400. Seepage from irrigation channels (revised) April 25, 1947

UNITED STATES GOVERNMENT PRINTING OFFICE

DIVISION OF FUSLIC DocumENTs WASHINGTON 25, O. C.

OFFICIAL. BUSINESS

PENALTY FOR PRIVATE USK TO AVOID PAYMENT OF POSTAGE. aloe

40F01

Colorado State College of Agriculture & Mech Arts Dept of Civil Engineering

Fort Collins

THE UNITED STATES DEPARTMENT OF AGRICULTURE Soil Conservation Service

Division of Irrigation And Water Conservation

SEEPAGE LOSSES FROM IRRIGATION CHANNELS by

Carl Rohwer and 0.V.P.Stout

V. S. SITAXIMSST ASILIMUM1 SOIL SIMISWATICal =MO

Ka Iliessetto Chief

SUP= LIM not am Of Carl SAW

Sag. Irrisstima linsboor

0. V. F. Stoat Irrigatios

Cliania

**awn:utile bon Us

Division of Irrigation cal ilatOr Consonstion in 000perction WA the

Colorado urioultural liverct nation sal

Oalitornis AvianAural imperineat heti*

ram siimasio 4116GRADO Sartb. 1947

Propired under Ow dirootion of Wow D. ilkydcip Oleo Division of Irrigation and Utter ConocriroUctil I. I., lieholoo Chief of Semaarobi.

UM* isail= PIM laltiCAT CRAN*18(1)

Carl Itahoero Senior Irrigation Itagisoic O.V.P.

sad

Stout', Irrisaties SigineimP

ISTRODUCTIOS

Mehrly onembandred aillismeere•teet of eater is diverted annually from stream!, reservoirs and orimasikamater basis* to irrigate *reps is the arid regions of the West. hes onem.third to one.half of this sesust is lost before it reaches the farmers' fields. Seepage probably satannts far the major portion of this lees at meet Irrigation projastes and sins,

meter is the limiting hater in theigrienitural development of this regime, it is important that efforts be made to reduse the seepage less. dimoosimidemookomp.0.

(1) Most Of the field sort covered by this bulletin vas somdested by the authors in California under a eesperativoogreement bets'.* the Diviatoa of Aploultural liegimeeriogi Borman of Potblie leads and the California Aceioulterel isperiseat Statism. Dr, Samuel Fortier, Assesiste Chief of the Division of AgriemItural tail* awing ins in dhow for the Demi of Puhlle Reeds end Pretossar Prank Adams for the Califeraia Aerlsulturel *pediment Mattes.

After the death of Major O.Y.P. Stook the prolest ems assigned to Carl Ankmer, oho sompleted the revert or the direetlem it W. 14 MeLemghlin, Chief it the Division of Irrigation, Soil Ccfneertetion Servies. This week ems Sinted as under a seepow

tive agreement between the Soil Ilesservatioallervioe sod the Colored* Agrimaltural Uperimmei Station'

,olnehle assistaces lathe prspsrstion at this report vas

resolved free the melhers of the Division of Uri/Attie% eifielals it irrigation projeeteo sod sagissers• at the Alrean of Reelanation,

which is gratefully moknewled4pd. (2) Deseasede

ikerever„ Wore Ind esseerretion NOMA* 'eabs deistopedip a 'earetul study. *fan the factors that inflames seepage losses eget

be med.. Various ageneles have investigated this prOblee in the past, but it vas not until 1922 that a somprehinsive study at the proOdee was initiated by the Division of Irrigation, United States Department et Agriculture, in oeoperatiandth the California Agrieeltural

west Station and other ageneles, This pro,set eoneisted of a study of the factors that cause seepage, the divelepment and testing at various methods of esas,:xing seepage and the SINUOUVINOnt at seepage losses free lined and unlined canals, laterals and farm ditches under different

flys *auditions, Work on this project has been carried on intermittently sines that date as Stade land pereemmel etre available, The results of Owe ~leo are reported La this bulletin•

Aseerdiag to the lest Palma seaous(33) there ware 3.25,034.8 silos of canals and laterals sad 28008.3 ails* of pipe limo used is Whiting irrigation water supplies to florae in the 17 'twisters States in 2.9194) (U, tole 1) Ot the easels sad laterals a total of 4,64SO miles had

been llama, $o data ere available as to the length of small ditebes used in distributing eater on the farms, but the total is probably fir is **VMS of that for eantas and laterals, Although the seepage lees from acme minas is relatively all, many esnsls lose * large proportion

of the ester serried and the aggregate the lose is trmsemisish The pereestege

or

the eater diverted free serfage supplies tor irrigation that is lost

tyr

seepage, evaporation sad leakage Uwe of the Western States is else set out in ?able 14 These pereentages were

X1* _j, Summary of irrigatea trr1gfttiGt 'atter deliveries louses And Isastos of *Mammal* of

'traria** *pee required to doliver irrigation. water stylies in the 17 Swaim Statism.*

Ito. :Ante irri iixisona Ckliforata 03040 5,J6905(118 3 Coiorado 4.120,485 4 idabo 4277,457 5 Masai 19,980

o

illoatana 1,711,44 7 Imbouska _t4144.09 8 Nevuda 739,463 9 Smoorlimi00 554104 10 Peril% Dakota 21061$ 11 °kW's.* 4,161) 12 0144.1 4049,176 13 South Dkotra 60„1-#4 14 reams 10045„.r24 15 jteh Isabvii6 16 Wahington 415,013 17 _{itylonin .4etii•/.98}

utias

2U,3950a43 total water

daiiverid Total L063 Setwoln

to Nreers .nd Delivery

Laugth Diverting

Total

of Gftnals and Late 114400r from Cutlass &alb Lisisd ra,la Supp or lime Louth Pipe Lin*. ker.-foot ?oreAkt 4'r144, 334 0,419,42 *7513,458 9,Y19,232 46 11043110000 17 1,59U034a 31 4,224J3ki 160,50, 24 3,369,609 41004 2,10,46 19 1,446,418 55 39,309 60 5,611 3119607U6 21 58,797 55 2,436,310 48 2,914890 20 3,42033 27 2.431A61) 67 1040** 42.2 145upOw ta,516.4 4400a 1,049.3 2,a5‘.4WU 5,436./ 7,13iO4U 9tou4.5 1020404 4,248.6 41.114 ,,wa 141624 4.176.2 3,966 190799.1 18,217 19064.0 19,701 13,602.1 13109 oidoot* 292.5 292 2,440,JW 15,702.5- /54555 374,WQ 3,331.3 3,267 5060 4897.2 2,445 .4.1.5660.0 4,647.9 4,567 5900;-4 159. 15$ 41 3.47.2 • 1,0)S 4,944 3,581 744 55,6o1,326 3 34617,5io 1,z5,J34.8 1",;4,386

* ,4410mgIod from 1.940 Irrigetion emaslati of the Jutted Statme.

** Data imeonsietent, logos sotimatmd.

157.0 L13.1 0.5 147.5 44.3 52.2 1.2 1.2 4296.0 11.3 992.1 262.5 u67.6 47.4 4,643.8 J44.3 44644.2 :L45.1 29‘).9 4.1 146.1 36.5 3.5 24.4 -465.2 17.3 923.1 24(112.1 474.4 ze • _5vd.

diverted free surface scums and the savant of water delivered to the farmer, per sore of irrigated land. They do not purport to 1:010 the tree

values because they are based on only a pert of the area irstgatei sal furtheramee, the area for ehieb, the total diversions were gestured may sort be the same as the area ter

*la

the total deliveries to the farmer* lore aleasurei. The pereeategeo are, hewer, based 'snob large agree,*

that they are believed to be representative. The data shoethst the lows rang. from 17 to 67 perseet of the total diversions. Them velum

are preblar tee high Weems, at the tendemey to giro fell measure to the tinier lbw making deliveries mad froom thee.' the oilmen termed est average* lees than 10 versant the attest ea the 'enema* ellepeollellO in these states *ere the lemma are small would be considerable.

Complete data on the total diversions by all eabala in the Wester* States are not reported by the Census Aureau, but the total deliveries to Weer*, based as meaaved and estimated quantities, are given in the irrigates reports* The date for 2939 are set set in Table 1, together

with the total losses imputed from the relation between the quantity of water diverted per awe to that delivered to the farmer. The total loss derived to. this manner, althougji admittedly only OA approximations

la morwoo

asro..foot per annem4 er 38 persona of all eater diverted.

