The Idaho Republican. [volume] (Blackfoot, Idaho) 1904-1932, 1911-12-22
less in the past about water meas

urement.
Miners Ineh-Water was frs
used in Idaho and other western
states for mining purposes, the com
mon method Of measurement beini
called the miners inch method. Tit
miners inch was the unit upon which
such measurement was based, being
the amount of water that would FLOW
through a sharp edged orifice one
inch square under a given pressure
The quantity called for by a miners
inch, however, varied in different
states, due to the fact that the pres
sure over the orifice was not the
same. The Idaho statute called fol
pressure of inches over the cen.
ter of the orifice while in Montana
law called for a 6-inch pressure. This
variation resulted in no end of -confu-
sion and as the miners inch was not
adapted to the measurement of large
streams it's use has been discontin-
ued for the 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 Ida
no legislature in 1899. 1t is COM
monty known as the second foot
and represents the flow of water
which will exactly fill vessel con-
tanning one cubic foot each second
of time for as long period as it is
allowed to flow. Hence, a flow Of
one cubic foot per second delivers so
cubic feet per minute, or $500 Gu tic
feet per hour, or $4,000 cubic feet in
a day of "a hours.
1t is found that one cubic foot per
second equals a flow of almost ex-
actly 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 car
ry one cubic foot per second, and
other fumes or bitches in the same
proportion. The quantity discharged
depends upon both the velocity of
the flow and the area of cross Sec
ton of the advancing stream of wa
ter. These two factors are taken in
to consideration 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
multiplied together gives the dis
charge. The cross section is found
by multiplying the average depth OF
the stream by the width. The aver
age velocity Is found by measuring |
the rate of the same either with
floats or with current meter espec-
tally constructed for the purpose A |
close approximation of the velocity |
can be secured by noting the time
hat is required for surface float to
advance through 100 or more lineal
'eet of the ditch. This gives the
surface velocity, and to find the aver
,ge velocity one must multiply the
surface velocity by eight-tenths, since
he average velocity is that much
lower than the surface velocity, ow-
ng to the friction on the sides and
,ottom of the channel.
While the above mentioned meth
IDS are those used by engineers and
'thers for the measurement of large
annals and rivers, this method is not
dapted to the continuous measure
nent of small streams and bitches
because of the time involved and the
liability for error where the measure
nents are not carefully made.
Acre Foot-Where large volumes
f water are to be considered the ex-
ression of the amount in cubic feet
yould involve the use of such large
umbers that the same would be
In order to simplify
hese expressions the term 'acre-foot
, used, which represents enough wa
er to cover an acre one foot in depth
r 43, $50 cubic feet. The use of this
erm has the additional advantage
t being easily compared with the
creage; as for example, reservoir
obtaining $4,000 acre feet of water g
'ould furnish depth of 2 feet for
5 1000 acres of land. A cubic foot {
f water per second flowing contin- 9
ously for "a hours furnishes almost l
xactly two acre feet of water.
Hydraulic equivalents which will
e found useful to irrigators:-
l. Idaho miners inch-approxim-
tely 1-50 of cubic foot per second,
r gallons per minute.
2. The flow of cubic foot per
SO miners l
lches, or 450 gallons per minute. a
8. One cubic foot per second for
4 hours-approximately acre feet. I
4. One acre foot-enough water to a
over an acre exactly foot in depth s
r 43,560 cubic feet.
5. One miners inch per acre for /
90 days-3.9l feet deep on the q
nd. t
6. One miners inch per acre for t
so days-5.95 feet deep on the land.
7. Five-eights miners inch per c
re for 100 days-2.4S feet deep on r
e land.
8. Five-eighths miners inch per
ire for $50 days-3.72 feet deep u
/ the land. c
y. One-half miners inch per acre v
II 100 days-1.98 feet deep on the Il
nd.
10. One-half miners inch per acre .
r $50 days-2.98 feet deep on the
nd. 0
Weirs and Weir Measurements-e
The most accurate, practical and ~