UNITED STATES DEPARTMENT OF AGRICULTURE 



BULLETIN No. 1110 ^K 



Washington, D. C. PROFESSIONAL PAPER October, 1922 



THE FARMER'S SHORT-BOX MEASURING FLUME/ 



By Carl Rohwer, Irrigation Engineer, 

 Division of Agricultural Engineering, Bureau of Public Roads. 



CONTENTS. 



Page. I Page. 



Description of flume 1 ! Submerged-flow discharge diagrams 9 



Method of calibration 2 i Special tests 12 



Derivation of discharge formulas 5 ' Summary 13 



Free-flow discharge table 6 i 



Many devices have been developed for the measurement of the 

 water delivered to farmers for irrigation, and of these the standard 

 weirs have been most carefully calibrated. When weirs of this type 

 have been correctly designed, installed, and maintained they give 

 accurate results. In some localities, however, especially in the older 

 irrigated sections, types of weirs have come into use that are not 

 standard and that consequently can not give accurate results unless 

 new calibrations are made. For one of the many weirs of this type 

 the following tables and charts have been prepared in order that the 

 structures already installed may be successfully used in the distribu- 

 tion of water. 



The farmer's short-box measuring flume, as shown in Figure 1, 

 is a weir with completely suppressed end coiitractions and a partially 

 suppressed bottom contraction. No provision is made for the aera- 

 tion and lateral expansion of the nappe, as required in the standard 

 weir without end contractions. The floor of the weir box is level, 

 and is placed at the grade of the ditch in which it is installed. The 

 weir bulkhead is variable in height, depending on the conditions it 

 has to fulfill, and it is usually made from the commercial sizes of 

 2-inch lumber. No attempt is made to keep a sharp edge at the 

 crest. As shown in the figure, the bulkhead is not fixed, but may 

 be removed, by sliding it out of the grooves in the walls of the weir 



1 The work upon which this bulletin is based was done with the assistance of M . L. Lightburn and A. B . 

 Crosley under the direction of R. L. ParshaU, senior irrigation engineer, in charge of the irrigation investi- 

 gations in Colorado. The bulletin was prepared in cooperation with the Colorado Agricultural Experi- 

 ment Station. 



3137—22 



