IRRIGATION IN" NORTHERN COLORADO. 51 
difference indicating a loss of 41,000 acre-feet, or approximately 10 
per cent of the supply. In 1917 a demand of 435,000 acre-feet deter- 
mined in a like manner was satisfied with a supply of 414,000 acre- 
feet, the difference indicating a gain of approximately 5 per cent. 
In view of the heavy rainfall of May, 1917, and the very large heads 
carried by all the canals in June and July of that year, it is believed 
that these approximations are in substantial accord with, the facts. 
Conditions in 1916 were nearly normal and for that reason the as- 
sumption may be safely made that the average net loss in the canals 
between the head and the farm lateral is close to 10 per cent of the 
supply. This low figure is probably accounted for by the location 
of the canals one above another with the consequent inflow of seepage 
to counteract a part of the loss. 
These figures indicate that absorption losses account for only a 
small part of the tare for losses charged by some of the common- 
carrier canals of the valley, and that most of it must go to make up 
inequalities of distribution. Under the present system each user 
receives at least his share after the tare has been deducted; but to 
take care of the inequalities of distribution and operation difficulties 
there is practically always a surplus in the canal which must go to 
some one to prevent its waste. It is possible that by spending a few 
thousand dollars for hire of extra riders and reducing the " beat " to 
a distance which will permit 2 or 3 visits every day to all gates and 
weirs to keep them clean and delivering the proper head, at least 
one day's run and perhaps two or three might be added each season 
to each reservoir right. 
SEEPAGE SUPPLIES. 
Practically the entire acreage irrigated in the valley is supplied to 
some extent with seepage water which has been collected in a reser- 
voir or has returned to some channel, but the land dependent on 
seepage as its main supply is limited to the areas shown in Plate XIV. 
FARM IRRIGATION. 
While there are some exceptions, the trend of irrigation practice in 
the valley now is toward a frequent, rapid irrigation, which gives an 
even watering, minimizes percolation losses and end waste, permits 
the use of a large head with a consequent economy of time, and keeps 
the crops growing under moisture conditions with a minimum varia- 
tion from the optimum. 
Only two methods of irrigation are practiced. Alfalfa and grains 
are irrigated by flooding from field laterals. Sugar beets, potatoes, 
