40 ELEMENTARY FORESTRY. 
than six times as great in the open as in the forest. The only 
other conservative effect of forests on water supplies is their 
effect in retarding the melting of the snows. This acts as an 
important function in the prevention ot freshets by giving the 
snow a longer time to melt, so that the snow water has a bet- 
ter chance to sink into the ground. It is of course more evi- 
dent in evergreen than in deciduous forests. On the grounds 
of the Minnesota Experiment Station, where the woodland con- 
sists of a low growth of Oak, the snow is often retained in the 
woods a week longer than in the open. This often allows the 
snow water from the fields to almost wholly run off before it 
has begun to flow from the woods. Then again the daily flow 
of snow water from the woods is much shorter than from the 
open fields during spring weather, when we have warm days 
and cold nights, for it begins later in the morning and stops 
earlier in the afternoon. Under the dense shade and mulch of 
the cedar swamps of northern Minnesota the snow and ice 
often remain until the beginning of summer. The Indians claim 
there has never been a time when they could not find ice for 
their sick in the cedar swamps of that section. This retarding 
effect on the melting of snows in the spring and in preventing 
the run-off is of far greater importance in the case of streams 
that rise in the high mountains than in Minnesota and Wiscon- 
sin, where the land is more nearly level. Where streams have 
their sources in mountains, as those of Colorado and other 
Rocky Mountain States, the cutting away of the forests causes 
a heavy flow of water early in the spring and little water in the 
summer, when it is most needed for irrigation purposes. This 
has become so evident that the Chamber of Commerce of Den- 
ver, Colorado, recently petitioned the President of the United 
States to reserve such land in forests and administer it at public 
expense, and in their petition used in part the following lan- 
guage: 
“The streams upon which the irrigation system of Colorado 
depends are fed by the springs, rivulets and melting snows of 
the mountains, which in turn are nourished and protected by 
the native forests. Where the forests have been destroyed and 
the mountain slopes laid bare most unfavorable conditions pre- 
vail. The springs and the rivulets have disappeared, the winter 
snow melts prematurely, and the flow of the streams, formerly 