Pert of the loss is due to evaperatioal lollop from faulty struetures and. laseeurate sounweasat of Oliva**, beirrerr atoms probably eauees a pester loss than all the Ober* eeibiesd• Meet of the water lost seeps downward and finally beeomes a part of the ground ester

ahich may reappear in the streams se return flow or mey be reeevered by peapiai fret polls, but some of it is lost to the drainage basin

by

aigrotioa to othor Udall so mom la Mt* Platte Valley, %ad sow. atiofthilo pertioa osommalotos La water4oggia 4,0141frmwhiOa It Ss

disotpotod evaperaties owl tratatipiri,tioo• Th. lagRite40 at **Oh of thoo0 qamatitLos somot be 4totormiao4s but tho isportanca of ti losses rrom *awls is uppAroat free these figure**

ractort; kftecting 3**".

Seopaga is caoteaatily dorined as Wit emerges.. of **tar from matorktvad $01.1 ,owS.aps the disappooroboe of water into tho

Aeeoraug (12)oettiwite 12$ the swoliQoat tor **tor into or out 1St the wood, k simil.r wofiuttiUms Lo lavou Aelhuertl, tut for

asmosiotb.lowhotStwoos IstrooltAien aiaoltlehatsiatt***ou4 in ute woetteteAvei somas of oevonens of looter ta oatur*A44 ao4I40 IL thia ',port **opts* to *sod to rotor to tho aoroewout a W4i4V luto 4r out

of irritation eksangs thrtAidit the hot aotorioa.lb. sootiat Otoieptikige

Hwy biwctsered La out* ieet pew iNuaros foot of outer Kitts** or of mettod ourrAvt, Nat *4hoarti, nto

robot

per twom4 pot .11* or ta pwrooat or total flee par alto, Of thews tome tr41bt:! twit per *weave root 0C lettet evertoeo pow 24 Wura iv believed bo b* moat soaertaly mega. It is tiger mLt adopted fiar till.* Mori*

AISPAls is 01011401 hY414441,4* Phalle*** Mei boosek* or tas otsny toriolotoo avo1d 010000.4.. * sevot&as las rut* of

41044),-.4.1 4‘0 boss Asvolpepod* Moo aster 14 flowtag

in A

(wail the water

ip ootit4.4t wittik the bottom and the banks of th* 4iitonel isoodiatiki *Ur** to moms tete the tatoratioos totem* the pfirtio1os attlidag op

tb* listing of th* *LAtinslo

rm.& worimuset

1,4 a oombins,tion of capillary

.

011k.

attraction of the fins passages batmen the particles of the ':41.1 saterial *wrests poreolatiea is sassed by the motion of gravity la fereiag the water thrash the peas of the bed asterial• The action

of gravity is slays demeard he *willowy stir/Letts* operates in all direetions end fray same the water to rise at feet above the level of the water is the ehamme3.0 Capillary movement is extrewely slow and for this resole it is ordineril; moll Sn easparisen with percolation.

The llama tanks and hettam is contest with the water are always attested, 1.14 a the water seoplag tree the anal leaves this sans, this us, army not be twos. If the eater table in the area is In

above it

contest with the bottom of the anal or has risen then all the soil in the imeediate vicinity of the eaml below this lora is saturated,

and the seepage follows the laws of persolatioie• If the water table Is above the level of the mar in the eastals then the direetion at

floe tevard the easel and a gain in later will coeur.If, however, the water table is loaloo the level of the bottom of the easel, the region inemitately toiler the owl will not he saturated eneept in speetal

eases, soh es *boa the imadWhytes esterial is less pervious *Math, bed of the shassel. lbws this moire a pressure sans is Wilt up erased the lotted peptise, or the Eiduinsel and the floe News as

per-alation, Gemsra,Uy, homer, whew the ester table is Woe the bottom at the emeal„ the ester seeping from the anal flow demeard by gravity as e Wm of water &lawmaking the particles of the poll. Under these

oirowastaneee, the later lost from the anal flows downward in a am direetly beneath the email with little, if say, lateral spresding• • Perociletion (laminar flow) is the slow meesmonst of water is inters,

**mooted pores of saturated granular mattrkle under )ydros/le grodients ematon4 developed urtdergrooted*""

Thelmossability* of the material forming the lining of the easel. whether it in the natural soil or an artifiaial UMW* is in gement the newt Important faster in &manias( the rate of seepage. Perms* batty is Influenced by the sine of the pores and the pereentsge at pore spase er porosity of the material. For a given sta. at pores, the

permeability inereasea with the perseity, but materials swab as *lay him a high porosity are relatively impermeable. This results from the feet that permeability also varies roughly

41

the square at the diameter of the pore spaees(12 P'45), and

AMMO

Ia. clay the peso

spans are lismismall, the parmosbility is small in spits of the high porosity. the presemes it grmesl in not materials decreases the pier. mmebility beams, it redness the porosiv• Gravel alone, it maido sip at partieles of miter' aims, has a high permeabilitybeeense the istero sties* between the partieles are at filled with flaw imatorial, and consequently the pore spaces are relatively large. Soils mode up

at

grovel ins matrix of slay are practical)* impervious to water And ors quite stable.

Aoserding to Darces (1) low, the nileeitY of Mow lihnlab water" bearing sands is directly proportion' to the hood sememmed. This ler is generally assumed to apply to all saturated vetermobearlig materially in shish the pores are of capillary else and the flow is lemilmere 1Spertmemts at the Welled* Isheratery of the Goologisal Sorvey dhow that simples of soars* gravel ow triumph ester at a rate 0400000,001 times that it elayey sill(14 1411)4, fhe porosity eV*

'Ism silt los

Se poviemt and that of the gravel 38 percent. Pee a heed

at

one feet • Permeability

mow*

vied is the eapasity for transmitting later

•

per fa* of this gravel, the disabuse was 90,000 tallow per square foot of eroes.seetieeal area per 24 boom Under similar ',auditions the discharge through the clam silt was only 0.0001

mum

per 24 hours. The wide range at possible seepage is apparent from these figures. The actual losses free 'analog however, *re fir less than the maxima, beamse the bed materials at canals are partially wooled by silt and clay carried in the water. Fla-therms, although the depth of water in oarels may be as great as 5 feet and assetimes even mere, field studies skew (see page 48) that the seepage is ealy leeway serrelated with the 410114, This leak of eorrelatien bats.** depth and rate et seepage has teem reported also by Laas(22 P443). In a stud,'at eater spreadiag for storage underground, bitobelson° 148°) observed that the seepage rats deereeeed saterial4 whoa the water table reached the level of the water spreediag ground, but the depth to ground ester hed me effect so long as the water teble was baler the surf** et the ground. Maximo seepage rates essurred daring the period that the water table was dropping atter it had risen to the ground level. This effect disappears hesever, what the grewmdimater level has dropped several feet. The eastoinatiot St these factors, together with others, the inflame of WWII is not recognised at tho present time, makes it difficult to evaluate the inflames of depth of eater on seepage.

Seepage is ales

sfriatei Iv

the temperature of tile 'stir. Aeaordiag to Foleeuillea(1°) law, the vileulAr ef a liquid through a eapillary tubs varies directly with the specific gravity of the liquid, the head and the square of the diameter of the tube, but iumersely with the

wiseeeilw of the liquid. Since the viscosity distresses as the tempereture

44*

Insreases, seepage Should imeroass as the water grows warmer. fir ordinary temperature ranges the eoefficient of viseeeity Changes ablest one waist per degree Fahrenheit(2 14209). A similar shimge ahead be expeeted in the gnome for eads degree Oens in teispereture of the latter. Although it is generally assepted that an appeolabIe shamp is the seeps ago should tabe plasm, actual seepage measurements Level:se se nany unesew Watts' that it is rarely possible to differentia** between the effects of the various factors, (see page 48).

The theoretisal relation between the various factors and the seem* according to Serey's law(14 Pal), is expressed,* the formula Q it

is Q is the quantil, easter in vat time,

Le is the eoofficient of itydraolic permeability, (the subs script d is used here to differentiate the Darer coefficient from other values et 1 appearing in this report),

Is the hydraulic gradient, mod

A Is the sett*d area at the eamel bed and beaks.

