40 
SEEPAGE OR RETURN WATERS FROM IRRIGATION. 
this might explain some of the exceptional gains. But still better 
is the amount of water which is applied, if it can be known. A man¬ 
uscript map was prepared, showing the location of the water rights in 
the principal canals. A water right usually includes the right to 
the water for 80 acres. From this map a table was prepared, show¬ 
ing the number of rights draining into the river between the dif¬ 
ferent points of measurement. From the amount of water used by 
the different ditches during the year, as shown in Table VI., this could 
be expressed in acre-feet of water, or in the number of acres •which 
would be covered by the water one foot in depth. The inflow can 
not be expected to be very closely proportional to the area irrigated 
or the amount of water applied between these points, or not until 
after a series of years. The return is slow, and there is reason 
to think that the seepage from some of the outer ditches has 
not yet reached the river. The construction of seepage ditches, to 
drain the seepage water from the water-logged land, or to catch the 
seepage water, also interferes with the normal distribution. They 
collect and carry the water sometimes a number of miles from 
where it appears. The effect of the seepage ditches is to increase 
the apparent return near the lower end of the stream. The 
amount of water lost from the canals is much more than from an 
equal area of irrigated land. An area of one acre forming part of 
a canal channel loses as much water as 200 to 400 acres of land 
under ordinary irrigation. The losses near the heads of the canals, 
especially those near the mountains, is greater than the average. 
An estimate of the number of acres of canals would be desirable 
before the study can be completely satisfactory. 
From Table VI., we find 260,000 acre-feet of water is applied 
to 106,000 acres. This includes loss and waste from the canals, and 
is equivalent to a depth of 2.45 feet over the entire area irrigated. 
If this depth were applied by the smaller canals too, we have 284,- 
000 acre-feet applied in the whole valley. 
As a rule, the smaller canals have earlier appropriations from 
the river ; and therefore use water more freely ; hence it is safe to 
assume that at least 284,000 acre-feet of water have been applied to 
the irrigated area. The amount of water which is applied is affected 
by the stage of water in the river. When the river is high the 
canals are full, water is unstinted. If low, the amount used is 
decreased. In this case the ditches of later construction are the 
first to suffer. The development of storage reservoirs has increased 
the amount applied late in the season, especially since 1892. At 
present the reservoirs already in use in the valley of the Cache a la 
Pond re have a storage capacity of about 48,000 acre-feet. Of the 284,- 
000 acre-feet applied to the whole valley, about 35,000 acre-feet is 
applied so that it drains into the channels running into the Platte. 
Deducting this, as it does not affect the inflow into the Poudre, we 
