the continued preservation of the forest-cover. Uncle Sam is
paying special attention to the western water-sheds which supply
reclamation and irrigation projects. He understands that the
ability of the forest to regulate stream flow is of great
importance. The irrigation farmers also desire a regular flow,
evenly distributed, throughout the growing season.

One of the chief reasons for the establishment of the National
Forest was to preserve the natural conditions favorable to stream
flow. In a treeless country, the rise of the streams is a very
accurate measure of the rainfall. In the region where forests are
frequent, an ordinary rain is scarcely noticed in its effect on
the stream. In a denuded district no natural obstacles impede
the raindrops as they patter to the ground. The surface of the
soil is usually hard. It is baked and dried out by the sun. It is
not in condition to absorb or retain much of the run-off water,
consequently, the rain water finds little to stop it as it swirls
down the slopes. In torrents it rushes down the stream beds, like
sheets of water flowing down the steep roof of a house.

Conditions are very different in a region where forest cover is
abundant. In the forests, the tops of the trees catch much of the
rain that falls. The leaves, twigs, branches and trunks of the
trees also soak up considerable moisture. The amount of rainfall
that directly strikes the ground is relatively small. The upper
layer of the forested ground consists of a network of shrubs, and
dead leaves, branches, and moss. This forest carpet acts like an
enormous sponge. It soaks up the moisture which drops from the
trees during a storm. It can absorb and hold for a time a
rainfall of four or five inches. The water that finally reaches