The Richfield recorder. (Richfield, Idaho) 1909-1931, 1911-12-14

& used in the computation of the dis
e charge. The Cippoletti weir motel
is trapezoidal in shape, having &
straight bottom or crest with sides
that slope outward from the vertica.
E at the rate of one horizontal to foul
vertical. A one foot Cippoletti weiI
has a straight horizontal bottom OF
t crest one foot in length with a width
between the sides OF is inches at a
: height of 6 inches above the crest.
/, If the notch is made of wood the
sides and bottom should be beveled
off On the down stream side, leaving
d sharp thin edge on the upstream
side. This is necessary in order to
secure a sharp clear-cut issuing
stream which it is necessary to Sc
cure ii accurate measurement is to
be obtained Ii is usually the best
policy to line or face the upper side
OF the weir board with a piece Of
galvanized iron from which the prop
or size and shape notch has been
cut In this cas- the notch in the
board should be cut slightly larger
than that in the galvanized ron
sloping or ~beveling the edges in the
same manner as before. The use OF
the galvanized iron or OJher metallic
4CoL - GHICtA0li1 GIOulllCuuGU 0S II
not only insures a sharp clear-cut is
suing stream upon which accurate
measurement depends, but in addi-
tion, it also furnishes a permanent
unchangeable crest for the water to
flow through. Provided the neces-
sary requirements are observed in
the construction and installation of
a weir. the amour of water flowing
over it depends upon but two factors
the length of crest and the depth
of the water on the crest. The
length of crest being known, the
depth of the water should be meas
ured, not on the crest, but from a
point level with the crest and up
stream from it a distance equal to its
length.
Weir Box-In order to maintain
the weir in a proper and constant
position and to prevent leakage
around and under it, and in order
that all water that is to be meas
ured should be conducted over it, it
is usually necessary to construct
some sort of box or frame to hold
the weir in place. A common form
type of this box which is rec
commended for a one foot Cippoletti
weir is 8 feet long, 2R feet deep
and 3 feet wide inside measurement,
and with a one-foot weir will lea
ure with accuracy amounts ranging
10 to so Idaho miners inches. !
Where a weir box is built, it is
that it be made of suffic- !
lent size and depth in comparison to
the size of the weir notch to elimin- {
ate all excess velocity of approach. If I
box is built too narrow or too
N oIlnu II will odd f0 fhn Un1noifu nf Il
approach to such an extent that cor I
rect measurement can not be secured. {
It is but a mere matter of convent ;
ence, however, to have a o of the |
exact length prescribed, for that part ,
If the box above the weir may be l.
if a settling basin or pool of I
he same size is constructed in the .
Itch above the weir. The weir box =
IS and pools which should be on u
for weirs of larger sizes ,
ihould be in the same proportion y
With respect to the size of the weir T.
is for the one foot. The size of weir =
that is req ired in order to elm !
nate velocity of approach has been >.
ound by experiment, to be approx ).
nately seven times the cross section :
# the weir notch. y
Discharge-The discharge of weirs L
las been accurately calculated by :
engineers who ave carried a
n hundreds of experiments covering y
ears of time, and il is found that 8
like conditions the same depth =
lways produces the same discharge =
yer the same size of a weir. The =
onditions given for the construction =
nd installation of weirs must be rig ;,
dly adhered to, however. if accur- y
tie measurement is to be made. The =
which has been evolved and :,
hitch gives the discharge of accur- =,
tely constructed Cippoletti weirs is =
equals 1867 L H 80 -
Where @ equals the number of GU -
bic fee per second =
equals the length of crest in feet =.
H equals the depth of water on p
the crest in feet, &c
rovided the same is measured from ~
point level with the crest and up u
from it at a distance equal to u
ne length of the crest. In order to =.
acilitate the determination of the ~
ischarge over weirs and to reduce -
ne liability for error to a minimum, ?.
lbles of discharge for weirs have %
cen compiled. These may be Sc -
lred from my office or from any D
eliable book on the measurement of
alter.
Throughout all of the experiments be
pom which the weir formula is based CT
ertain conditions have been observed TO
it'll regard to the setting and plac-
lg Of the weir and these conditions 10
lust be reproduced if it is expected tn
!, secure accurate measurement. If SO
lese conditions are rigidly carried 10
ut, water can be measured with the
.ippoletti weir with IN error of less th
ian l per cent. These conditions or
pply equally to all weirs whether &C
iangular, rectangular or Cippoletti di
1. The weir box should be set with
S floor even with the bottom of the w;
and should be level in all direc- an
ons. The weir itself should be ex-
lily level and perpendicular. a
2. The channel leading to the weir tn