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* U N I T E D STATES '" * : DEPARTMENT : O F THE INTERILOR • * :

* BUREAU OF RECLAMAT~I'ON , : *

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H Y D R A U L I C L~,BOR~,TORY R E P O R T N O ; ~ i 7 9 " .... ! ~:i: .~ ......

* J ' iYDRAULIC MODEL S T U D I E S " : O F . . . . .~- * * ALL -AMERICAI~ !CAliAL CHECK S ' [ A T I O N I 6 0 ~ O 0 _ + . . . : * ' * ALL -AMER I CAN CANAL::SYSTEM - , , . . . . .CAL:;I F O R N I A * ; ," ' , ".i:~..* P ~L

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" FRED L O C H E R , SOCI ATE E N G I N E : * - :. "::,

* D e n v e r , , C o l o r a d o • L:''~" * May ii~, ~9~i . • --~. ,'

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. UNITED STATES .

DEPARTMENT OF T ~ INTERIOR

BUREAU OF RECLAMATION

HYDRAULIC LABORATORY "REPORT N O , 172-

SUBJECT., HYDRAULIC MODEL'.STUDIES OF-TH~ ,:. ' "

AU,-A~R'r CA~r CnV.~ ~ ~. CX s TAr ~ o ~ 60 ~ ±,i

ALL-AMERICAN :CANAL SY~

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By FRED LOCHER, .ASSOCIA?E ~NOINEER

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Under .D~ec%i, on ~o£

J.. E. ~RNOCK, SEN/OR ENGINEER '

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.De~ver, Colorado, May 14, 1945

7 . • :

UNITED STATES DEPARTMENT OF THS~ INTERIOR

BUREAU OF RECLAMATION

Branch of Design and Construction Engineering and Geological Control and Resee.-ch Division

D ~ v e r , Col~'ado ~.~y 14, 1946

Subject, Hydraulic model studies of the All 60+00= - All-American canal system, Calif6:

c~

2

Lecher • Warnook

_ok. station

1. Gene ra l . S inoe t h e Al l -Amer ioan cana l h : : : : : . ' : as bee n placed mn open.

tlon. the discharge from the desilting works into the canal has not ex-

ceeded i0,000 second-feet and this was maintained for only a'short pet':i::

led when wRter ~s being diverted into Mexico. At present, the steady .... .

flow varies bet~veen 4,000 and 6,000 second-feet.

Because the canal was designed for m~xi~ discharge of 15,188

second-feet and no cheek was provided for . oiling water surfaces

at partial discharges, exceesively high velocities occurred in :.the Chan.

nels e~nd effluent v~irs a~ the desiltin~ works° The resultingl scour re-

moved the ssnd from beneath the dry-rock paving causingwashouts in the ~

channel which were so severe that it v~s necessary to suspend operatic~

of ~he canal while repairs were being made, ' -,

The scOUr and o+~her operating difficulties could be eliminated by ',.i~

check-drop structure downstream de ing " " ~:: the use of a from the silt works,. :'-!:::

which would maintain the water surface nearly constant at the maximum i/i""i;i

dspth of 20.61 feet for all flows and reduce the velocity in the oha~els

at the desilting works to a value below that which is capable of produc-

iu@ scour.

Investigations of the hydraulic properties 'of a check-dropsitus-.

ture in the canal revealed that maintaining the upstream water dep~h

constant at 20.61 feet, in combination with the various dOWnstream water

surfaces expected at the different flows, a hydraulic Jump

form. At all of the disohar

depth too eat for a J=p to .nd eondit .oaned.,

jump" would exist. When this occurs the

dissipate rapidly and carries through the

bottom soour and bank erosion, especi~lly in the sandy soil:.w~ich o l d . r - o

aoterizes this part of the All-American oanal. ~r

The uncertainties .surrounding, the, character of the flow and the

desire to ob~aln the most economical structure that ~wouldaerve the r e - L" ~r~

qulrements and provide ample protection, against downstream erostom lead

to the insti~tion of model tests, L r ~

2. Initial tests A The desi~ shov~ on figure ~ '~ "

I z SO scale for the first~ tests, It was a . . . . 7--gate str

with the c a n a l bottom aud-without transitionS. The banks ~-

a 1-3/4:1 slope with the triangular area :bet~veen~,the oUts . ,.

