Elmore County Republican. [volume] (Mountain Home, Idaho) 1910-1915, 1912-02-03
CONSTRUCTION OF WEIRS AND HOW To PLACE THEM

mers Welrs ON account OF the eX-
pense Of installation. Ii care is
used, the head can be measured
accurately enough for all practi
cal purposes with an ordinary
rule in the manner previously de-
scribed.
The most frequent cause OF En-
ror in wier measurements is eX-
cess velocity Of approach and this
must be guarded against by pro-
viding a good sized pool above
the weirs which must be kept
clean and free from sediment.
Don't 81 in Regard to Weirs.-
/. Do not set a weir immediate
ly below a curve III the ditch, for
the curve will cause the water to
flow to the side of the crest.
2. DO not set it Immediately be
low or too close to a head gate
where the water has high yelocit.
as by SO doing, it will cause too
high velocity OF approach.
3. Don't allow the water below
the weir to back up even with
the crest as it will not allow COM
plete contraction and will cut
down the discharge.
4. Do not set the weir any other
way than perpendicular and at
right angles to the flow of the
stream.
5. Do not attempt to use too
small Weir. Put in a larger Weir
where the water to be measured
exceeds depth on the crest OF
1-3 the crest length.
6. Do not allow the pool above
the weir to fill up with sediment,
as the resulting decrease in the
cross section will increase the vel
ocity Of approach.
Duty OF water-To know the
proper amount Of irrigation wa
ter that should be applied to the
different soils and crops in order
to make the greatest possible
yield, has always been a serious
problem to all irrigators. 1t has
always been known that lin or
der to secure the biggest possible
crop it is necessary to apply diff
ferent amounts to different crops
and to different soils with the
same crop, but just how much
this amount should be has never
been known only in an indefinite
way.
The irrigation Investigations de-
partment, which | represent in
the state Of Idaho, has, in cooper
alton with the state engineer S Of
flee, been carrying ON series Of
experiments for the past two
years by means Of which it is
hoped to determine this very inn
portant factor, and we have Sc
cured vast amount OF data con
corning 1t These experiments have
all been carried out on compare
lively large areas and in prac-
tical way.
1t does not give any indication
OF how much water is necessary
for maximum crop production on
any soil to merely measure the
amount that some farmer applies
for the reason that the same or
a larger crop might have been
produced with either more or
less water than that which was
really used, so we have been try
ing to work out this feature by
selecting a large number Of tracts
on typical farms in different parts
OF Idaho and then divide each
tract into three different parts
and apply different amounts Of
water to each one. Water was
measured and varied in this man
ner on 90 different farms during
1910 and on as many more during
the past season. Several factors
IN regard to the use of water have
been very strongly emphasized,
the principle ones being that
the amount of water required de-
ponds upon. (1) The character Of
the soil and the sub-soil. The
texture of the soil as regards por-
oslty has more to do with the
amount Of water used than any
other one thing and it has been
found that adobe soils may be
irrigated with a total application
Of but 2 or 3 acre inches while
in some instances from ! to 2
acre feet are required to spread
over and thoroughly irrigate an
acre Of very grayelly soil. At
least 2-3 Of this latter amount is
almost invariably wasted as it
either passes into the ground