This formula may oleo be expressed in terms of the heed evellehle as Q *

In thigh 4, Id slid A hem the same missifisaase as Wars. h is the head 41111110011111111001.11010

* The seeffloient of permeability of a, material ea defined Itylleiumer (11 pe148), is the rate of flow insatiate a dey thremgh a squire

foot of its crosesseetion, under a hydrofoils gradient et 100 proem*, at a temperature of 600 F. Other investIgatars haves defined the soefficient in terms of cubic feet per day. 'hen the permeability is extremely mall, the 00effic/o0 maybe expressed in gallows or cubit, feet per year. IsreelsenW has suggested a different ;waffle-lest Us *Joh he calls the specific) motor conductivity and defines ass 'Ti. vulume of waVsr that will flow in unit time thrs soil *Alum of limit oreasseeetion area due to the drivimg foram per unit mass correapesding to unit potential gradient", Ihiobsver seefficient is adopted, it Assad be mated that this determines the unit in whisk Q in Darcy. s law east be expressed,

pedaling sumo. sAd 1 Is ttre length of the column of material through shieh **pogo is Wing place under the head, h. All these variablee are readily susceptible of direst seas _resent in seepage experiaento ozoopt 1144 the permosbility, and 4 the hydraulic gradient. &morel formulas have been doveloped by moans of vhiah E4 ma be somputed from the temperature or vissosity of the meter, the porosity and the moohsmisel analysis of the sand. none of these formulas have been found. entirely satisfactory. Permeability may also be determined by direst moissuresent of the nos by means sepaseemosterst by msaraverant of

velmeity of nee with dyes or obsmiools, or by esmputat4Ass hem the draw-doom sod diesharge data from ploped malls(15). The lastoommed. method

has the advanteipiat givimg amswerege valve for the matsr.bearing material Is the region of *sometime molls.

The problem is eemplleated still taw**,

by

the fast that the material asmprteing the bed eta ehamnal is not unifonsi and the pormosm. Malty detorainni tor a sample of She bed Wren at one plass mey or may sot apply at am, ether pion. Also, the permeability usasurement* should, be mode as undistimstmodismAorials humus* marked obanges in the *traitors of the material usually result it the owl* is brakes up and then rogo peaked for testing. For this reason it is desirable to asks the test in plasm I: possible.

Difficulties are also encountered in deterinim this *Motive hood eausimg the soopogo from canals bemuse of the groat variation is

sonditions. Tin depth In the *anal is only one se the bottom* Aoloordial to Derses law the pressure atbeth sods

et

the esaina *Mei Ad*

•100.

must be known before the offeetime b 0113% be ditessissed. Insourement

Of the arse throseti eilielt seepage is taking Awe presoak as dittisaity• Meet eanala are of 'fairly uniform sorties aid a few prattles sows the canal will is a ressonahly close approximation of the area, There the lama le irregular* safTinient escuraey ea* be obtained by taking sore

predilesi

liseause at the aft leultiIa asemering the parimeterei ilareyss formals s cannot be used is ditemmimimg the setwa eeepese trem a await but it is very useful maissieteeding the relatienabip between the wartstus factors end the esegsgsto Ellen thee.* the vans Of 54 the coeffieient of sisermeability or of X. the steps, may be Andenews, it is rie0114 apparent free the fermis the, the seepage is directly pryer,

Weal le *soh of these testers and any *asps in them will affeet the seepage in like proportion. This is true also of the area A.

Methods Of Measuring Seepage

Ulm* ameamrements ea easals mey he divided Late two el/mess theme eats sa a relatively isms ~atm of the swat awl these sale as a wattle portion of the eamal bed or as material Arms skee er mere

paints in the eanal with the thought that these aeasurnmeats mad be repreeentative of the whole easel* latier sag eattlem measurements for the seetion under test and sinkage measeremsats ea a peel towed in

the smitten are of the first type. %movement of seepage bun pitons the sena or in material similar to that is the earalso and iteasarmeeet of flow through undisturbed Interim' front the sane" led by *sans Of permessetera are of the eseond type. Measurements of the first tope

sosioellived to be,mait mere satisfastory than those of the 'mooed typo, although, it is reaiised that nos of the methods are withset detests*

Inflow and Outflow Neasovneents

Ikon the inflow and outflow method is used, the quantity of water ealterimg the motion and the GAM* must be esouratiC464ermined, together with all leaks" Aserements and diversions* If the mope. leases are small, ocuperation and precipitation east also be taw into sonsideratisee -Changes Luba* aid shaneel storage due to riming Cr telling stages of the easel have an important effect on the glikatiV leaving the scatiom being tested* end nowt nil be meglseted ifassurate results are to be shiaised• lessuse of the warrotbdole ineemoresies in the methods of amasuring newt% water, it is important that the section of the easel ahem for testing be as lemg es possible. Other. wise, the errors is moaserement any be greater than the mops. less.

Vim simp1es6 kind of seepage awasuremami the istlessioutflow method owlets of single determimatioas of the tenser and outflow daring a time iiihea the stags of the emmd is constant, If the seepage loss is large sad the

MOW

alialaareilkiete are oarefully made, this method may give results of reffisient aseursey• ismally, however, better results will be obtained it several neaswrimemts ere token at *ea sad of the motion being tested end the avirlaSam mad is aaarattait the 1•111. If the seems Imes is milli oven them* sere istummtia *shim the nesserememle, the dillaronses in flow mg isdisate a gain when this althea As med.

42*

Mare esearite results will be obtained if the Wtal lifle, sad out..., flew aver a period of days to detereined. To do this, ester stage recorders ore installed in the *anal et the *ads of the sestism, being tooted* ay seeeering the floe atom/ station throughout the of SUP if the esmal, Umberp serves tor the stations ere dotoreteste Me thee, data the total inflow and outflow ewer

for

period derieg the tort ago be reedi4 eospeted. If the period Is ahem* ea that the Ono if the oval at the besioniN; aod end of the Interval is the same then the different* between the total Wise end outflow will be the set left. It there is edifferetios is stage, * wrestle* at be sole for oitameol stems' The difference, when oarreetod tor imreperatioN pre* oipitstless leeks sad divrreioes wilt give the seepage loss.

there are several eethods

ayr

ehleh the flow in, the *anal tea be measured, but ender most eo4itiono1 the current setae astbed is the swot preetienble4 Where there aro weirs at the ends of the anti** sr ifthere are &mks *so* weirs 'subs installed, their us* will he it possible Uptown" eseersto Alseherge measurements* Is most

instaaase, hoover, there is sot sufficient fall in the *seal to install mire sad ter WWI room ourrent meters are severally used. The gm*, stations at which the surreet War siossaments are to be mode 'heal he &own where the esossoseeties 4 the shoonel is sell detbasi

preterebir las limed metier' se that the ttlasseelooe oso be saeurstel, eseserodo The statist Amid he free free ebstruotiees ebieh souse disturbances in the eater and the veleolty Should preforsbly be betimes 2 sad 6 feet per second and as near the same at the tee stations as Posatbis•

MI\L

Air staciard _{seadititea and assunitsly salibrated} vow he wed 10 _{sift the mosseisseilists The ist*Oretthe method fa test} ~ea Usemmis sad laterals and the twoosadotight. loath* method is ressmesnisd tor the larger esnalso The sultipla point mathei soy sine he. used is sesseriag large easels het errors asrhe istredesed eaves to &sip _{is stage et the emit beeause st the edoW}

Weal tism sewpstred to *ft the asasiromeest• The six..trfuths settied is reeeemesded ter shallow savalso but it is doubtful whether this asthed is assure* sus* _{tor 110110p00 loss deterefinations maless the losses IMO}

7 large. whigthever austhod is beim used. it is essential that a WA.be Pnreidked tor the sest• seasereneste are toe sehjoit IA ewer fay this type at cot, _{sem motor Medd peettoratir be} used ter both istbe _{sad outflow lassimmakr4s as this pressearo Wats} to sliminnte swam in salibratioa of ia *Ws. soisirsossilo tit to _{ditterest types fit asters are *Wad& boom srorsilsi the} romalts helps to eliminate the West _{atpossliarittos at sitber ortim.}

seepeis detomeicatinas with s isarem* otters the assures, at the ~at _{is governed INT the nature at the Orme in the sessireseniso}

sad aro respostiisky the troe Una" and extries0 and za, and at Lbs sorresperodise error* in meastuiseat expressed as reties5 whisk say boo atm. _{pesittv* ar sooktpivo. thins Os taw loss Lsq and} the masseved Use is

h (lt ria,) * 02). The differ.ass lotuses the true and asseersd Ism is

Hondo it the errer in both assumements is the same, iseit if et h

•

q2

there is no error in the result. If the persert of error is the same in both measurements them

al • 112 n and. al Ql ! 12

412 •

_{eaCirm‘42),}

er the permit et error in the result is the somme as the person% of error Lathe asasereleatait and slam the persest of error in the measurements is small It will be small in the result. If the values at 4 differ bath in magnitude and itigot then

; 41 2 142 teases X /II A X ei 42.

