LOSSES FROM CANALS BY SEEPAGE. 
7 
greater. Nevertheless, only on specially favorable days can 
the evaporation from a canal surface amount to as much as 
one-half inch for the twenty-four hours. But the loss from 
seepage is rarely less than one foot and more often twice 
that in the same time, hence the evaporation is relatively 
small and may be left out of consideration in this connec- 
tion without affecting our conclusions. 
CANAL SEEPAGE IN THE CACHE A LA POUDRE VALLEY. 
The Pleasant Valley and Lake Canal is an old canal 
taking water from the south side of the Cache a la Poudre 
river near the canon. It was originally built to supply lands 
in Pleasant valley, a glade of several hundred acres formed 
by the faulting and erosion of the rocks, principally the red 
sandstone, between the Dakota sandstones and the primi- 
tive rocks. The general course of the river is to the south- 
east; the canal sweeps to the south in along curve, mount- 
ing the first and second benches and skirting at places the 
bluffs which form the edge of these benches. The ridge of 
Dakota sandstone confining the river between cliffs on either 
side, forces the canal back to the river, and its course al- 
most overhangs the bed of the river. Through this ridge 
the canal is through and over the rock on a steep grade 
with some tunnels. The bank is often rockwork, with some 
soil. After passing this ridge the canal bends abruptly 
south, leaving the river at a large angle, and skirts the foot 
of the hog-backs formed of the ridge of resisting Dakota 
sandstone. It is thus the highest ditch on the south side of 
the river and like such ditches, is known locally as the 
“Highline.” There is no irrigation of any extent above the 
canal. In several places a few acres are watered from res- 
ervoirs filled from small mountain streams. There can be 
no seepage into the canal except as furnished by the natural 
rains. The drainage of about 35 square miles is cut by the 
canal, but except in or after storms there are no surface 
streams. There are several small streams above the line of 
the ditch, but all disappear before reaching the line of the 
canal. Plum thickets show that spring waters appear 
near the surface in many places. The observers passed on 
foot along the bank of the ditch and thus could not miss 
any of the lateral headgates. 
The conditions were favorable for loss by seepage. 
Much of the soil is of coarse gravel and s^md, and the canal 
skirts the edge of the benches, across sandstone ridges with 
