52 THE BEAVER 
preventing floods in the stream below them, holding back a 
surplus of water and permitting it to escape only gradually. 
These dams are of service not only for preventing floods, but 
also for storing water which may be used for irrigation. 
The dam next below the main one is often, if not always, a 
protection to the latter by backing water up against its base, 
enabling it to resist increased pressures from water or ice. 
Of course all the dams of a series may protect one another in 
this manner. 
Another use of beaver dams and ponds to man is that in 
those sections where canoes and light boats are used for 
travel sufficient water is found in the beaver ponds on 
streams where it might otherwise be impossible to proceed. 
Ponds and dams check silt coming down in the stream, and 
prevent it getting into reservoirs, ditches and fields farther 
down. One writer states that stock are now using several 
ranges in the National Forests of Colorado which formerly 
could not be used for lack of water. Beavers made ponds in 
the small streams, conserved the water, and made it avail- 
able to stock during the summer. Beaver dams and flows 
along a stream often prove to be excellent firebreaks, pre- 
venting the spread of forest fires, which are checked by the 
flooded spaces. 
A report of the Supervisor of the Gunnison National For- | 
est, Colorado, gives an example of the value of beaver 
ponds as storage reservoirs. He says: 
“During the protracted drought of the season just passed 
(1924), the water supply for the Minnesota reservoir ran 
low and it was evident that sufficient water for the late 
irrigation run would not be available. Fourteen large 
beaver ponds near the head of Deep Creek and just above 
the Minnesota canal were tapped and the water turned into 
the small stream bed and carried to the company’s canal, 
thence to their reservoir, which was filled by this additional 
