DIVISORS 
(For the Measurement of Irrigation Water) 
\ 
u. 
By V. M. CONE, Irrigation Engineer 
S. Office of Public Roads and Rural Engineering 
Many of the canal companies of the West are co-operative 
stock companies in which the individual water users have rights 
to proportional parts of the supply of water furnished by their 
canal, the divisions being in the ratio of the stock owned in the 
canal company. Even a few rivers have their waters divided into 
proportional parts among the canals, regardless of the flow in the 
stream at any time. Under this system it is often considered un¬ 
necessary to have the water actually measured, so long as each 
gets his proportionate part of all the water available in the ditch 
or stream. This led to the use of the divisor, division box, or pro¬ 
portional divisor, which are different names for a device placed 
in a channel for the purpose of dividing the flow into two or more 
parts, as might be desired. 
Divisors are made in many forms and sizes. In all of them 
the division is made in accordance with the cross-sectional area 
of the box, the assumption being that the rate of flow is the same 
in all parts of a section across the box. This assumption is in¬ 
correct to a greater or less degree, depending upon conditions as 
indicated in the tables contained in this bulletin, but they are con¬ 
venient devices because when they have once been set, they will 
give approximately the same division of the flow regardless of 
the later increase or decrease in the main supply. However, they 
are inaccurate and unreliable unless constructed and operated un¬ 
der definite conditions and, therefore, they should not be used as 
measuring devices where any considerable reliability is required. 
Divisors are used extensively in some districts in Colorado 
and Utah, but are not known in others. As early as 1867 a divisor 
patterned somewhat after an Italian device was used near Greeley, 
Colorado, by Hon. J. Max Clark.* The Max Clark box, as it is 
known, is used to both measure and make a fair division of the 
water. Its characteristic feature is an enlargement on the up¬ 
stream side of the box, which reduces the velocity of the water 
““Colorado Station Bulletin 27, p. 8, and U. S. G. S. Water Supply Paper 9, 
P. 70. 
