The Brownsville daily herald. [volume] (Brownsville, Tex.) 1897-1910, 1908-09-12
Preparation Of Land
For Irrigation
By w. L. Rockwell, Irrigation Man
ager u. S. Dept. Of Agriculture
CONTINUED from Yesterday
Border Method.

For the growing of sowed crops, if
the slope is very uniform and not
over fifteen hundredths of a foot per
hundred feet in silt or clay soil, nor
over three-tenths foot per hundred
feet in sandy soil, and only in one di-
rection, the border method may be
used to advantage. A field may lie
so that the borders may be laid out,
not in the direction of the greatest
slope, but diagonally to it, giving
them the proper slope to fit the soil.
If this is done it will be necessary to
level the ground transversely be-
tween borders. ithout exception,
when this method is used, the ground
transversely between the borders, if
it is not already so, should be made
level, that the water flow in an even
sheet down the whole length of the
border There must be no rising
slope or change of slope at any point
In irrigating by this mthod, you
have no control over the water ex-
cepting as you are able to regulate
the velocity of flow by the head used,
and this too must be controlled by
the character of the soil irrigated 1t
is always desirable, in irrigating or
binary or large fields to have the Dor
ders as long as possible, so long as
thorough irrigation and an economi-
cal use of water and time is had.
Four inches in depth, or four acre
inches is sufficient water for a
thorough irrigation, and the time re-
quired to put such an amount into
any particular soil can be easily de-
termined by experiment. The rate
of flow across a piece of ground with
certain available heads can also be
found. Knowing the amount of wat
er we wish to put into the soil, and
the rate of flow, we can calculate the
length the border should be.
Flooding.
From tests made of the rate of
seepage through the sand and silly
clay soils of the Rio Grande valley it
has been found that from thirty to f1f-
ty minutes is sufficient time for these
soils to absorb four acre inches OF
water. hence in laying out land for
border irrigation in the Lower Rio
Grande valley l suggest the follow
ing: When the soil is sandy and
porous place the borders one hundred
feet apart and make them four hun
dred and forty feet long or then to
the one-fourth mile. Eight cubic
feet of water per second will cover
such bed four inches deep in thirty
minutes. Where the soil is silly
clay place the borders seventy-five
feet apart and make them four hun
bred and forty feet long, AMI four
cubic feet OF water per second will
cover this bed four inches deep in
forty-five minutes. 1t may be ne
cessary to vary these times of flow
according to the irrigation head
available and the texture of the soil,
but 1 believe the idea is the correct
one, to so lay out the border and reg
ulate the head of water used that the
flow applied will reach the length of
border in the time required for the
proper irrigation of the particular
soil, then cutting off the flow from
the supply ditch, the water viii con-
tinue to flow down the border, the
latest water turned on reaching the
lower portion of the border in the
proper time to complete the irriga-
ton. Provision should be made for
any excess water that may reacu the
lower end fthe border to drain in
to the irrigation ditch below. If in
certain instances this is not practical,
a drain ditch should be made to carry
off the excess.
Ito be Continued)