There are three methods in use in supplying water to the arid lands.
The first and the one most generally adopted for obvious reasons is
the gravity system. The waters are impounded in lakes or artificial
reservoirs and carried thence in large main canals, winding about
the hills so as to secure a low uniform grade. Once established,
no other force is needed but the usual flow of the water.
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Another method resorted to when the gravity system is impossible
is to pump the water from the big rivers into smaller reservoirs
leading to the canals, the pumps being kept busy only during the
months in which the water is needed. This method is quite successful,
but requires a somewhat larger annual expenditure. It is being
used in some extensive projects, the water being taken out of the
Columbia river.
The third method is in securing the water by means of artesian
wells. This method is naturally limited to small areas, the projects
being undertaken by individual private owners. Several spots have
been found in the arid belt where this method is successful.