IRRIGATION IN NORTHERN COLORADO. 49 
and depend on the judgment of the rider to make a fair division. No 
man's judgment is infallible, and it is to be expected that considerable 
errors must result. Even where weirs are used the installation is 
often faulty enough to produce a difference of 25 per cent between 
the amount supposed to be delivered and the amount actually de- 
livered. In addition the kinds of crops grown no doubt account for 
some of the variation. Because of high prices and war needs the 
acreage of potatoes under 2 or 3 laterals in 1917 was increased at a. 
much greater rate than for the entire canal. This resulted in a 
proportionately lower duty for the lateral. Under other laterals the 
switch was from alfalfa to wheat, and in these cases the duty 
was corresponding^ higher. 
ABSORPTION LOSSES IN CANALS. 
Conditions are such in the Cache la Poudre Valley that there are 
few canals in which sections suitable for measuring absorption 
losses may be found. The quantities to be determined are small and 
the methods of measurement have their limitations, so conditions 
are best when the loss may be determined for a uniform head for a 
long period over a stretch of canal into which there is no drainage 
and from which there is no outflow. Almost without exception, dis- 
tributing canals could not be used on acco'unt of the many diversions, 
beginning almost at the h'eadgate. Canals carrying water for storage 
were usually unsatisfactory on account of fluctuating heads, uncer- 
tain supply, or ice conditions. However, fairly satisfactory meas- 
urements were obtained on the Poudre Valley, North Poudre, and 
Larimer and Weld Canals. 
The measurement on the Poudre Valley Canal was made in the 
latter part of May, 1917, and included a section of the canal from 
the head to a station a short distance above the Dry Creek crossing, 
a distance of 10.6 miles. For the 36-hour period observed, the aver- 
age flow at the upper station was 232.4 second-feet and at the lower 
station 220.0 second-feet, giving a total loss of 12.4 second-feet. This 
is equivalent to 1.17 second-feet per mile or 0.5 per cent of the total 
flow. Expressed in different terms, the loss per day per square foot 
of wetted area was 0.41 cubic foot. 
The measurement of the North Poudre Canal was made from July 
6 to 9, 1916, and covered a period of 58 hours. The section in- 
cluded extended from the rating station at the head of the canal 
to a station near Waverly, a distance of approximately 16 miles. 
During the observation there was a small inflow from Reservoir 
No. 15 and from a small spring a mile above the mouth of Camp- 
74464°— 22 4 
