G 
SEEPAGE OK RETURN WATERS FROM IRRIGATION. 
localized gathering area. There may be several on some of the 
channels, so that different seepage ditches may be supplied. 
§ 6. The present measures which are reported, include measure¬ 
ments made on the Cache a la Poudre river and on the South 
Platte, in Colorado. Most of the measurements have been made on 
the former, and have been for the object of determining the amount 
of the increase in the stream; the relation between the increase and 
the amount of water applied; between the increase and the area 
irrigated ; and to collect data which should give the means of study¬ 
ing these facts and other phenomena of the return of the waters. 
The measures on the Platte have been for the same purpose and in 
connection with the office of the State Engineer of Colorado. To a 
greater degree, the measures on the Platte were taken because of the 
light they might show on certain inter-state questions which have, 
or may arise, and on some points that could not be decided from 
the Poudre alone. 
The present and future importance of the inflow was under 
estimated. In the course of the measures, the facts determined 
have led to much wider and more useful application than was 
anticipated during their progress. 
METHODS OF GAGING. 
§ 7. The points at which gagings were made are scattered over 
a distance of 200 miles by the river, without following its meander- 
ings. The distance to be traveled by road is much in excess of this; 
and the distance is made longer for the reason that the highway 
does not follow the river, and at many points the headgates and 
places of gaging are not easily accessible. Some roads cross 
fields and, until an intimate acquaintance is gained with the river 
and the special by-ways, time is lost in passing from one point to 
another. 
The first measurement on the Poudre was usuallv made at the 
gaging station in the Canon, about 12 miles from the College, at the 
point indicated on the map [page IG]. On the way the ditches on one 
side of the river would be examined and the in-takes measured. 
Where the water exceeded more ihan a few inches in depth in the 
smaller channels, or where there was sufficient to measure bv the 
current meter, the meter was used to determine the velocity 
and thus determine the amount entering the canal. In cases where 
the canal was small and the in-take at the time of gaging was lit¬ 
tle, surface floats were often used, and the mean velocitv determined 
in this manner. While not overlv accurate, the results obtained 
can usually be depended upon to within a few per cent., and the 
absolute error where used is too small to make any appreciable 
effect in the general result. 
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