The error in the milt is the svm of the setae& orrerai in the measurements *doh may easily emseed the lees and depesdleg lathe Aga MI either

materially imassise the meammred less or Shangs it to a gmla.

Pomo the tericsdag ammlyele it is evident that a spesiel attempt most be as to have the errors the same in sign and equal in magnituds* It is for this names that both the inflow and outflow meoeuresents should ke made by the ease observer; that simile: gaging stations be shown for the inflow and outflow measurements; that **Otiose with large diversions be avoldedimilthiht the sem. meter *ad SSW MAW be vsed ehareverpeesible. Under the meet favorable sonditions, smiemperismeed hydregmaphor should he able to make pelage inkshieh the error La the diseharge Si as small as ems preset. Generally, however, met ell eonditlees are tamable, and when this occurs, errors of tee pereent

or larger samreasenahly be expeeted.

Leah,. through street/miss and diversions tree the sanal ammo* be datormined with a current meter with suftleient aecuraey. Small leaks eon usually be measured most satisfactorily

*

mime of it

60. degree triangular weir and diversion* OM ha measured most easily and

•45di

met acaurateir

*mans

of reetangular imam Ur, well lake cs* msmally be estimated with suffisiest semersey, but shore the seepage knows ere smell, as fres limed *anal*, the smell leaks have te be measured aoswtately. Voluemottio sesaaerioftne are most satisfactory for theme small floes.

The effect of precipitation and evaporation is relatively small sad tir that reason these quaatitioi inn be obtaimid fres the raga caught in any straight*sided san and the evaporation frowsier. Osik smgponded in the eaoml. Evaporation moescred in this maw Is aft the tree eisperstiom from the canal surfs", but eves a relatively largo error lathe eispiratien mill have very little effect on the ascuregy

at the **PIP iliamusement Weave* evaporation is an insiemitisait port of the less essept 1* the tightest lined. °anal** For most mops. meauremeate published date an evaperotioata4mrs sufficientlyikicateto.

Zr thus is an appreciable *kap in the stage of the canal dual( the time that seepage measuresents are being node

kf

single measurements et the inflow amd the outfit/40 the reemIts 'ill be uncertain, but when the esepoge is being determined lw the total below sad outflow over a pod* the effect of any different* in stage betweem the hOogiamisi sad end of the peeled eau be eliminated bar 'cavorting the UMW* Mange into the inflow or outflow in outdm toot per second amesseary to prelims* the *haw in the elapsed period of time. The velem Shoo 'Mho the

•

Pits end Piles

A simple method of estimative the seepage that will seem trot a new or proposed easel is to nets the rate at shieh water drop* la a pit lbw lathe soil adjutant to the oanal• the pit is the sane dip* as the saga and is kept filled with water until a stable eondition is established in this soil surrounding the pit, the rite of seepage will booms peastioally ~tent and will roaghly approximate the lees frost the easselo The rate will net be the sam as that fro* the **sal beams the lateral iesosesst of the ester tbee* the seal is less restrieted is the Pit than in the oisinal• ($50 PIP 37) ?his method also, doss sot take into assowit the attest of silt deposits in the easal• The seepage fres the wool asii swoosh bat will robably siver instead the loss from

the pit. Data obtained in this mow are of United seiestitis vsbas lad they provide a mesas of sobs at Imo* reasonable essesptiese se to the Jams fres new or proposed easels*

Probably tboamiteeourate method of meastiriag the seem* less from meals is b7 chg.-Twine the rate or drop in 41, pool formed tramming both sods oft seetion of the canal. The only Objection to this teethed ie that the asepsis rate nay be different in still water then it is in nada. mater. Missower, it there is a differs's'. it is probably small in essparisoa with the umsereidable errors with iblek the engineer is entreated 'has sakisi seepage diotalibutice ireo Gear motbodea *boa this method is woods the log* of amnia* nay be short or losig deposding Osallitions beanie this less* deo not affect the soeuragy et the resets as %hen the less is nesiored lOy the mama nets, 111.thelie Zngeserel, the grade CC the easel will ideteesine the length of the soots* *ism

Siam the water in U. pool will be level, the depth at the upper end Will &peed Oa Ike length of the seeties and the grads of the 'anal and

U the emotion is too long there sill be 'considerable difference in the depth of water free one end to the ether as well as in the width of the

water aortae* sad in the temperature of the water* Thom irtirlAtiOrkii

he it diffieult to determine the true aespege*

A saatiem between tee *beaks in the easel makes a saticfeetery pee3. boa boosigo *Wks are usually met water tight it is aeoessary to Um* earth against then in order to be sure that there is no leakage. Oewallipi Weever, it is nifillearr to build earth Elaso at embed of the peel

beaus. Sheiks or gate. are not available tier* seeded lathe speties is be tested.

The rate of drop in the pole sea but be soutrodi Vans* at males or hook gages attashed te steles aitvea is the oanil is kg, plefibsobOb Mee shish amours the di/tame tether ester aortae* tron ininnt,sinta *stabs.

limbed on bridges err other struetures* Demme wind nay cense the water

to pile up in one end at the pool* at least two gages should be used, pretwriehly at the ends et the peel* The ansher of obeerwatione each der

will dopoollse the nut of loos Om Use peel. ordigarily Instises easi or Wise doily will be entrieiento but it the soma is seeping away

it

twr

be neeeseary to teak* hourly obeerwatiesmo The time of flub shosruatica should be meted* iseanis the seepage rate shows with timmothe asseure. seats sheuldbe wade after the ossa bus been carrying water long enough

to stabilise ocaditleme* It the *anal has not bean used resently it Should be kept filled for a day or mere bete, Siertieg the ebeereatione* Gains or looms from precipitation, inraporatiek aM leas should be

The principal advantage of this method is that it is passible to determine small losses such sore securetely than by the infloopoutflee *Abode, By Isaithealm, the time between observatiens the drop lathe eater surfaas sin be busressed mail it is large oneesh UP he meamared

without appreciable error sad this ems be shoe without introdesing mew errors. Depth measurenents ems be as& seek sore sommtely than die. sharp seaseraments sad they are also mg easier to make. It shaeld sot be isterred that seepage asaatressirts on pools are tree free errors. Sesults frequently dust sonsiderable variation, but moth larp dimmer swims as are one* feeed in the losses detereined by the intlem•outflos

method are selAsso if over. emsematered• Permeemeters

Various types of peresameters have been developed for measuring the permeability at soils lathe laboratory, but most of these devices are not suitable ter emosuring the neiliplip free osaila beeases the eenettiees are not the somo• The *Mao esseist of a cylinder filled with

the

soil to be tested. a *apply reserteir *Lek is essmotked 4th eme end of the cylivier so that the praiser* developed eausee the atter to porimplate the Os soil, and a reseipimela fee' sateddag tale UMW that piinvin threigh the sell. degas are proviAed tor sesserisi the voter pressurs as each and it the sempla• The eeeffiaient at p•rawabilityis compatod from the lemgth sad cresrossoties fifths apple, the diaeresis, in head,

the quantity of water passim( through, the temperature5 and the time.

since the ermeability is affected by the arrangement of the sell particles, It is important that an undisturbed sample of the soil be used invoking

••19..

sena beds beam* _{the eater 'ferried wally deposits a leyer of impervious} silt 'or clay lathe small* Woes this layer remains intent lathe sample being tested, the Observations an permeability sill be erroneous. To determime the seepage foes the esnal the pressure gradient in the tonal suet be knees as well as the pmemimaldlitateceffieient Whinh is based on unit heed end gait less* of emerie.• leenuee the preseure varies trma point to point in the easel bed, meemorememb of the pressure media* to seldom attempted. The computation of seepage is based oaths measured oestfledent of peresibility ant on assimptlem es to the presoure gradient* Seepage determined tir this method is Obviously of masertaial value*

Another eetbod otdeterminimg the seepage with a pormeametor is to install the parameter (see lion 1) in the bed of the emit sad then similmre the 0,01141, alret the peneeneter while the weber is Lathe easel* The drop in the Niter level lath* perimempieft the time and_the keel with rellmvenee to the ester level in the ems& ese observed end plotted. From the sine twin tbreegh the plotted petats, the someteste of the general permeameter equations (see pew 2$ seats determined* The solution of these equations for the eamditiems *so the eater level in the permesmeter is the sem es the eater level in the °anal gives the rate of seepage through the bed it the eamal. Although preliminary experiments with this permeemeter yielded inionsistiont results, it is believed Shot this devise has merite

