The Blackfoot optimist. [volume] (Blackfoot, Idaho) 1907-1918, 1911-12-28

This method eliminates the effect
of capillary attraction ON the rule, but
is not practical for farmers weirs on
account of the expense of installation.
Ii care is used, the head can be meas
ured accurately enough for all practi-
cal purposes with an ordinary rule in
til manner previously described
The most frequent cause of error
in weir measurements is excess vel
ocity of approach and this must be
guarded against by providing a good
sized pool above the weirS which must
be kept clean and free from sediment.
"Dont's' in Regard to Weirs
l. Do not set weir Immediately
below curve in the ditch, for the
curve will cause the water to flow to
the side of the crest.
2. Do not set in Immediately below
, or too close to the head gate where
the water has high velocity, as by SO
doing. it will cause too high a veloc-
itv Of approach.
8. Don't allow the water below the
weir to back up even with the crest
as it will not allow complete contrac-
ton and will cut down the discharge.
A. Do not set the weir any other
way than perpendicular and at right
angles OF the flow of the stream.
5. Do not attempt to use too small
weir. Put in a large weir Put in
larger weir where the water to be
measured exceeds a depth on the crest
of 1-3 the crest length.
g. Do not allow the pool above the
weir to fill up with sediment, as the
resulting decrease in the cross section
will increase the velocity of approach.
Duty Of Water
To know the proper amount OF irri-
CATION water that should be applied
to the different crops in order to make
the greatest possible yield, has always
been a serious problem to all irrigat-
ors 1t has always been known that
in order to secure the biggest possible
crop it is necessary to apply different
amounts to different crops and to diff
ferent soils with the same crop, but
just how much this amount should be
has never known only in an indefinite
way.
The Irrigation Investigation Depart
ment which l represent in the State Of
Idaho, has, in cooperation with the
Safe Engineers office, been carrying
on a series of experiments fir the past
two years by means of which is hoped
to determine this important factor and
we have secured vast amount of da,s
concerning it. These experiments hav
all been carried on comparat lively larg
areas and in a practical way.
1t does not give any indication of
how much water is necessary for max.
ium 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 beel
produced with either more or less wat
err than that which was really used
SC We have been trying to work out
this feature by selecting large num-
Der of tracts on typical farms in diff.
, ferent 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 manner on 60 diff
ferent farm during 1910 and on as
b many more during past season. Sew
t eral factors in regard to the use o.
/ water have been very strongly empha
sized, the principal ones being tina
r the amount of water required depends
} upon: "a The character of the sol
3 ard sub-soil. The texture Of the sol
: as regards porosity has mare to d.
with the amount Of water used thar
r any other one thing and it has beer
t found that adobe soil may be irriga
d ted with total appleton of but
or 3 acre inches while in some instan
r ces from / to acre feet are requires
t to spread over and thoroughly irrigat'
8 an acre of very gravelly soil. At leas
e % of this latter amount is almost in
\ variably wasted as it either passes int
t soil is underlaid with an imperviou
the ground water or percolates beyon
d the reach of the plant roots. II cours
4 stratum, the amount Of water neces
e sary is materially cut down. while l
g the impervious stratum is lacking
t some irrigation system must be use
e which will flood the ground Quickl
t. befor the water has time to penetrat
h too deeply If a high duty is to b
:. secured.
A CO Climatic Conditions. The am
g ual, PRECIPITATION and, its seasonal dir
e tribution, together with the temper
ature. humidity and wind movemen,
v all have very evident effect upon tt
r amount of water required.
( (S) DlVerSlIlcauOn OF farm crops
r Where farm is all devoted to on
e crop such as grain, hay or potatoes
@ the greatest need for water usual
ID falls within comparatively short tim,
It ard there is but little use for it dul
le ing the rest Of the season, while by d
= versifying his crops, the farmers nee
q for water will be more constant an
S he is better able to make good us
} a continuous flow of the dilch throug
o out the season.
gl az Use of Rotation.-t is we
e known to most irrigators that littl
r can be accomplished by irrigation wit
n small heads of water, and much lar
e. er and better use is secured from tn
+ water where larger, heads can be use,
e Rotation systems, by means Of whic
q farmer can exchange water with b