The Caldwell tribune. [volume] (Caldwell, Idaho Territory [Idaho]) 1883-1928, 1911-03-03

well known fact that water will rise
above its free surface in tubes of
small diameter The force which
causes this action is called capillary
attraction and it is active in the case
of soils, the soil spaces between the
soil particles behaving like tubes
Water will rise above its free surface
in free soil to greater or less height
the height depending upon the char
acter of the soil, and the size, form
and arrangement of its particles and
varying from a few inches to several
feet. The alkaline salts are soluble
in water and in the early history of ir-
rigation of a tract of land are leached
out of the soil and carried downward
to the ground water reservoir, rem
dering the soil free from immediate
danger, but giving false sense of Sc
curity that is often disastrous. The
solution of alkaline salts in naturally
drained soil is concentrated at the
lower limits of the upper saturation,
and at the upper limits of the lower
oabui ohiOh' 40 lh( SlOu "dlOl
level rises, due to over-irrigation,
these limits approach each Their and
eventually merge, whereupcn the CON
centration is found at the upper limit
of saturation. When the ground water
level reaches a point at a depth be-
low the surface equal to the height to
which the water will rise by capillary
attraction, the concentrated solution is
at or near the ground surface and the
general movement of alkaline salts is
continually upward The water is
evaporated from the surface of the
ground, leaving the alkaline salts de-
posted in visible accumulations to
work such damage as they may. If,
however, the excessive irrigation con
tinues, the ground water level will
rise still higher, and more water will
reach the ground surface than the
evaporation can take care of, as re-
suit of which, the surface deposit of
alkaline salts will be taken into solu
ton again and while the total amount
of salts in the surface foot may be
greater than ever, there is an apparent
decrease.
The impossibility of growing crops
in water logged soil and the need
and methods of draining same, are
pretty generally understood, but the
complications arising, due to the pres
ence of alkaline salts, and the necessi-
y for the application of special meth
IDS are not SO we'll recognized. 1t
an not be too strongly impressed
pom the irrigators of the arid west
that drainage is one of their biggest
problems today, and that thorough
knowledge of attendant conditions is
as necessary as a knowledge of the
most efficient methods and soil mani
pulation. AS a matter of fact, the
three subjects are inseparable.
The nature of the soil, in the tract
under consideration, is such that cap
Hilary attraction is effective through
a considerable height, so that deep
drainage will be necessary. 1t is i'm
possible to estimate just how high
water will rise in these soils, but it is
safe to assume that the water level
must be kept at least five feet below
the surface of the ground. It is
highly probable that the cost OF ex-
cavating the drainage canals an ex-
ira foot or so in depth would be more
territory affected Aside from the
territory affected. Aside from the
question of alkali, deep drainage is
necessary for most fruit trees and cs
pecially for alfalfa, the tap root of
which has a strong tendency 10 go
merged.
The nature of the soils has bearing
on the design of the drainage canals
also. The sides slopes must be such
that the banks will stand we'll under
all conditions of weather. The cost
of maintenance of course, will depend
largely upon this, and little care and
attention will repay big returns. The
capacity of the channel must be made
larger than the estimated flow de
| mands, as there are bound to be OBJ
structions presented by spall;np banks
and weed growth. The latter, how
ever, is not of so much Importance rs
in the humid regions on account of the
presence of alkaline efhorencence
along the banks. which prevents Wig
orous growth
It is necessary to design the drain,
age system so that the maximum seep.
age discharge will be amply provided
for. No account should be taken oI
| the stnrape possibilities of the soil