A ami device of We Vpill(5) has weeently bees developed ithiek emseures direotly the seepage that is elosurriag through the mama bed under the

eifieditleas axieties et the time. This devise somodsts of mi cylinder apes at the bottom, *doh is premed into the samel bed end a flexible rubber

•

Hook gage le Z H Datum

•

Water surface in measuring cup Petcock

Elevation of zero seep Garden hose

Water surface In canal

?Igor. 4Pk 64mtion of oftwals sulo rommoster *basin WV it

to tostollad in * samo140 As impremposit ta •4600 *WA

be

top mks

this top at Os wimp _{000P immiciao}

-20.

reservoirs which is atteshod to the top at the eylinder bromism, of a hose, (ass figure 2)* Ibie robber reeervote is kept submerged in the *anal so that the proinire imam Seopese throlik 000 soil In the srlisder is the same as that oaths samal bed* Tiee loss is determined by raising the rubber reservoir shove the water surface amOlthen weighiog it, trot the elapsed time *ad the eres st the celinder the seepsjs ean readily be determisod* This 'Wise spans to have eiseiderehle aseit Ned it le hoped, that sufficient comparattes data will be evailiblo Sven vs that it will be possible to tell whether the result* obtained are sufficiently

reliable Ale general use is motoortad 004111160 1060084

The variable bead pernpaseter is a device of this type adapted to the neastlrement of the permeability at war: tight soils* It eon/gate of a sylinder with a conical top to whisk Is attadhed a vertisal glass tube St small dismobsr* The cylinder is pressed into the soil tea hams depth and then the Whole apparatus is filled with water* As the intim seeps

three the di* at soil in the cylinder the water in the glass tubs

dispo.

Aimee the gamier is usually asis with an area 100 or acre times that et the glass *Oh* a email mount et sloop registers us taro drip in the glass ties* Iftpemmashility ean be somputed frau the Initial and reading ot the heed in the lass tubs 011.412), the time interval (T), the thiamine of the soil disk in the sylinder and the ratio of the ere* et the glass tuba to that of the sylinder _A

The fessals is

_h

I • _{2•3 AT 31410 bit}

This variable bend pereeeseter has been vested

lir

the Utah Agri* cultural Ikreviment 3tstion(5) and wee found to be effective in measuring the permeability of very tight soils* The principal difficulty eneountered

•

Scale for weighing water in bag

Water inlet

(Hose filling Water inlet

Valve for air outlet

tWater surface

connection for bag

Canal bed; 12"

ELEVATION AND SECTION

Seepage cup

Figure 2.. Perseamoter developed by Salinity

Laborutory at Riveraido, California,

.is the tiewlewey of the cylinder to lift hums* at the presser* alerted the leeide at the eylisder by the colais at rater in the glass tubs. To owereeme this teademey * lead was plead ea top of the cyllider.

The testable heed poraemmeter measures the pereeshility het set the seepage rate. la order ***Ansi= the seepage it is neeessOPY to know the hydraulic gradient at the flow through the *ail bed* This typo of persammiter is suitable for compering the permeability of different sells for nee in esnal lining. The perweamatere previous* deseribed are better adopted to sosouring the actual seepage fres canals. Serrirer, until more data are available as to the eccuracy of ikon devises, the most eertain method of ebtaimiag reliable aespose records is to build a pool in the section at the tans' to be tested.

Isperizassiel Date

The experimental data for this report sere obtained fres tests made in Californi* and enlorolle am Ammo loom boo Used and unlined

easels aull laterals* Ohsereatises weft else semis ea the looms tram pits and trellebea, the wee of pormisairtOn in meassring ammo no investigated in atteeptiog to find s staple and accurst* soothed of deter* mining the amount of the seepage loss and where it was occurring. In asking the mopsge masureeeste as seaele and laterals, the less was detereieed oithor airtime the drop at the eater surfs la a peg la the channel or by aeasariag the lanes and male/ Ow a softies at the channel with a onnrostooter. Mere it *as deemed advisable, Wrings were soda aloft lines paripereelar to the ehameels to get Jeanette* ter preparing growedwpater prattles* The melts of these iniestigatisme are presented la the follcalag pews.

4400,

Sispeipp*O" tssvalasster Ilipostasols

Seeps. bee len sestione of easel *ere the lasses are hiab sum

In determined 'with reseconabilly seetreiey 1140.33$ of current aster $6111.ormei

sent* and the seepage from abort _{sections of °anal can be determined}

with precision kr aseetavasmit at the rote of drop is pools anie is tight soils. Roomer, when gemming to line a easel it to

knew definitehr share the swage La assuming and for this reason it would be desirable it Aires* measurement of the rate of seems could be made at any point of the bed or sides at the channel. *either et the metheds jest somtioned is suitable for the purpose. The peMmesmeter refined SO empage

la

*at Shown in figure 1 was developed to assoori seepage under these eanditiens.

hs Ahem in figure 1 this &via consists of a cylindries1 beIl hereafter referred to as the mopeip cap, libteh is reread late bed or side of the @anal sad a smaller cylindrical sup, which is attashed to a stake driven into the camel book in sneb a manner that the sup will be partially salmemrsedo Ahem sesaasts the bottom or the small emp with the 14p at the seeps. OW, A be* pp for reeding the eater level La the small cup and lathe easel is fastened to the Asko drives into the wad bask* The letter reading is Obteisedbyepoeiss the's*** lathe sup sot oUseing eater from the simel to enter. A *teeth is OdiWise to. 460 top at the soopego imp to *Win ail/rapped air to seespo• The itasetesk at mosli op ahead is *We fres 1.6 to 140 of list it Abe seepage sup la miler to tespdry the areaway as that O. rate

eau be nor* soouratoly toossorod. In the equipment Sheen La figure lo the ratio of the diameters was 1 to 6.0 the area of the small eup being

4,234.

04C129, Wore feet and she area of the seeps. sop 0.5675 square test. Asaresult the ruts etdrepiemessified approniaately 44

To dotards* the moms fres* easel the elopegs sop should be *Irefully fora* into the bed at the eanal at the pods* awes as Vast the attorlol will be disturbed as little as poesible• Mese *tight seal mot be noluteined .lo wg the veils or the sup, it shoeSA be termed straight down into the bed and preferably &load be allowed to stand loss enough far disturbed satorial to settle bask into plass* Ail air

Should be driven out of the mope. op before foreieg it into the body laverting it *dm, water, OWN the seepage sop he. been firmly seated the Mee whisk he. sreviously boon filled with ester should be ettelhed as shown La nor* l• The Woe* *eat be elseed as Does as the hose hail been attached tat OM air that say have aseumpilated has

been allowed to escape* If all the eennestieme are tight, the level in the sop should begin to drop imse415te40 It it does not drop Ws. the level of the eater in the easels leeks Amid be suspeeteds Seehage is moot Moly to take plass under the lip of the eeepege cop soll 161111 this oesurs *ireful tamping *ream* the *Ides will, semealy ma small leeks* It the leak omit be stopped, the mop should be reset.

To determine the seepage nit., the aster level in the easel is mieswed oat thea War is oiadoil to the smell sup until the dor* to about OA test Owe the eater leeel in the easel* The eater level Is veal and the rate at deep is earefully measured by Observing the

Wood* a stop watch, required for the level to drop definite distasees„ memally 001 toot or lees, until a level is reached beyond *Job the

water will not hal. This is the elevation of sera poppy At this I.,.] the formes sessing seepage from the /sup are belesmosd by the

ow24a,

tams from outside the sup tendi ye water into it. After this level is reached, the rotes* es the sop Should he opened sag the slave-tie* of the loiter in the email $ods deteemiaed•

The 0140p11. throe* the area laelesed b the seepage rap aMems. eloquently the rate of drop in the small sew deereasee as the eleval

above the ester sorbss in the sena deareasee• lit is stiont to the seepage from the soma, when the water in the smell cup is at the seen 1001

as that in the *anal beeause the water preslure on the eanal bed inside the seems sup is than the ems es that outside.

This rate MS be feud grsiphimaIli

by

_{*empties the aversgi slosPege} rate Wm** sasseseive depths lathe *up and then plotting those values eSsiinet the NM gag* Man devise the interval. The our,* dress through these stets gives the seeme rate for as, gags reading WAILS the Units severed. The value takes Irma the owns at the goy. readies of the Leval of the later in the soma is the sespege, lisssvor. it the level et the 'meal rose or fell during the pried at the test, the point 'here the level in the esp log in the **nal were the some oam be found tff plotting the gage reeding In the sop and the gage readings is the easel egelast time. now the re/rating flume interim* is the desired gigs height.

