Lincoln County times. (Jerome, Idaho) 1911-1919, 1912-03-07

land.
:. Fiveeighths miners inch pei
acre for 100 days equals 2.4S feet
deep on the land.
5 Fiveeighths miners inch per
. acre for $50 days equals So tees
deep or the land
2. One-half miners inch per acre
for 100 days equals 19S feet deep on
the land.
10. One-half miners inch per acre
for $50 days equals PCS feet deep on
the land.
Weirs and Weir Measurements.
) The most accurate. practical and
economical method of water meas
urement that has been devised for
the measurement OF comparatively
small heads of water is the weir
measurement. The weir consists es-
sentially Of thin notch OF a specific
shape. which the water is caused 10
flow over The amount OF flow de-
ponds upon the depth of water how-
ng over the crest. as the bottom Of
the notch is called. The weir has
been used for the measurement OF
water for hundreds Of years and the
method of its installation and the
discharge OF water can be measured
over il with an error OF less than one
/ per cent. if care is used.
There are several forms of weirs,
the name of each designat-
ing the shape Of the notch. Cippo-
letti. an Italian engineer. evolved
and perfected the weir which bears
his name. many years ago. this be-
ing the weir that is now most gener-
ally used in the west.
Weir Box.-In order TO maintain
the weir in a proper and constant
position and 10 prevent leakage
around and under il. and in order
that all water that is TO be measured
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 or
type OF this box which is recon-
mended for a one foot Cippoletti
weir is nine feet long. two and a half
feet deep and three feet wide inside
measurement, and with a one foot
weir will measure with accuracy
amounts ranging from ten to fifty
Idaho miners inches.
Where a weir box is built. it is nee
essary that il be made OF sufficient
size and depth in comparison TO the
size OF the weir notch TO eliminate
all excess velocity of approach. If
the box is built too narrow or too
shallow il will add 10 the velocity OF
10 such an extent that cor
rect measurement can not be Sc
cured. II is but mere matter of
convenience. however, 10 have a box
Of the exact length prescribed. for
that part of the box above the weir
may be omitted if settling basin or
pool OF the same size is constructed
in the ditch above the weir. The I
weir boxes and pools which should |
be constructed for weirs OF larger
sizes should be in the same proper /
ton with respect to the size of the |
weir as for the one foot. The size /
Of weir box that is required in order |
to eliminate velocity OF approach has
been found. by experiment. to be ap-
proximately seven times the cross
section OF the weir notch.
Discharge-The discharge OF weirs
has been accurately calculated by
various engineers who have carried
On hundreds OF experiments. cover
ing years of time. and it is found
hat under like conditions the same
iepth always produces the same dis
,harge over the same size of a weir
The conditions given for the con-
'truction and installation OF weirs
must be rigidly adhered to. however.
I accurate measurement is TO be
made. The formula which has been
evolved and which gives the dis
,harge of accurately constructed
,ippoletti weirs is
Q equals 1857 LHs-2.
Where Q equals the number of Gu.
nc feet per second. L equals the
ength of crest in feet and H EQUALS
he depth OF water on the crest in
eet, provided the same is measured
rom point level with the crest and
p stream from it at a distance equal
o the length of the crest.
l. The weir box should be set with /
IS floor even with the bottom of the {
itch and should be level in all direc. 5
ions. The weir itself should be ex. {
city level and perpendicular. {
2. The channel leading to the weir y
hould be of uniform cross section. or :
hat is still better. should gradually
nlarge as the weir is approached. ,
he axis OF the stream should pass
trough the weir and perpendicular
1t; or. in other words. the weir '
hould be located at right angles TO {
he middle of the stream. The ad- q
ancing stream should be free from a
thermal cross currents or eddies. as !;
lese have an influence upon the dis Il
barge II
). The water should be brought as A
early as possible to a state of rest Il
seore it enters the weir. An excess Il
elocity of approach due TO the We. Il
city of the advancing current will af- =,
ct tincrease) the discharge more ,,
ian almost any other one thing. =,
his velocity can be reduced by wild. =
ling and deepening the box or pool !
'ove the weir. 1t is calculated that '"
eirs three feet long with a depth of d
alter Of twelve inches, should not e
I've a greater velocity of approach
an six inches per second. which 1 -.
Mount may be allowed 10 increase NJ
ry slightly where greater depths