36 
SEEPAGE OR RETURN WATERS FROM IRRIGATION. 
of numerous channels has shown that in almost all cases they are dry 
above the lines of the ditches. In some cases waste from irrigation 
and from ditches, not seepage, also reaches these channels. As a rule, 
along the line of the Platte, there is little wasted, especially at the 
time of this measurement. To eliminate the waste, the inflow from 
the same channel was compared in the various years, and in cases 
where unusually large, the excess is counted as waste. The inclusion 
of these lateral inflows causes an increase of the amount by about' 
twenty feet on the average to the mouth of the Poudre. 
RELATION TO AREA IRRIGATED. 
§ 25. If the water returned comes from the water applied in 
irrigation there should be a relation between the amount of water 
applied and the amount returning to the river as seepage. There 
should also be a relation between the area irrigated and the amount 
of return. There are so many interfering conditions, that we can¬ 
not expect to find the relation a very close one, even had we 
the means to know the total area, or the total amount of water 
applied, with accuracy. A portion of the water applied raises the 
water table or the height of the water in the soil. The land newly 
irrigated gives no material return for several years, as most of the 
excess of water applied fills the subsoil. If the land is some dis¬ 
tance from the river the element of time also enters. In the case of 
the Poudre river, there have been many seepage ditches constructed 
for the purpose of taking the seepage water before it reaches the 
river, and again applying it to the land. In the aggregate they use 
a considerable number of second-feet. The increase as shown 
in the tables should be increased by the amount thus used. The 
relation between the seepage and the area irrigated will be obscured 
by these and other causes. The return for any one year is not from 
the water applied in that or in any other one year. It is rather the 
result of the applications of several different years at different dis¬ 
tances. Hence, while the amount varies from year to year, the var¬ 
iation from one year to another is less necessary to take into account 
as the strip irrigated becomes of greater width. In the case of the 
Poudre valley and also in the Platte, the area under irrigation has 
steadily increased since the first measures were made. The total 
amount irrigated in the Poudre valley may be considered as 
between 120,000 and 135,000 acres. The latter sum was used in 
bulletin No. 22, on the “ Duty of Water.” 
Table VI. gives the data regarding the principal ditches in the 
valley, and is given in full to show the character of the land 
devoted to agriculture. In this table, column 3 includes the 
total amount of land supplied with water rights under the canals. 
The waste and pasture land includes much that is not irrigated, and 
some that is. Hence the difference, given in column 11, is really less 