The 1000040 rate *an also be eeepated fermis* derived from the theorotioal relations between disebtaie, perseabilUy sad heed,

Aeimarding tO Darerto las Q * A 11 (11010 pegs 11). In the ISM et the 0114010.00 sop wmemaster, h (11.44 whoa 1 elevation et voter is small OW ebb reteremes to kook gigs at** and a I elevatiom ed IONANO seep seasered from Use same down (sea Mpg* 14* The length of the

edam of material la thros# Oda sespow is ssourrinit is equal to the depth of penetration at the seeps op into the hod of the *ma* It these 11111111111111 are evitstitsted in Darcy s ferrule, then

Q • YAW 1

This area of the portion of the bed of the sisal es* tir Idis mepe. imp which is the sumo as A in Barges tareadadi IS IP is sebeitits1011 far Al then

* (WO ad

Us nee isestrisisat Iis isalmotilitited tor If a

*11(11•4)• (3.)

The drop is the later surfs.* la Os small sep in ties di i.e and sines the arse is A.

Q " 4 hitiw (2)

Singe Q is the ease in formals& (1) stud (2)

e

• It (B.").,

sonditioas Sion the elerwatton of the water guess's Z In the canal remains cw;stant as the olewatica of sere seep is a constant alid by integrating

X (110.) the Amide

44 243a) t Cleft:pee) • left (ii-sbal) Li eloteinet, Thee if Zs to substituted ter 2.303 t

goo s 2 303 it

iiiiimpaitemrhowaimodoml.

See notation peso for list of *Abele Milt definiti****

4160 and

E

14g10(3io 11) 144111041)3 The formula R SP as • a ICAlga (5)

is Obtained by solving roma* CO fer 1. Differentiating (5) Ilia resat to $ give.

it • ide 000 * LIU ₍₆₎ 3.0 As

If tei equals 1/2 tra ssIs is the aseresporxiing value of Ri %boa tram equation (it) it GSA be *bona that As• a) ii * assa pevportional between (110 • a) and Oa a) and limmratera

Isilevise, if the final values ton and lin of t and 1 are selintitutad is *patios (A) end the resulting equation is solved for X.

• tiA utisur(a.

-* m)

The relation obtained by substituting the vases of a and Is

momPutod from (7) end (41) in CO is the equation of the curve passing through the initial, final and nid..point of the aim of observations*

emilkinlas equations (2) sat (4) _{and makintitutieg for II it*} value l ipidon the eater in the cup Is the um almatioa as that is the *anal. the sable feet lose from the cop per 24 boors is

24,30 if q^P4293 X 86400 (Vita) is ani.i 000 (9)

AO

where 041293 is the are* of the wall cup is square feet and WOO is the maim at sessalle In a dew. The lees iseubie feet per square

feK4 per 24 hours thrvugh the disk inside the leepsge eup is this

Gs gandi $ 4534 064..a.

0.505 (Itid Is

whey* 0.567$ is the MVOS of the oeepage cup in square feet and Qs is

U. seepage in *Ole fest per square foot per 24 hours,

To impute the seepage iv equation OM it le

siatonuary

to detente*

so the elalistiee of owe Seepj experineatalir la the field

a.

14,

snip.

stituties .1611104,414 'Slain* of It in equation (7) ail otter a bail bona

tee*

to

eta be ditiereined tor

talviss

aquatics 00 • ageatise

• derived is the assuiptiae that the eater Leta Le the easel las

~teat end tar this eeeditiee a is the heek gay

reettage

UM

the eater level in the *anal is risieg or falls* elate the

ebsereatiees on Us Aiwao ow, are being ado, thee the elevaties of

sere seep else varies* Spode% svattiosis met belertsed to find the

seems woke these eeedittees• nese seepage sap ebeereatiees sheeld

set be

soft

mart Asen the canal Mose is reasonably corm 'ant to

simplify the derivation of the tamale a unifort change of stage is

*saes* to take plows betuesn the initial and the final he gap

resdieg of the ester 10,44 The elevation at sere seep Mama

the

thaws in the water surfed* at U. 111101l. lad is

As*

010.111ed to *Opp

at a unite= rate uhieh is the OM an that

seemel

fcr the eing•

Oa this sasnoptise. if aoaM s. •x* respeetimar the initial

elowittiene et sere is and the attar surfs** in the eanal. and •

the rata of

*mpg thee et ex"

tins t

a s ao •

et

*ad

The *pattern asernapary I.dietevatae ISO seepap toga the eipivt mentel date eta the* to &rival in a swum sladler to that proviouolly

intplainede

It - tio -A Isom

e:714 1,041 40 if 0 4/13

*en • atr0.434e1ts (12)

1(a•0) * A 52•303 11° 41 I ob ;3

03)

N • g • *to tram equation (11)* (U)

10 As

Ittrfelrentisting (14) with reopeot to t shoo ow IP*

(

s

f. it 2.303 ( (jet° 0$ 243211, (Hfiarei) • (2) all

When tit 11 ts ib els le * seas prepertleal between 11. ars g • Pres *blab

I *

MA-7-312*

ae.ieltala

•

2

(Rena)

*

ete

RoiNvalia

eta

It ba la sigiatituted for h and. ta for t in oquatioa

(U)

and

the equation Is than solved tor to

Ito $

t

101010410 • ioitalterots)

47)

By aultiplying *pant* (23)117 A *Ad exibatitut:- ag Z a zo at for R Ott. ft. per 24 hr• tras ettp • WWI (Zeit) LW. (1A)

Is

29.

TO save equation (19) tor Qs the seepage rata, g le *tatted trek (16), Z fret (17) and s is onapeimii tram the initial sad nail value etZ sad the time Mom the astir level la the eemel

~taut e golpSLIS *era. Ny euhatitoting sore far oi la the equatione 41110410d ter varyiag easel level the otarrag optstioss tor* assetsat atter lova are ehtelmed•

The Corm of thole eqvitiona is detansimiii by the Itatiaasekl seep*. theory based on Der4041 ift/S. it is SMISMOdi that the sheerved date will conform so that *ben the equation is adjusted to fit the initials final and midpoint in time for the determination of g the eieveation of sere seeps ead the initial am& final point for the detoruinatioa of As the

modal seepage eneffielsolo. Use remoialiag portion of the data also will fit the equation. In general this use food to he tn.* wadi tali sates that the wow/ use quite alosely eitesed with the fasts. The doviatiove that did eecur cm such as mould be *nested fres the unavoidable errors La the criginal data caused by the difficalty Is eliminating ocell leaks 0111 eillertaining the exact time when the eater leirel La the OW reached

the

344

or the

bask page•

gOTATION

The symbols used in the derivation of the equations fic, imputing the seepage from seems sup observations are defined *NM first used* They oft aaseaned bore for sonvenieneein Waren***

* elnatios at cater surto', in amen sup regime* tram heekt gage detaa.

s initial value of 11*

a s elevation at sere amp Marred to same 4atuaaa I.

6.300

** avulse of a 'hen H s 11400

2 elevation at eater surface in Memel referred to same datue as H

Z

e e value of Z when 0 144

$ • Elapsed time tres ebeervettee of Ile

to ta end to * initial, final and man value of to respectively. a * rikte of shop at * # Computed fres Observations of Z

and t sod aseemmat ladiNait ter period being 400mmi4mrsi• • * 0,0129, wort. area at beriacatal sestlea at small aop*

F

*

mows

mks ft. area of berismatel eseties of seepage 'up is tivere feet.

3. a depth of penetration of seepage sop WO bed of send* • voluee..time rats of seems atm* disk of soil under

seepage Ompo

Qs a emepated Vets of seepage boo iheomeisin cu. ft. per ego 04 per 24 kr*

• * a seepage seat fi dent Z f it •

•

*

Barg 'Neff talents

Is• 20303 Ail, a ooeffiaient introdused to alaplit* equatiesa. go ob 00434e K elps sysbol intiredialli so sisplity sgpstiess•

Computation of seems fres the Seepage sap date regibleo sere Weemse the, formulas are eemplisated and some of the quantities involved are quite small. For t4is reason the slide rule is mei satisfactory for the work. limmples of the ommputatiolls by the formulas end by the graphisal method are iselvded hare to Chew the prooedere amd to oompart the results'

The eite 'Obtained Ave Gas series of ebservatioos oa the Mot boa* at the Alta Gana at Mamba. Caliterais (see pages 66 to 67) us _{gives in table 2. Portia's* data derived rift the 41bearvatime.} us also included. This gat at the ties sad be* gess reatings, sibish taileates the rate of drop of the water airresta la the mil esp. is

Mesa in nose

3.

