252 FORESTS, RESERVOIRS, AND STREAM FLOW 
action of the sun’s rays before there is sufficient warmth in the general 
atmosphere to produce any effect. The thinly covered areas melt off 
first and the streams experience a diurnal rise and fall following the 
warmth of day and the frost of night. Nothing like a flood ever arises 
from such melting. 
Under forest cover this action is interfered with more or less, 
depending upon the density of the shade. Even after the ground in 
the open is entirely bare, except under the drifts, the forest areas may 
still be covered with an unbroken layer of snow. It is generally, 
though erroneously, considered that this delay is beneficial, by carrying 
farther into the summer the release of the winter precipitation and 
giving it more time to soak into the ground; but in fact this benefit does 
not result. The water from the first melting of the snow blanket does 
not sink into the ground but into itself. Snow is like a sponge. A 
panful light will shrink to one-fourth of its volume, or less, before any 
free water appears. The author has seen an 8-ft. covering of snow 
dwindle to 2 ft., with the ground beneath it still comparatively dry. 
The forest shade thus holds the snow, which gradually becomes 
saturated from its own melting, until the heat and warm rains of late 
spring or early summer arrive, the soft air everywhere pervading the 
forest depths and finding a maximum exposure of surface to the melt- 
ing influences. A cubic yard of snow which in a great drift might 
stand 27 ft. deep with a square foot of exposure, may here lie with 
a depth of 1 ft. and 27 sq. ft. of exposure. The result is that when the 
final melting begins the whole body of snow disappears very rapidly, 
rushing from every direction into the streams, swelling them to. their 
limit and often causing disastrous freshets. The active melting lasts 
but a short time, and there is little opportunity for the water to soak 
into the ground. The delay in melting, caused by the forest shade, has 
simply operated to concentrate it into a shorter period and increase the 
intensity of the resulting freshet. It comes so fast that the greater 
portion of it cannot be utilized at the time and is lost altogether 
unless intercepted by reservoirs. 
In the open country, on the other hand, the drifts last for weeks 
after the snow has entirely disappeared from the forest, and continue 
to yield a supply of water far into the summer. The period of active 
melting in the open may have lasted four months, that in the forest 
scarcely as many weeks. Fig. 1 illustrates, in a general way, the 
