Persons familiar with arid
conditions know how quickly the narrow box canyons, which often
drain thousands of square miles, are filled with roaring water after
a comparatively light rainfall.
The run-off
The proper cultivation of the soil diminishes very greatly the loss
due to run-off, but even on such soils the proportion may often be
very great. Farrel observed at one of the Utah stations that during
a torrential rain--2.6 inches in 4 hours--the surface of the summer
fallowed plats was packed so solid that only one fourth inch, or
less than one tenth of the whole amount, soaked into the soil, while
on a neighboring stubble field, which offered greater hindrance to
the run-off, 1-1/2 inches or about 60 per cent were absorbed.
It is not possible under any condition to prevent the run-off
altogether, although it can usually be reduced exceedingly. It is a
common dry-farm custom to plow along the slopes of the farm instead
of plowing up and down them. When this is done, the water which runs
down the slopes is caught by the succession of furrows and in that
way the runoff is diminished.
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