The Oakley herald. [volume] (Oakley, Idaho) 1908-1961, 1912-04-26
Duty and Measurement
Xxx Of Water Xxx
BY DON n. BARK, U. S. Engineer,
in Charge Of irrigation Investi-
cations in Idaho.
Oregon Short Line Railroad Dem
onstration Train Lecture.


onstration Train Lecture.
The greater part of the land in the
west would be practically worthless
without water with which to irrigate
1t, yet there is far less attention
given to the measurement of this
water than there is TO the measure
ment of the land. Under the Carey
Act the land is sold to the settler
for so cents per acre and would
hardly be worth that without the
water, while water costs the settler
all the way from $25 to 500 per
acre.
Miners Inch.
Water was first used in Idaho and
other western states for mining pur-
poses, the common method Of meas
urement being called the miners
inch method. The miners inch was
the unit upon which such measure
ment was based. being the amount
of water that would flow through a
sharp edged orifice one inch square
under given pressure. The guam
tity called for by miners inch,
however, varied in different states,
due to the fact that the pressure over
the orifice was not the same
Cubic Foot Per Second.
The cubic foot per second. which
represents a definite tangible amount
that is easily understood, was adopt
ed as the legal standard for the
measurement of water by the Idaho
legislature in 1899. It is commonly
known as the second foot" and rep
resents the flow of water which will
exactly fill vessel containing one
cubic foot each second of time for
as long period as it is allowed to
flow. Hence, flow of one cubic
foot per second delivers 60 cubic feet
per minute, or $500 cubic feet per
hour, or S6.4OO cubic feet in day of
twentyfour hours.
1t Is found that one cubic foot per
second equals flow of almost exactly
so Idaho miners inches, or $50 gallons
per minute. A flume one foot wide
and one foot deep, If filled with water
that is flowing at the rate of exactly
one foot per second, will carry one
cubic foot per second. and otner
fumes or bitches in the same proper
ton. The quantity discharged de-
ponds upon the velocity of the flow
and the area Of cross section of the
advancing stream OF water These
two factors are taken into consider
alton when determining the flow of
large streams and canals, 1t being
only necessary to determine the area
OF the cross section and the average
velocity, which two amounts multi
piled together gives the discharge.
The cross section is found by multi
plying the average depth of the
stream by the width The average
velocity is found by measuring the
rate OF the same either with floats
or with a current meter especially
constructed for the purpose. A close
approximation OF the velocity can be
secured by noting the time that is
required for surface float to ad-
vance through 100 or more lineal
feet OF the ditch. This gives the sur.
lace velocity, and to find the average
velocity one must multiply the sur.
face velocity by s.. since the aver.
age velocity is that much slower
than the surface velocity, owing to
the friction on the sides and bottom
Of the channel.
Acre Foot.
Where large volumes OF water are
to be considered the expression of
the amount In cubic feet would in
voive the use of such large numbers
that the same would be cumbersome.
In order to simplify these express
sions the term "acrefoot" is used.
which represents enough water to
cover an acre one foot in depth. or
1880 cubic feet The use of this
term has the additional advantage of
being easily compared with the acre
age; as for example, a reservoir con-
tanning $4,000 acre feet of water
would furnish a depth of two feet
for 25,0O0 acres of land. A cubic
foot of water per second flowing con-
tinuously for twenty-four hours fur
nfshes almost exactly TWO acre feet
OF water
Hydraulic Equivalents Which Will be
Found Useful to Irrigators.
!. Idaho miners inch equals ap-
proximately 1.50 of cubic foot Der
second. or nine gallons per minute.
2. The flow of cubic foot per
second equals approximately so min
er's inches, or $50 gallons per min
ute.
3. One cubic foot per second for
"a hours equals approximately 2 acre
feet
4. One acre foot equals enough
water TO cover an acre exactly a.
foot in depth. or 1850 cubic feet.
D. One miners inch per acre for
100 days equals 397 feet deep on the
land