The Hawaiian gazette., 1904-01-29
THE THEORY AND PRACTICE OF lR
RlGATlON.

The vast arid plains of our Western
States. which but a few years ago
were thought to be unfit for cultivh-
ton, are being rapidly transformed IN
TO fertile fields by the magic of irrl-
cation, The secret of their arid CHAR
acter was found to be the absence OF
moisture, The fertiizing element was
there, but without water to thorough
" mix and knead it with the soil the
rising of vegetable life was retarded or
wholly prevented.
Yet there is no lack OF rainfall in
some of our Western States where
these very conditions obtain. In the
mountains are dense forests which pre-
serve from the suns rays the accumu-
lating rain and discharge it into the
creek and river beds. The plains, being
destitute of trees and other verdure'
offer no resistance to the suns rays,
and the moisture is dried up ana as
sipated almost Immediately
The problem then is to so regulate the
flow and distribution of mountain
streams as to give to the high ana 10"
lands alike an even supply of moisture
when and where needed. In other
words. irrigation turns the desert INTO
a garden, and the swamp into araple
ground. 1t is evident that to accom-
plish a work of such magnitude re-
uuires the highest engineering skill.
The reader must bear in mind that
the lands to be irrigated are frequently
found to be considerably higher than
the adjoining rivers from which Their
supplies must be obtained Thus IRE
ouently it becomes necessary to tap
the stream at a point many miles near
err its source, and to conduct the water
TO the irrigated territory by canal
From this canal, laterals are run
through the sections to be irrigated
and from these laterals still others ana
smaller laterals are extended; Always
however bearing in mind that the mann
laterals must be run in the direction
of the general fall of the land, ana
that only the last or smallest branches
should be at right angles to this ran.
This is for the obvious reason that the
water in the main laterals must nave
a positive flow, while that in the small
est branches Is intended to overflow ana
run down the surface of the gently
sloping ground to the next smaller
lateral below. This, in fact, is the final
process of irrigation. The Western
farmer runs his smallest laterals in
shallow bitches at short intervals
through the field to be irrigated y few
shovelfuls of earth serve to close the
entrances to these bitches until irriga-
ton is needed. At the proper time TINS
earth is removed and the water allowed
to flow into the shallow bitches, and
thence to overflow onto the tributary
ground. AS soon as the soil appears to
have been sufficiently mOistened, the
earth is replaced at the mouth of the
ditch and the flow of water is stopped.
Other more elaborate methods are in
use. requiring sluices dams, and even
artificial lifting of water, but the sim
pie method described will be sufficient
illustration of the principle.
The results of irrigation can best be
seen by a visit to territory where for
few years the system has been III
operation. In regions which few
years since We're but arid wastes, we
now see agricultural prosperity of the
highest order, with the usual accom-
paniment of n prosperous and happy
community. Moreover, we are told that
irrigation gradually changes the entire
floral aspect of the irrigated regions
fowls and reptiles. which We're supposed
to be strangers to the locality, become
acclimated and take up a permanent
abode.
f