JOURNAL OF AGIIim RESEARCH 
DEPARTMENT OF AGRICULTURE 
Vol. V Washington, D. C., November 8, 1915 No. 6 
EXPERIMENTS IN THE USE OF CURRENT METERS IN 
IRRIGATION CANALS 
By S. T. Harding, 
Irrigation Engineer , Office of Public Roads and Rural Engineering 
INTRODUCTION 
Comparisons of the relative accuracy of measurements made in irriga¬ 
tion canals with current meters using different methods are made in the 
following discussion. In connection with field experiments made on the 
flow in various types of canals in order to determine the value of the 
coefficient n of Kutteris formula, 1 detail current-meter gagings were 
necessary. These detail gagings and other observations made at the 
same time have been used to compare the results obtained by the 
standard two-point, single-point, and integration methods, as well as 
by floats and various selected points of measurement. Much experience 
is now available in regard to the various methods of current-meter 
observations used in natural channels. The results given here apply to 
the more regular artificial channels used in irrigation for which there 
are fewer available data. 
In the experiments referred to, the current-meter readings were care¬ 
fully taken at from 12 to 20 points horizontally across the canal section, 
from four to six readings being made at each point. These detail or 
multiple-point observations were plotted, and the mean velocity at the 
different points observed was determined from the vertical velocity 
curves drawn through the plotted observations. The points across the 
canal at which observations were made are referred to in the following 
discussion as the l * verticals.” The results secured by the multiple-point 
reading both in each vertical and for the discharge as a whole have been 
taken as the correct velocities and discharges in the comparisons made. 
In canals of the size used in most of these experiments determinations of 
1 Ganguillet, E., and Kutter, W. R. General Formula for the Uniform Flow of Water in Rivers and 
Other Channels; translated from the German, with . . . additions ... by Rudolph Hering and J. C. 
Trautwine. ed. 2, 240 p., pi. New York, 1893. 
Journal of Agricultural Research, Vol. V, No. 6 
Dept, of Agriculture, Washington, D. C. Nov. 8, 1915 
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