It is obvious that irrigation cannot be practiced without water, and that every ditch which takes water from a stream lessens the volume of that stream below where the ditch is taken out.  It is conceivable that so many ditches might be taken out of the stream, and so much of the water lost by evaporation and seepage into the soil irrigated, that a stream which, uninterfered with, was bank full and even flowing throughout the summer, might, under such changed condition, become absolutely dry on the lower reaches of its course.  And this, in fact, is what has happened with some streams in the West.  Where this is the case, the farmers who live on the lower stretches of the stream, being without water to put on their land, can raise no crops.  Nothing, therefore, is more important to the agriculturists of the West than to preserve full and as nearly equal as possible at all seasons the water supply in their streams.

This water is supplied by the annual rain or snow fall; but in the West chiefly by snow.  It falls deep on the high mountains, and, protected there by the pine forests, accumulates all through the winter, and in spring slowly melts.  The deep layer of half-rotted pine needles, branches, decayed wood and other vegetable matter which forms the forest floor, receives this melting snow and holds much of it for a time, while the surplus runs off over the surface of the ground, and by a thousand tiny rivulets at last reaches some main stream which carries it toward the sea.  In the deep forest, however, the melting of this snow is very gradual, and the water is given forth slowly and gradually to the stream, and does not cause great floods.  Moreover, the large portion of it which is held by the humus, or forest floor, drains off still more gradually and keeps the springs and sources of the brook full all through the summer.

Without protection from the warm spring sun, the snows of the winter might melt in a week and cause tremendous torrents, the whole of the melted snowfall rushing down the stream in a very short time.  Without the humus, or forest floor, to act as a soaked sponge which gradually drains itself, the springs and sources of the brooks would go dry in early summer, and the streams further down toward the cultivated plains would be low and without sufficient water to irrigate all the farms along its course.

It was for the purpose of protecting the farmers of the West by insuring the careful protection of the water supply of all streams that Congress wisely passed the law providing for the establishing of the forest reserves.  It is for the benefit of these farmers and of those others who shall establish themselves along these streams that the Presidents of the United States for the last twelve or fourteen years have been establishing forest reserves and have had expert foresters studying different sections of the western country to learn where the water was most needed and where it could best be had.