4 
The: Colorado Experiment Station 
and thereby improves the value of the measurement. 
Divisors are not generally applicable to use on rivers or large 
canals because of the difficulty in operating them. They are prin¬ 
cipally used on the smaller laterals. 
The greater number of them are built to divide the flow in the 
ditch into two ditches, but they are made sometimes as a single 
structure to divide the stream into four parts or more. The divisor 
consists essentially of a flume or box placed in the ditch with one 
or more openings for side ditches and a partition board, or divisor 
board, which may be either fixed or movable. Movable partition 
boards are either hinged, as shown in Figures 1 to 6, or are made 
to move parallel to the side of the flume as shown in Figures 7 
and 8. Provision is usually made for fastening the divisor board 
to a timber across the top of the box when the desired set has been 
made. Fixed divisor boards are used where the division of the 
flow is not often changed, but when a change in the division of the 
water between the two channels is desired, it is usually accom¬ 
plished with this type of divisor by placing boards in a vertical 
position in one or the other of the channels. This method gives 
only approximate accuracy because it reduces the total available 
width of opening in the two channels and also changes the free¬ 
dom of discharge. 
When the proportional division of the flow gives a quantity 
too small for economical use, such as during a shortage of water 
late in the season, or when for any reason the supply is not suffi¬ 
cient to meet the demands of all the irrigators, it is better to give 
each user in turn a greater flow than his share, but for a propor¬ 
tionately shorter time. This amounts to dividing the total water 
available in a period of time rather than a division of the flow at 
a certain time. 
To cover the full range of variations in sizes and methods of 
building boxes, and conditions of flow in the different channels 
would take an endless number of experiments. The tests on 
divisors were, therefore, confined to the forms shown in Figures 
1 to 8, inclusive, and the accompanying tables are based upon the 
results of these 341 tests. In the table headings the word “divisor” 
means the channel or ditch which is taken out from the side of the 
main ditch; “width of divisor opening” is the distance from the 
upstream end of the partition board to the “divisor” side of the 
flume; “channel” is part of the box which carries the remainder 
of the flow of the main ditch; “head” is difference between the 
elevation of the water surface in the main ditch, taken 3 feet up¬ 
stream from the end of the divisor board, and the top of the dam, 
or the floor of the box if no dam was used; and “effective head” 
