The Oakley herald. [volume] (Oakley, Idaho) 1908-1961, 1912-04-05
Duty and Measurement
Xxx Of Water &&
Dy DON n. BARK, v. s. Engineer,
In Charge Of irrigation Investi-
cations In Idaho.
Oregon Short Line Railroad Dem
onstration Train Lecture.

The greater part OF the land in the
west would be practically worthless
without water with which to irrigate
It, 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 800 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
nent 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
tho orifice was not the same.
Cubic Foot Per Second.
The cubic foot per second, which
represents 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. 1t 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 a period as it is allowed to
how Hence, flow of one cubic
foot per second delivers 60 cubic feet
per minute, or $500 cubic feet per
hour or $4,000 cubic feet in a day of
twenty-four hours.
1t is found that one cubic foot per
second equals flow of almost exactly
80 Idaho miners inches, or $50 gallons
per minute. A flume one foot wide
and one foot deep, if filed with water
that is flowing at the rate of exactly
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, it 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
face velocity, and to find the average
velocity one must multiply the sur
face velocity by g, 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
that the same would be cumbersome
In order to simplify these express
sions the term "acre-foot" is used
which represents enough water to
cover an acre one foot in depth, or
43, $50 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 $4,000 acres of land. A cubic
foot of water per second flowing con-
tinuously for twenty-four hours fur
nishes almost exactly two acre feet
OF water
Hydraulic Equivalents Which VIII be
Found Useful to irrigators.
1. Idaho miners inch equals APP
proximately 1.50 of a cubic foot per
second, or nine gallons per minute.
2. The flow of a cubic foot per
second equals approximately 80 min
er's inches, or 450 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 1860 cubic feet
5. One miners inch per acre for
100 days equals 3.97 feet deep on the
land.