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है”ह”ह

IS 9447 (1980): Guidelines for assessment of seepage lossesfrom canals by analytical method [WRD 13: Canals and CrossDrainage Works]

Is:9447~1980

Indian StandardGUIDELINES FOR

ASSESSMENT OF SEEPAGE LOSSES FROMCANALS BY ANALYTICAL METHOD

Canals and Canal Linings Sectional Committee, BDC 57

Chairman RepresentingSHRI S. B. KHARE Chukha Hyde1 Project, Bhutan

MembersADDITIONAL DIRECTOR Irrigation and Research Institute, Khagaul

( Patna )ADMINISTRATOR Irrigation Department, G o v e r n m e n t o f

Maharashtra, BombaySHRI N. C. BHATNAQAR Central Ground Water Board, ChandigarhSnax CHICKARMANE Union Carbide India Ltd, Bombay

SWRI S. K. KARAMCHANDANI ( Altarnate )CHIEF ENGINEER Irrigation and Power Department, Government of

Andhra Pradesh, HyderabadDR J. PU~USHOTHAM ( Alternate )

CHIEF ENGINEER ( C ) Irrigation Works, Government of Punjab,Chandigarh

DIRECTOR CENTRAL DESIGNS ( Alternate)CHIEF ENC~NEER ( IRRIGATION ) Public Works Department, Government of Tamil

Nadu, MadrasSR DY CHIEF ENGINEER ( IRRIGATION )

( Alternate )CHIEF ENGINEER ( I R R I G A T I o N ) Public Works Department, Government of

( SOUTH) Karnataka, BangaloreCHIEFENGINEER( TUNGABHADRAPROJECT) (Altevzatc)

SHRI 0. P. DATTA Beas Designs Organization, Nangal TownshipDR R. J. GARDE Water Resources Development Training Centre,

University of Roorkee, Roorkee ( UP)DR A. S. CWAWLA (Alternate)

DIRECTOR Irrigation Department, Government of Rajasthan,laipur _

DIRECTOR ( B & CD-I ) Central Water Commission, New DelhiDEPUTY DIRECTOR ( B & CD-I )

(Alternate )DIRECTOR ( B & CD-II ) Central Water Commission, New Delhi

DEPUTY DIRECTOR ( B & CD-II j( Alternate )

( Continued on page 2 )

@ Copyright 1980

INDIAN STANDARDS INSTITUTIONThis publication is protected under the Indian Copyright Acf (XIV of 1957) andreproduction in whole or in part by any means except with written permission of thepublisher shall be deemed to be an infringement of copyright under the said Act.

IS : 9447 - 1980

( Continuedfiom page 1 )Members

SHRI K. M. MAHESHWARI

Representiq

Planning Commission, Government of India, NewDelhi

SHRI N. K. DIKSHIT ( Alternate )SHRI Y. K . MEHTA Concrete Association of India, Bombay

S HRI E. T. ANTIA (Alfernate )SHRI GAURI KANTA MISRA Irrigation Department, Government of Uttar

Pradesh, LucknowSHRI R. K. AQOARWAL ( Ahnate)

SHRI G. H. RODRICKS Fibreglass Pilkington Ltd, BombaySHRI E. SUBRAMANIAN ( Ahrnate )

SHRI P. C. SAXENA Central Water and Power Research Station, PuntSHR~ V . P. BHATT ( Alternate )

SECRETARY Central Board of Irrigation and Power, New DelhiSHRI M. K. SINCHAL Irrigation Research Institute, Roorkee

SHRI JAGDISH MOI~AN ( Alterndc)S HRI K. T. SUBUDHI Irrigation and Power Department, Government of

Orissa, BhubaneshwarSUPERINTENDINOENGINEER Irrigation and Power Department, Government of

( PROJECT & DESIGN C IRCLE ) Haryana, ChandigarhSUPERINTENDING ENGINEER (S. Y. L .

DESIGN CIRCLE ) ( Alternnfe )SHRI D. AJITHA SIMHA, Director General, IS1 ( Ex-ofjcio Member )

Director ( Civ Engg )secretary

SHRI V. KALYANASUNDARAYAssistant Director ( Civ Engg), IS1

2

IS : 9447 6 1980

Indian StandardGUIDELINES FOR

ASSESSMENT OF SEEPAGE LOSSES FROMCANALS BY ANALYTICAL METHOD

0 . F O R E W O R D

0.1 This Indian Standard was adopted by the Indian Standards Institutionon 29 February 1980, after the draft finalized by the Canals and CanalLinings Sectional Committee had been approved by the Civil EngineeringDivision Council.

0.2 Irrigation project design, operation and maintenance, and canal liningresearch and development, require accurate and economical measurement ofseepage rates. The possible benefits from canal lining are saving in water,elimination of waterlogging, and reduction in maintenance cost. Hence,correct assessment of seepage losses from unlined canals is very importantfor evaluation of benefits from lining and field observations.

