Deming graphic. (Deming, N.M.) 1903-1948, 1913-08-01
An irrigation Well

pit can be dug below the water table
depends necessarily upon the posi-
bility of working under water, if Il
pump to drain the pit cannot be used.
and unless the hole is curbed n the
digging proceeds there is great dan
ger of the walls caving in upon the
workmen. Such wells six to ten feet
and over in diameter have been sunk
bv using Il concrete curbng or Il steel
cylinder which lowers or is forced
down rs dirt is removed from within,
but the difficulties attendant upon
such work are enormous and unless
the curbing can be- sunk to ut least
twenty feet below the water table
there is much reason TO expect that
the supply yielded by such n well will
be- very disappointing. The theory OF
this is that the head or pressure
causing the flow into the well i
merely that between the normal level
of the water table and the bottom of
the curbing and if this head i small,
due 10 the impoSsibility of sinking
the well to considerable distance
below the water table. only II limited
supply will enter the well even though
the pit be- large in diameter and the
water be drawn by suction down 10
the bottom. Holes or openings are
sometimes made in the curb which
may increase the flow 10 certain
extent. but increased pumping will
soon draw down the line Of Satura-
ton of the soil, 81 that they will
cease to discharge and the ultimate
capacity will be limited to the amount
which can enter through the area Of
The cross section of the curb at the
bottom under n head equal to the
difference in level between the nor
NAL water table and the bottom of
the curb Consequently this form of
construction l. expensive and the
yield j. never what i expected. II
Is universally agreed that the tube
well and strainer j. the only salts o.
factory method at tapping water
bearing strata and il Is 1T once cheap
and effective. For conditions in which
water j. found at Il depth not greater
than sixty feet from the surface it
j. advisable it i advisable in the ease
of irrigation wells to dig II pit to wa
ter ut least This pit may be lined
with Il curbing of lumber or cement
if it caves badly and il provides a
place for the installation of the pump
short distance above water - that
even though there is considerable
draw down the suction limit of TWEEN
ty-fve feet will not he exceeded. The
tube wells or well may be- sunk in
the bottom of this pit or stump ready
for the draw down to the limit oi
suction or the depth below the water
table at which water will be found
Immediately around the well casing
and strainer while the pump is in OPP
Grafton. The distance through which
the water must be lifted TO get il out
upon the surface is not merely the
depth of the ground water below the
surface, but this distance plus the
draw down. making the actual lift
plus any fractional resistance there
may be in the pump and piping. This
fact should always be kept in mind
when figuring upon the cost of pump
ing. for the less the draw down the
less the head through which water
must be pumped and the cheaper the
pumping. While of course the draw
down cannot exceed twenty five feet
in our altitudc--the suction pump be
ing placed ut the bottom of the open
pitt is always advisable to reduce
the draw down to rs small an amount
as possible by the use of ample
strainers and by placing them in the
most open material available. a
strniner on the end of the well cas-
ing or a perforated easing is of
course necessity and the area Of
the strainer openings in connection
with the suction head or draw-down
will provide a surprisingly large
quantity Of water. There is no ne
cessity in placing the top of strain
err at a greater depth below the nor
NAL water table than twenty-five feet
unless there is bed of gravel at
greater depth in which il is particu-
larly desirable that the strainer be
placed, but on the other hand the top.