies in different months of the grow- 

 ing season or with different crops. Sooner or later, as has been 

 stated befoi-e, an approximate knowledge of the duty of water is 

 essential to the success of any irrigation system. 



One of the leading purposes of the investigation of this Office is to 

 assist in the determination of the duty of water. The measurements 

 begun last year have been extended this season and are being carried 

 on at the stations and under the direction of the special agents given 

 in the following table: 



Official stations and names of observers. 



STUDY OF LOSSES FROM EVAPORATION AND SEEPAGE. 



The measurement of the losses of water from evaporation and 

 seepage is a part of the general investigation of the duty of water. 

 The quantity of water required to mature croj)s (on a given tract of 

 land) will be less if measured at the place where u.sed than if meas- 

 ured at the head of the ditch or canal which carries it from the 

 stream. The amount lost in transit is an important factor in fixing 

 the general duty of water from a stream and the amount which must 

 be apportioned to each canal to supply the land it irrigates. Last 

 year's measurements showed this loss to average nearly one-third of 

 the total supply. The money value of the water which escapes is 

 very great, amounting in the aggregate to millions of dollars each 

 year. If canals could be so constructed as to prevent this loss, it 

 would add many thousands of acres to the area farmed, and would 



