6 
Bulletin 55. 
A typical stream is shown in Fig. 1. This represents the flow of the 
Cache a la Poudre, on which a longer series of records are available 
than on any other of the Western streams. The diagram is from nearly 
twenty years' record of automatic instruments. 
The stream is low in fall and winter, when the supply is largely 
from springs. It rises in April with the rains or melting snows, 
and more rapidly as the sun and increasing temperature acts on the 
snow fields. 
The rate of rise depends on the area which is covered with snow; 
on the temperature of night and day; on the dryness of the air, as affect¬ 
ing evaporation; the area of the forest! and the character of the snow, 
whether it be new and soft or old and hard. 
DAILY EFFECT OF THE SUN ON THE MELTING. 
A daily rise and fall takes place and is more marked as the river 
rises. This is shown by the various diagrams. Fig. 2 is a fac-simile 
of the diagram taken from the instrument during the week from June 
Figure 2. 
6-13, 1899. The days are shown at the bottom of the diagram, the 
gage depths at the left. “N” indicates the noon hour, “M” midnight. 
The crests of the rises are seen to be twenty-four hours apart. The 
high water occurs from 4 to 6 a. m. at the point where our instrument 
is placed, and the low water about 8 p. m. This hour depends on the dis¬ 
tance to the snow fields. An examination shows that the extreme fluctua¬ 
tion on June 20-21 was nearly a foot, less on the other days. 
When we consider the quantity of water, instead of the depths, 
this fluctuation appears of more importance. Fig. 4 represents the 
quantity of water for the same week as shown in Fig. 2. The scale 
at the left gives the quantities in cubic feet per second. While on the 
evening of June 20 there was less than 3,000 cubic feet per second, 
before morning it had become 4,700 cubic feet, falling back to about 
3,300 cubic feet during the day, and rising again to 3,900 feet during 
the night. This diagram is typical of the fluctuation in sunny weather 