The line shoeing the Ono is lenna it the otter aorta* is _{the meal is plotted to the ism seas as the Magna. NAM}

the tie, 1011$11411% the initial and final

romitai at the

UAW ISINI1 IX

the *Sal IX 610 edastee or 40 seeoults. table 29 *al the rigs in the

eater ~flee is 0.030 toot, the vales at a ia the tersuls • Zip • at

la * _{0.0000012Si The intereeotisa at the we llas is the point}

'here the water levels is the sup sad in the semi my the ewe. In this eve* the gage height at the intereection is 0,36.2 to the lamest 04,001 foot. Kam the total tdast the dm Is the cop as observed le 1879 *wads, table 2, the gage

Implot Tits

at the aidpoint

or

latish

wet be detexeiasd Weft the temoslas ow be solved. is 0.327 foot as

sbant WU.

tinsel.*

OP SOW*

The deta required ter solving the equations sou then as follow a a .00000725 zo a 0.363 ft. s 0.360 ft. in $ 0.300 ft. * 0 1179 eau is • * ta • 940 sok Ho • 04327 ft.

r: blIt 2.

',A.),,,;;,:xva4 tlertiatmot derived vtauestr ~pm. amp

1-.1.-Imant on ;..,,st Br,wetti of 41ta Cn t DUO* GreliNrnigi*

istorjes

t

44e

Ota,vrved Culqatad CA'bvtle

• int,erv%1 Ussk ivemass **IOW per scat* Por 24 brio #s-5 6 7 0060 4,3600 *350 *3505 A4a 0402 *3)0 *120 *320 *3195 *310 .3992 -JDO 02945 • _,ze-condp 256 256 535 312 326 L0.73 348 152i 358 187/ 4447FM 400Els 092 5156F1

aka&

0,00170 .410 .0550

In this prebles, the level of the water in the 3a i$ rising and therefore upsilon (IQ

Sea _N.)

(eta) Ile • _{Ha 220}

viii haw to to used to find the elevaties ofsee* seep. lien the values illoon above are' subetituted in the aqiaotiern

• 6360) WOO)

4° Oral 2 ii4$6°°427) * S°°?34)72t0P) .360.

•300 2

(•3271

4*

0360

•

*XV

4. 2 to,3247)

.00000fl1(940)

* ams

•

.o63 x ono

Anew s has been dettentined, c eon be Obtained by substituting the Mem value in eggetioa (17)

tn IS%

lag10

1•3e1

soot Ix*

(19)

132

2

0

•

*is " (440 33414

ow new be solved fer Qs. the Seelfeele nits. anbetituting fir 10 ;PO g ed e the values previsaely determined.

(•363 .40 OW 1914(4400017725)

• •0919 0011.3 * 00(016 Os• ft• per eg• rt• per U As preivieasly stated, the derivation or the forsolas used in

eallituting the eeePh rrell the eeepeze Sup ebeervationa is tosod ark the

aseneptiso that the drop of the water surfsee in the sap fallen eez.tain toadaeots1 Uwe. This it the shooned. date at these fermata it is reemenalay *tweed the% the seloimptiosk los eorreet. The eiriataten

or

the

*33*

timewhedk gage sem *wiled is this basis is h

o • g

z • g • it le/k5

and if the theory is correct, the valves et It oomputed by this formula Should cheek the observed values of H. Hoedleeely they wee le shwa in table 2. 1* so ease is the deviation as mob as 0.001 foot,

To find the seepage rate by

the poobtaa

egothed, the some. rate of loss in sable feet per square foot pew AWk hare fer eseh interva3. is eompoted from the ebswied data. Item ialties ire given in bible 2 and are shown plotted Labore The data are plotted to the use Use , seals ea the abeam as the timemibeek gage serve. but the ordinate

Seale le *hafted

bras js

bd.* la feet to obeepage in enble feet per *pars test poor 24 beers. Stole the seepage rate &ring emth interval La the overage rate for the taterval, it is plotted at the eld pedal in time. As previously pointed out the intersoetien of the tiseoheek gap

surto with the line shoeing the change in canal lava dotormines the time and the gags height when the level in the amp in the sem as that in the esnel. The seepage from the evo aids" them semiltiome is the same as that fres the senal• It is feud yeeiling the seepage rate tree the seepage cures at the point vorties11401S4s, this isdeiSSOtieso in this ease the seepage rate is 00815 *chic toot per spore toot per 14 hours, The rate competed

by

the formai is 0.0776 oubie foot per *quer, foot par 24 hours, which in view of the small vats of seepage,

is oonsidered a satiefaetory agreement. A slow Meek 'veld probably have boon obtained if the interseetteue had ease en the serves vitae

•

.380 .370 .360 .35C Lu Lu L. — .340 ct ▪ .330 LU CD CD

•

320 .310 .300 0 200

---Water level in canal

Water level in cup

,c-Seepage rate .100 .090 cr cr .080 La .070 u) cc .050(4c. .040 .030 400 600 800 1000 1200 1400 1600 1800 2000 TIME (SECONDS)

Figaro )_{4 Chart show:1.0 mothod of dotarsiolog ssopago loss fmm}

aospage cup peraca4eter readings by Ms graphical mothmil.

the limits of the Observed date as would ncrmilto mum if the Initial level in the cup had been aboveg the eater sorties lathe essol4

Additional experiments wore oondasted with the seepage imp at Various plums in Califersie to test the effestivemees of the discice in measuring seepage. The results of these experissids, Oespated by the fornaaa se paps 25 to 29, 4111 summarised in table),

Ito series of experiments were eamdMeted at Livimotscs California on an old lateral of the Mirsed Irrigation District, which is located

in very eamdy sail elassified as Oakley and Vreeno sands, undifferentiated* In the rivet series of ebeervatIsma, the seepage sup ens installed in

the bottom of the lateral and in the seemed series items installed en the side of the lateral belie the eater's adapr• The tests Show that the seepage fres the bottom of the lateral sae vemeistently greater than that true the bask but the rates sera mush less than was sotto/pets* in vier of the moodiness of the soil. WIAM ome eueeption, the tests of ea* series gave reesoriably consistent results. The eeepege &torsi mined from the first test of the series made Lithe tett* at the lateral is definitely lower than the others* 100 reason is apparent why this should occur because the conditions remained the same as nearly es could be determined*

Ohmerestieme en seepage from the list iraneh °asal of the Alta irrigation Distrist near Dismball California, were node with the seepage cop installed in the bottom of the *anal. The bed of the soma. Ala Is about 2, feet vide, is sandy end is underlain with hardpan et a depth of 4 or 5 test. The seepage rates deierained by sUbstituting the

L0exktion.

i-,1110_1. _{mry of resaIts of seoptge cup per*n4eter 06tiervgtions}

"ASO

Comwted amipage per ev,.ft.

lAstriot Ch.:a-n11,1LItArLa _{Lettlng -,lor 201ro,}

?art X0.1 test No. _{re:LA to. 3}

Livinoston

Rai bluff

2g4l1s. c41.Ftt

:Ailrco-d, Laterel .f-.- nd au...tom ti.J.ta.i

4

4,1de _'Joje95

Alta ituA Bran=

* 4ndbroon _4.4.ea C,ottorilmoa Lateral University Lateral F%rn * * * pf ,. „may 1,,,t,z -, CArnvelky auz.ton 0.0482 0.076 Iwo 0 _J.1,36 Saal*, leen 0 _2.41 • _3.605 * .157 0.2444 0.2955 0.0714 0.116 U.U436 J.054 0.0766 4.38 5.64

•15..

the melts of the eurrent aster measurements previous4 soft eatibis eamal when it vas fogad that the looses mere se small that ther could not he detested

by ourrirat

meat pew, (see table 9). The seeond series of obmervatieas at Diambat although lisicea as tdentleal seep thieve eneept that 24 hours he* elapsed mimes the previous ebservetiona. Shamed a definitely higher rate of seepage. A 01.41air increase in the rate with time vas Obeervel in the experimemte at livimplasw

