Meade County news., 1918-01-03

(Prepared by the United States Depart
ment of Agriculture.l
Farm reservoirs are rather difficult
to classify for the reason that they are
dependent on number of unlike fac
tors. The materials used, the methods
of construction, locality, cost, source
of water supply, and purpose which
they are intended to serve, all exert
more or less influence. Such being
the governing conditions, any attempt
to present types of such structures
cannot well be made without due con-
sideration of the most influential fac
tors. Thus an earthen reservoir
planned and built to store water for ir-
rigatiOn may be unsuitable to provide
water for stock. Similarly, the mate
rials and methods of construction
by pumping plant may not be well
adapted to a reservoir located in the
bed of stream. Furthermore, a cost
which is justifiable in the citrus or
chards of southern California may be
prohibitive in the Great Plains area.
Reservoirs Considered.
Reservoirs used with pumping plants
will be considered in this article. The
following description is intended to be
typical of a large number of small
earthen reservoirs recently built in
central California to store water fur
nished by small pumping plants and
fhnC a 1OrUa ond affontiua
head for irrigation. The net capacities
of the reservoirs examined ranged from
one-fifth to seven acre-feet and the
average cost per acre-foot of storage
capacity was $97.
The crops irrigated consisted of al
falfa, fruit trees, grapevines, nursery
stock and gardens.
This type of farm reservoir in reality
Is an adjunct to a pumping plant and
the proper relationship between the
two should be studied carefully. The
main purpose of both is to secure at
the lowest rates, water from wells in
sufficient quantities for successful irrl-
cation. This can be done by installing
pumping plant of large enough ca
pacity and dispensing with the reser-
voir. This, however, would be likely
to entail greater first cost for equip
ment, higher annual rate for power,
and a shorter operating time. Where
there Is no reservoir the capacity of
the pumping plant would have to be in
creased at least 60 per cent and since
electric current often is sold at fiat
rate per horsepower based on the
horsepower of the motor, it follows
that pumping plant driven by ten
horsepower motor working ten hours
a day would cost twice as much for
current as a five-horsepower motor
working twenty hours day.
Rectangular in Form.
This type of reservoir usually is rect
angular in form but it may be circular.
The former Is more apt to conform to
fence lines, roads, fields, etc, is more
readily laid out and built, but the lat
ter requires less material and usually
presents better appearance. Before
q site is selected 1t is well to find out
the nature of the subsoil beneath it.
This may be done by boring hole with
an auger or post-hole digger, or by dig
ging a pit to the required depth. If
the examination shows the subsoil to
be porous to considerable depths, the
selection of another site may be advis-
able, but If the porous material is con-
fined to a single stratum it often is
possible to lower the floor of the reser-
volr to a more impervlous foundation
by excavating the upper stratum. Such
course Is followed often for the pur-
pose Of reducing the cost, as the most
economical method Of building an en-
part of the material from within the
site.
The site should be cleared Of all
brush, weeds or other matter subject
to decay, plowed and ridged and
trench dug along the center line. of the
embankment. One of the cheapest and
best methods of pudding the material
placed In the trench as well as that in
the lower and central part Of the en-
bankment, provided the material is
other than clay, is to fill the trench
about two-thirds full of water and
dump good pudding material into it.
The puddled center core should be car
ried up into the embankment for some
distance.
Typical Reservoir.
On a farm near MADEIRA, CAL, there
is reservoir somewhat typical of this
class. 1t is about 21O feet square, the
banks are 7 feet high with slopes of 2
to 1 inside and ~ to 1 out
side, and the top width 3 feet.
The reservoir covers 1 acre of
land and has a capacity Of 4.3
acre-feet. After the banks were
formed by means of four-horse Fresno
scrapers, the bottom of the reservoir
was covered with clay and puddled by
cattle. The water Is raised from q well
by 15-horsepower motor operating a
six-inch centrifugal pump, and dis
charged. into the reservoir through a