PARTMENT OF AGRICULTURE , •?.
ICUL. TURAL. ENGJNEER.NG INGTON, D. C.
Mr. R.L~ Parshall,
Sr. Irrig~tion Engineer ,
Colo. Agr. Exp. Station,
Fort Collins, Colo.
DIRECTION FOR LAYING OUT SILT VANES /
HL __
I,o
I I J \ \ \ \ tj\\ ~ \ 0 \ ~ \ '"' \ \ N, - \ \ 0 \ _, \ \ \pINDEX SKETCH PLAN Or .5tL T VANES
>> > >
Width of Channel= W .r For Value of X strong
"
effect Cheaperf
'
design (less n effect) ·l " Minimllilr dimen- n sions recom.rn-ended"
"
nY
n R " X Tf y nR
X"
y nR
TABLE OF DIMENSION;: FOR SILT VPJ'TES
( To accorr1panv fllrawing) 2 4 6 8 4 5 6 6 2 3 4 5 30 35 40 40 3 4 4 5 2 2 4 4 25 30 30 30 3 3 4 4 2 2 3 4 25 25 30 30 10 7 6 45 5 5 30 5 5 ~0 12 8 8 45 6 5 30 5 30 16 8 9 50 6 6 35 6 6 35 20 9 11 t>O 6 7 35 6 7 35 25 10 13 50 6 9 35 6 8 4:0 30 10 15 55 6 12 40 6 10 40 40 50 12 12 20 25 55 100 9 15 50 6 10 40 g 18 75 6 12 50 100
NOTE: The above figures are only intended as a rough guide a:cd must be varied accor d-ing to the circumstances of each case. For ex~ple R should be greater for a large parent channel than for a small one , also X andY woul~ ordinarii- be
)made larger for a large and deep parent chanr,el than for a small one. rrhe design
mi~ht further be cheapened by omitting or reducirg the bed pitching upstream
1of the vanes, but this is not recorrnnended as it vitiates their effect. Similarly
for the cement plaster on the 'vanes. In very bad cases Y should be made greater
DIRECTION FOR L~·YI. . .TG OUT SILT VANES (To accompany ara ~ling)
From the upstream edge A of the off-taking head draw
a line A, B at right angle to the centre line of parent channel, of ~he lengt specified as X in the table of dimensions.
Through the point B draw a line CBD at an ancle of 2 to
1 with the centre line o1' the parent channel, cuttir-g the edge of the parent c~annel at C, upstream
or
the off-takinghead.
Draw another lir'e EF parallel to -.he centre l ir::_e of the parent channel and one foot a~a~ from the toe of the side
pitching.
Or where it s _ould be , cutting the lir:.e CBD at G.
Pou find a centre
H
such that ar arc of radius R (of l engt h specified ir- the table of dimensions) , will touch both the lines CBD and EF this ~iJl best be done by bisecting the angle DGE from H dravJ HK at rigllt angles to the centre line of the parent channel.Vli th centre H and radius HK draw an arc of a circle KL
of such length that the inclination of .hL to Hk is 2 to 1. The curves must all end at the lines HK and
HL
.
Now from the downstream edge of the off-taking head draw a line .~ in a direction upstream from M aLG at an angle of 2 to 1 with centre line of the parent channel.
Fr01.t1 L lay off a distance LP along the line CBD such as to project 5 feet (or less, as may be desired) beyond the
n Optical Lever 3iltometer -
By
Dr .V
.
I . Vai'hicnathanProceedings of the lunjab Engineerj ng Congress - Pa- er Fro. 167
Theory:
Brass tube 120 centimeters long, 7 centiLeters in diameter,
ith s~Qecial mercurJ :U1anometer attached to the side V!it1 poi_t
about one-fourth from the bottom. Silt aa~ple placed on pan
at top of tube, tripped electrically. as the silt descends
in the uater column the densi tv is ir~creased as the mass passes
manor11eter conJ.1ection. 'I his incr-ease in mass raises the
mercury colwm:: thus displ6.cir...g tl~e optical lever. Reru 1 ts
recorded graphically on a photographic chart. One-fifth sec
-one intervals also reco~dei for- co_parison. This ~thad
said to be useful in determining the diameter of particles
according to Stokes' Law.
Silt Conduction by Irrigation OutJets - Pandit K.R. Shanm
Proceedings of the Junjab Engineering Congress - Paper ro. 168.
This pape~ uescribes desigh of outlets from a canal such
that the outlet 'Til~ divert its :nroper share of the si 11
load in the canal thus preventing deposition •. Conclusions
were tLat wten the outlet was diverting water at a .6 depth
most satisfactory resu.J ts Yiere obtained . 1
J1his VIuS \;·;hen the
amount of silt taken out varied fran 100 to 115 nercent of
that carried in th_ channel.
Silt Exclusion from Distributaries - H. V. King
Proceedings of the Pujab ~n~ineeriLg Congress. 1933. - Paper 169.
The general discussion is co~cerned \Jith the use of silt
vanes in the exclusior of silt frau entering offtakes
which consist of c. series of parallel curved vnnes set about
2 feet apart and from .5 to .8 of the depth of water in
height. The radius curvature veins from 15 to 30 feet .
It is reported thst the effect cf such obstructions is 'ery
marJced and posE;i bJ y sonething. of this nature v~ould be found
Ar1·0pticrl Lever ';iltometer- Lr. V. I . Vaidhianathan
Proceedings of the Punjab Engineering Co· ... gress. ~933.
p. 216-228. Paper No. 167.
Silt Conduction by Irrigation Outlets - Pand.it E.R. Sharma
Proceedings of the Punjab ~ngineerjng Congress. 1933.
p . 2f9-262. Paper No. 168.
Silt Exclusion from Distributaries. - H. W. King.
Proceedirgs of the :'unjab EngineeriLg Con~ress. 1933. p.