Cement meter UNI,~011.40 se a portion at the are* Lateral of the

Andersen.Cettompeed District near Red Sluff', Califersia disclosed * 110011W* rate of over 5 ambits feet per square foot per 24 hours, (see table 9). The lateral as. excavated in a gravelly lees and there mere visible indicaticms of rm*page. Observations with the ~page emp at a point in the upper end of the lateral shoved a lees of only 0401 cubic feet per square fist per 24 hours. In explanation of this extreme variability, it should be peisted out that the seepage cup immurement. were made in a *potion nbere there were no visible isii•

cations of seems. Furthermore5 pools in the main *anal lathe same gravelly lows Imre feud sibleet to prastieally no lame from m00.011,4

Several series of Observations mere as with the seepage cop on a lateral at Davis, Califormia on the University farm. This lateral*

which vas supplied by a pump, vas excavated in Telo sandy lam. The results of the first eerie* of measirements (table 3) are of the same Ardor of milidinde bet the imams* is the vats with time is evident aloe tram these observatiome4 The seepage rate iletendamili tribe seepage cop agrees messes:47 well with the direst meesurememils from

in a somewhat heavier soil olaselfted as Yale als lose. tot the

differenee In so would, however, be loOrdaMieed10! the feet that the lateral had been in ass for a araber of rum Aen the seepage amp was reset amuck levier rate of lee* vas found and skin the seepege S w seved a, seeeel time, a further decrease occurred,

The last eerie. of ObserestleassiedipIleated and in this ease the slater level in the imp vould not tan hels* the eater level in the lateral* This leads to the sonoluelms that straw tripped in the hose.

Sines the elevation of sero seep is silly oily a Shirt distal* blase that of the eater in the easelit escall amount stair is *obi* wield result in *stir* erreseeme readisigs* Aar the sees reams It sas be assumed that entrapped sir mused the apparent drop in the seams rats Shown by the second and third series it Obeervetions•

Although the results of the seepage imp aipertsants are apt eons elusive, it Is believed that this devise has merit and it sormater ears Imre esereised in gettlmg the sir out of the hose and seepage sip hews ~Us, ebservetleaft ors esesielest results lead be obtaimed. Sethi

the seepage ear with a eeeteal top mould help avoid trapping dr. Seepage rates distandamt tir swiss* Imp etwerwatlime Should be *leaked agelmet seepage avemuremeate brother mass *ere possible in order to fled eat *ether the results are easurates

%spatial Tallorbsomik sad Tit thoseisisits

The observations it some eigimeere and irrigators bee led them ti believe that the seems through the sides of a canal Is ipmerelly greeter than It is Ape* the bottom. It this is trues a seasiderehle swim is the west it liming large oanals could be achieved because it

oVis.

maid net be nesessary to lice the bottom of the semi *bleb eaprisee a large portion of the perimeter • Se feasible method of seasurtag the bulk ad bottom seepage fres a easel independently has been pereatedi bet It us thought tba t it the seepage free a series of pits end trenches in the Sues type at sell end differing only in dimensione mks meneered,

mathemati eel rela ti ons amid be developed 'etch amid mike it possible to segregate the bctton and the side seepage.

Sines the seepage near the earners of the pits and trenches would be different tram that through the sides, this effeet *as eliminated by making the pits some in plan with the sides and depth equal to the width and depth of the arreapondleg trade,* and then subtrating the pit seepage free the trade seopegea riMiqmeatity remaining amid

represent the seepage from the stism and UK= smetteeted /myth* earners* The treahes are of different lemelbsimiledilheip 1st the depths are the IWO inept in one Instance' donsequent4 for some at the trembee the bottom area as greatest and for ethers the side area was greatest.

The trenehes and pita Imo sessomed by keeping then filled with water until the seepage rate beans fairly constant. After auditions beans stabilised, same observations were made by noting the time required for a measured quantity of eater to seep out or the trench or

pit. AspreviAmairmemethendip the seepage tram via pit vas subtracted from the earespemdieg treash4 The rensinteg mem* rspresested the unit rate of mopgs lire* the sifts, times the mos of the sides, plus the it rate of seepage through the batten of the trench, times

the area of the bottom* This relation mem empeased in an equation im 16146 the sapege rates are the lebncia* Simile, independent

L

egmations were formed far the trenehes of other -widths en4 lengths. Use. there WO _{osAy teeseinnen04 the alit rate of seepage throuith}

the sides and through the butte the equations were oombined

addition to make the number of equations equal the member of adememes. One series of pits and tremolo's was exesvated in a moderetely

heavy soil on a tract of land about 4 _{silos west of El Centro, California.} This sell is classified as Holtvills silty clay loam and is underlain by a somewhat lighter tolutred soil. figure 4 Shows 4140 treadles in this tract. Another series of pits and trenches was excavated in sandy soil en a treat about 3 _{miles southwest of 111 Centro. This soil} is elassified as Weiland fine 'wady loam. The underlying material in this ease is a heavier mil. The some preseduro was followed immalcimg the observations we seems from the different soils.

The total seepege pow 24 hours was oempated for each trench and pit from the rates during the period of :be test and the seepage free sub pit was subtracted free the eorresponding trench. The remainder, whieh represented the seepage from the trench without the ends was used im the seepage cootie's. After the equettene were sombined5 the bottom end side seepage use oomputed by solving the equations. These unit ratite were multiplied by the are*s of the bot,tame and sides of the trenches esolusive of the ends. The sea of these products for each trough Should equal the observed seepage for this portion of the trench* A emmmar, of the results is given in Tittle 44

Although the Obeerved and 000uted rates are in close agreememi, La the latrine silty *ley loam the side seepage elessedi the bottom seepage, whereas in the Ueloland fine sandy lege the reverse is true.

Figure 4.- TrxIches in Holtioille ellty clay loam ne,,r El L;antro, California*

,

tabl 4, Stelrstry at ru1te of twet.c... to determine bottom and *Ade sompage hoe

trowel/as tit ;tea= lad 0-:07 *oil*.

Langth (ft.) 10 10 5

ridth (ft.) ^ V*' 1.667

0.583

Deptil of imter at.; 3.627

p.‘29

es../Msemr.

Oirinceirad tiotal

(046-80 por 24 biro 9493. 17.4 5

Choorit.d

(7311,ft,per -.,

Com?4ted Q416pas, bottom*

(tutorti rot *tat, ow 44 br.) 0,645

Oompatod seepue 444408 and bottou

(an41,0 ?tor 2.ktr,)(Inidn itistirv4ed) 3,44 3.926

Stowing siviptv, tads gaini 11..A. tad

(mutt,per 4 hr.) 3.543 Ii#213 3.$;1 0.604 1,257 5 O.W.4 3.647 .41101111111106.11 L;er, 40 W t. e7 10.97 7-1. ::471 0.47 0 -5,517 _5.1'73 546u 5.58

This difforonas may be doe to the difference in permeability of the soils sr might remit from differenees In the inderlying strata. The

material removed from the onsavatiems appeared to be quite uniform sod stioditery to ozpootatioare the bottom rat* oisoolod Ow olds rats 'IWO the homier substratum osourred4 Severer, it Should be noted that the ratio at side seepage to bottom seepage (Maimed by this method at

nogrogetins soulti be doossil

by

swift a different gembituktion of trenches aid pits in esnputing the results. This feet is probably due to difforenoso to the mit Moo at seepage free the trenehes and pits, even though

the exeavetians were imialftriel that appeared to he uniform. ter this reason the mathematisal method et segregating side end bottom seepage

was abandoned in fever of a direst method which is described as moo 39 to 45.

Awls Tram* ihopertnemte

In proporittion tor experiments at 'aerie. California, to lotsergas the diaereses between side and bottom seepage, two tretwhes wipe the lathe experimental plots on the vest side

at

the Agrioultural 0011010

dempas. The trenehes were ezeaveted along the same senterlims end the ends were separated

by

as interval at feet* leek %roma was 5 feet long* 2 feet wide and little mare than 2 feet deep. The soil in the

area is role clay loam. Figure 5 shame the relative legations or those Owlish*. and the tanks from which they were supplied with water. The tresskiss we divided intu oemphrtmente by 144AS of metal partitteme

es as to permit the measurement, separately from each other, of the seepage from the middle 2 foot of length of the bottom, the middle 2 feet of length et the sides, and the end asoticas• Figure 4 Shope the

•

•

Figaro 5.- Trenches and control apparstes for maintWitag constant eamtion of water surfacu in compartMents of trenches, Davis, California.

•

2

•

firound surfs** . SECTION A-A //A Bottom of trench Wider serfs. SECTION B-B

Note- Diaphragms extend 2 inches Into soli on sides and bottom.

Figure 6.— Plan and sections of Davis trenches snowing arrangement of compartminItsi