the slopes closed by a solid oonerete ,wall. Initial tests of-this .de-

sign indicated considerable bottom scour , and. in addlticm, , : l a rge V~tloes

having sufficient velocities to oause bank erosion formed a[a~-ust~the ~ : •

c a n a l banks a short distance downstream. Both of these c~ndi~ions were

oorreoted by the addition of dentates between the piers; The dentate~

produeed a "choppy" Water surface which was ,considered undesirable i~i :- -

view of previous difficulties with o a n a l bla~k erosion, due t o w~ve ao-

tion.

f

; !.~'i~!~ ~ - i~i ~ ~/i~i~-~ i~i~i!~I~/~:~ 17: ~ ~:

To obtain a"measure of the relative roughness .of the water surface,.

between models, a condenser ~r~e.of surface gage was deveiouod, The

instrument was designed so that the variation .af.the air 'gap between ~

one of the condenser plates and the water surface upset am electronic

brid~e and caused a small current to flew throu~oh to ~he connected

oscillograph, The greater the .el ~e mere current ~flc~,

hence, producin E a greater defl ec Logograph galvanometer,

If the air Gap remained constant which would ocrresp~d tO no " ~i , ves i n

the ~odel, the position of the li~oht spot did not change, %~hen the

p a r a t u s w a s installed i n t h e m o d e l the condenser ~ p l a ~ t e s =d a m p l i ~ h j ' i n g " ' "-,~/ ' i

e~ipment were mounted on ..the end of ~a noint ~ a ~ o ~ ~ o~ ...... ~ it ~possible te ~

set the condenser plates the sa~ distance from the average',w~ter sur-• i

fsce for @ach test. As the instrument was not line~,ithe oscillo~.~

obtained did not indicate the actual amplitude of the wave and-served

only to indice~ if the v~ve amplitude in one desi~n~was greater ,or

lesser than in another design. ! ~

The equipment was not completed at the time tl~e il.i~ia~l~ tests .were "

made and no record of the water surface was ~obta~led for .either ~the :"i'~:'~

original installation or the same arrs~uge~ent vritbdentates .!placed be- " ~"!;ii!i

tween the piers. ~ ~

3. Designs for minimum v~ve faction. By increasing the submergence

on the model of the original design the roughness of the dov~tream wa'

ter surface decreased considerably so the next test consisted of de-

pressin~ the downstream part of the structure 7, 5 feet below the canal

~ade and maintaining the gate seat at the canal 5rade. The t~'~nsi~io~

between the two levels was effected by a 45-de~ree ,slope. ,'A row ;of

dentates 45 inches high was placed Ineaoh pier section downstream ~ ,-

from the 48-deGree slope. The arraugement was not satisfactory because C

"the jet did not follow the 45-degree slope :and rendered.lthe in_

effective. Side eddies also formed,which added, considerably,to the _,

roughness of the water surface. These difficulties ~were Overe~i.~by , .... ,

causing the gates to seat on the 45-degree slope ~and increasing the

length of the two outside piers. The osoillogram, of...thelwater surface

is shov~ on figure 2A, where the transverse ~.lines r .i0 second

on the model, • .....

Due to certain design difficulties inherent-.with seating the gate •

on the 45-degree slope and with sliding friction for stability the ~i"

structure, it was decided to ilmver the gates as shown on.figure.3; .~:"

Tests with the design gave the most satisfactory +water ;surfaoe:i+iof all

the designs .tested, figure 2B, In. the model the.bank erosion" due;tO ....

wave action was negligible and the bottom sOou

cost of this structure was $150,000 more .... ~ .... i g n .

