Imperial Valley press., 1913-01-09
Drainage Methods

vent, that does the damage.
Drainage Methods
1t would not be worth while for this
convention to listen to a detailed de-
scription of the various methods that
have been developed in this country
for draining irrigated lands, even if the
writer We're a specialist on that sub
iect Those interested Uan obtain far
more information than l can give by
reading the various drainage publica-
lions ISSUED by the Irrigation and
Drainage Investigations OF the United
States department Of agriculture, all Of
which can be obtained free on applca-
ton to the secretary Of agriculture at
Washington. A few general observa-
tions as to methods may, however, be
in place here, especially as they may
did in making clear the results Of spe-
ciflc drainage experiments conducted
by the Irrigation and Drainage Investi-
cations and the state engineer depart
ment Of California near Fresno, to be
taken up later in this paper.
Since the condition that makes drain
age necessary is not due to the water
applied directly in irrigation, but rather
to the water that seeps from canals or
higher over irrigated ground. the fun
damental process in drainage is to in
tercep the excess water in its lateral
ly impervious sub stratum or in its rise
in the form Of ground water. COnSe-
quently the location and depth of drains
is Of prime importance. II it is FEAST
BILE to intercept lateral seepage water
before it reaches a point of injury, it is
obvious that before locating drains the
sub-surface conditions must be looked
into with great care. This simple fac.
is mentioned here because according
to those who have been conducting
drainage investigations it is very fire.
quently overlooked. On the other hand
if the injury comes directly from be-
low, by the rise of ground water, it is
plain that drains must be large enough
carefully laid as to both alignment and
grade, that they will not clog but will
hold the ground water low enough to
give ample feeding room for plant roots
and generally prevent the rise of water
by capillarity and the consequent ac-
cumulation Of alkali on the surface. In
damaged irrigated fields experience has
shown that six feet is about a minimum
depth for tile drains.
Where the adverse conditions Of ex-
cessive moisture has obtained suf-
ficiently long to result in an excess of
alkali it is evident that in addition to
drainage, assuming the natural precipi-
tatiOn is not sufficiently heavy to &C
complish reclamation within a reason
able time, surface flooding is necessary
to wash out the excessive salts. Some
times both drains to intercept lateral
percolation and drains to lower the
ground water coming up from below
are necessary in the same field. Again,
where it is not practicable to place
drains deep enough to collect water
pressing up from below, drainage en-
gineers consider it feasible to excavate
pits four feet or more deep at inter-
walls directly beneath the drains which
when filled with gravel, readily carry
the water up to the level Of the drains.
Occasionally when water seeps laterally
through gravel before reaching and
causing injury to a field, collecting or
"relief" walls in the gravel are sunk
and connected to the drainage system
Where drainage waters can not readily
be. discharged by gravity it has been
found feasible to collect them into
sumps from which they can be pumped
into irrigation canals or other surface
channels lying above the level at w.i1cn
it is desired to maintain the ground
water.
Drainage Experiments In Other States
Since about 1901 the Irrigation and
Drainage Investigations Of the depart
ment Of agriculture have been conduct
ing drainage experiments in the west
ern states, until recently mostly under
the immediate direction Of C. G. Elliott,
who for some years was chief Of drain
age Investigations. Experiments con-
Quoted near Fresno under the direction
Of DR.. Samuel Fortier, chief Of irriga-
ton Investigations. will form later
subject in this paper, but before TAX.
ing them up it may be Of interest to
cite some Of the results obtained else
where. Only brief mention will be
made Of such results as are cited be-
cause the experiments are described
in detail in Farmers Bulletin No. 37i
and in reprint from the annual report