ell grassed,
would have to be closed to sheep and goats, with their erosive little
feet and habits of grazing in large bands, because all the drainage went
into creeks, streams, and rivers that lower down on the desert were
needed to irrigate vast areas of valuable farming lands.

_The Roosevelt Dam Case_

Take a single case: that of one national forest in Arizona. At the upper
end of this forest--which is a long, narrow tract covering a great
mountain chain--rise two or three streams; on the eastern slope, the Rio
Verde and the Salt River, on the western, the Agua Fria. A hundred miles
below these heads the government is building, at a cost of more than
$4,000,000, the great Roosevelt Dam which will furnish water to irrigate
250,000 acres of the richest of soils around the city of Phoenix in the
Salt River valley. One of the most serious problems in the construction
of the great dams in the West is the question of silt, which is washed
down in the streams and will eventually fill up and render useless these
expensive dams and reservoirs.

Careful studies of silt prove beyond doubt that its primal cause is the
removal of the forest cover, such as underbrush, weeds, and grasses,
along the streams, which allows the rainfall to run off rapidly. The
grazing over these areas by sheep and goats not only exhausts this
forest cover, but from the cutting up of the soil and the loosening
effect of the thousands of tiny hoofs, the erosive action of the rain
becomes disastrous. The wash of the hills and mountain-sides carries
with it into the streams tons and tons of silt to fill up the dams and
beds of the streams, as well as working irreparable injury to the
comparatively thin soil covering the mountains.

On this national forest the watershed on the eastern side all runs into
streams which eventually reach the Roosevelt Dam; on the western slope
the water runs unused to the Gulf of California. So the National
Reclamation Service, charged with the building and maintenance of these
huge reservoirs, said to the Forest Service: "The watershed of the
Roosevelt Dam must be protected from over-grazing, so that the forest
cover may be preserved, and the deposit of silt reduced to the very
lowest possible percentage."

[Illustration: THE SAME HILLSIDE AFTER TWO YEARS OF CAREFUL AND
SYSTEMATIC GRAZING]

The Forest Service whose duty it was under the law to protect and
preserve, not only the timber of the mountains, but the water