To r e d u c e .the c o s t , t he - s t ruc ture-wa~ ~es i n . ) -

stead of the original seven. .Otherwise ,the. -'design.. was ~the same as ....... "

shown on figure 3. This increased t,.~e roughness Of the-water sum'face,

2 0 , a n d c used e,.osion or both the. e-b -

. / ! "

performance of the five-gate rarrangement could.have been .obtained bY. :~:i}

lowering the bottom of the gate seotlon, stil~i £arther below the canal ..~

grade b u t a s ~this ::~m~uld n o t have been a s a v i n g in c o s t , , t h e f i v e - g a t e

design was n o t g i v e n a n y f u r t h e r oomsideratlcn, • "j

4

A suitable compromise design was. developed fret, a }~draulio view-

- " ' r point by changing the elevation of the :seven-gate arrangementofiigure ~-:'

3 to a point 2.5 feet below the canal grade.~ The,tests:"did.n0t- indi.

care any bottom scour and the

cause auy serious bs~k erosion

sign was more than that of the

ther considerati cn~ -~

did not

is de-

an fur- -

4. The selected desi~ As itwas not POssible, t0 obtain:a ::~/ ~~

hydraulic jump below the '/ ~ ~;ates reith tlhe.!bott0n{ of :~the structure o r

below canal grade the fleer, of the check t,hrou~ the L-on ~was

raised 5 feet with a 7,I slope from,, the down:

canal grade. Assuming that :.a Jump would fern

condition would be obtained for all flows b~ .~At

fl~gs above II ,000 second-feet, t~e drop tlu ~

dueed sufficiently to be of no great importance so le_r ~ as energy dissi. ~ / :

pation was oQnoerned. "

Tests vr i th the design sho~edthat a hydraulic j~np all

fl~s up to and including i0,000 second-feet and that at 12.000 second,

feet a semblance of a jump was still present.- Hoverer.. in ~the previous-

designs the worst condition for r o u ~ m e s s of the water ,surface occurred

at i0,000 second-feet for which the records, were ~taken, but with t)~is

arrangement the worst oondition~vaas obtained ata dischayge of 12.000 •

second-feet. In addition tl~re was considerable scour at flows bel~v

8.000 second-feet due to interference of the piers .when the jump formed

dc~rnstream frc~ them. The absence of downstreem flow in the area

. I

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adjacent to and immediately downstream of the piers caused an upstream ,

f l o w in this area, This eVe~tually b~oe~a~ ~ ~tabie,,~'d~g~ ~: i;

shifting from one gate seQtion to another, which seriousi)disrupted .

the Jump and p r o d u o e d large eddies and ~ttcm soour.

was o=reo d by

fi~e ~. This o a u s e d .~the jump to

fl mrs. The scour was eliminated b~

7,1 slope as shown on figure 4. Th

the Jump between the piers at ic~ flows.

Wave action was most pronounced

feet, figure 2E, and by :comparison wi~

figure 2 the most severe wave action .was obtained

Thb waves were only a s~.~faOe condition.

• . ~ ?~

at

on .he

in g

mush more than 200 feet d o w n s t r e a m fro

that 200 feet of riprap on the banks, :and 150 feeti: on ~he ~ i - ! b o t ' t ~ , ,do~n- -"

stream from the s~ructure would be adequate prol ....

A satisfactory hydraulic jump will fOrm'on a '~ . .... ~ .. 7::I slope extending .i~

s/i indefinite distamoe below the Water surface. ....

A considerable amount of wave action will occur beiow a hydraulic ii~iJ

jump . . . . ~'-~ .~ J

formed satisfactorily, it was selected for

less costly than any of the previous designsand

O~ ~ The design flo"~e 4 wlth the additional

~installation,

i

Wave action resulting from ener~- dissipation oen bs eliminated ,,,! - : i

by sufficient subm~rgenoe of the jet.

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. . . . SECTION .J, " "

C.ECX S T A T I O ~ ~ 0 * 0 0 --

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