0.3 The loss of water by seepage from unlined canals in India generallyvaries from 0.3 to 7.0 m3/s/106 m2 depending on the permeability of soilthrough which the canal passes, location of water table, distance of drainage,bed width, side slope and water depth inside the canal. In addition, flowvelocity, soil, water temperature, atmospheric pressure and stratification ofthe underlying soil also affect the seepage rate.

0.4 The seepage losses from unlined canals can be calculated by analyticalmethods or determined by direct measurements on the channels. Theanalytical calculations of seepage losses based on coefficient of hydraulicconductivity of soil and the boundary conditions of the flow system, are ofparticular value for the canals which are in the planning stage. The methodof direct measurement of seepage losses are applicable to the existingcanals.

0.5 Currently, accepted methods for direct measurement of seepage lossesfrom existing canals are the ponding and inflow-outflow. In addition, thereare special methods such as tracer technique, seepage meter, electrical loggingor resistivity measurement, and piezometric surveys. The ponding andinflow-outflow methods are applicable regardless of canal or soil conditions.The seepage meter cannot be used where the channel has rocky bottom orheavy weed growth. The tracer technique is best suited to canals inhomogeneous and isotropic formations.

3

IS -: 9447 - 1980

0.6 Valuable assistance has been rendered by Dr A. S. Chawla, Professor,Water Resources Development Training Centre, Roorkee, in the preparationof this standard.

0.7 In the formulation of this standard, due weightage has been given tointernational co-ordination among standards and practices prevailing indifferent countries in addition to relating it to the practices in the field inthis country. This has been met by deriving considerable assistance fromthe following publications:

GARG, SATYA P., and CHAWLA, A. S. Seepage from TrapezoidalChannels. Journal of the Hydraulics Division, AXE, Vol 96,No. HY6, Proc. Paper 7335, June 1970, pp. 1261-1282.

SHARMA, H. D. and CHAWLA, A. S. Canal Seepage with Boundary atFinite Depth. Journal of the Hydraulics Division, ASCE, Vol105, No. HY7, July 1979.

VEDERNIKOV, V. V. Seepage from Triangular and TrapezoidalChannels. Machine Zapiski, Moskovskogo Institua InzhenerovVodnogo Khozyaistva No. 2, pp. 248-288, 1936.

1. SCOPE

1.1 This standard deals with assessment of seepage losses in open channelsby analytical method.

1.2 This standard is applicable in open channels along water shed which arenot normally subject to recharge from the ground water.

2. NOTATIONS

The following symbols are used in this standard:B - width of channel bottom in z-plane ( metres )

B, = width of channeI water surface in z-plane ( metres )b = width of channel bottom in &plane ( metres)H = water depth of channel ( metres )

11 - drop between channel and drain water levels ( metres )k = coefficient of permeability ( metres/sec )L = ~drainage distance from water line of the channel ( metres )(I = volume rate of seepage per unit length of channel (cubic metres/

set/m )T = depth of pervious medium from drain bed ( metres)

XK = canal side slope angle with horizontal in z-plane ( radians )XU’ = canal side slope angle with horizontal in &plane ( radians )

4

IS :9447-1980

u, p, y = transformation parameters (dimensionless)0= Ol+i(l: ’complexvariable representing Zhukovsky’s function

d = potential function

3. ANALYTICAL METHOD

3A The -seepage 10SWS from unlined canals depend on the canaldimension, the permeability of the subsoil, distance of governing drainagesand the difference in the water levels of canal and the drainage. Initialseepage losses are high due to steep gradient, but as the subsod becomessaturated the gradients flatten and ultimately stabilize.

3.2 Analytical solutions are available for evaluating seepage losses fromcanals under steady conditions for the following cases. The solutions givenhere are for homogeneous and isotropic medium. The flow is assumed to@ laminar and hence follows Darcy’s law.

a) Canals located in medium extending up to inffnite depth withshallow water table;

b) Canals located in medium extending up to finite depth with shallowwater table; and

c) Canals located in medium extending up to infinite depth with deepwater table.

3.3 The seepage from canal, for cases indicated in.(a) and (b) above flowsto the drains -in a direction approximately transverse to the direction offlow in canals and drains. The lines of flow from canal meet the drains atvarious dopes, depending upon the cross section of the drain. The problemcan be simplified to the following two extreme conditions ( see Fig. 1 ).

3.4 Horizontal Drainage — If the drain is shallow and wide, the streamlines of seepage flow from the canal may join the bottom of the drain atvarious points along its width as shown in Fig. 1A. In this case the bed ofthe drain represents an equip otential surface.

3.5 Vertical Drainage

3.5.1 If the drain is narrow, the seepage might enter it from both sides ofthe drain as shown in Fig. lB. In this case the streamlines of seepage flowfrom canals on both flanks of drain would reach the drain in a horizontaldirection, and a vertical plane along the line of flow of the drain may beconsidered to represent an equip otential surface. Such a flow situationmay also arise when seepage occurs from a canal to a shallow water table.Far away from the canals, in the zone of uniform flow of ground water,the streamlines would be almost horizontal and the equipotential linesnearly vertical. Such an equipotential line may be considered to representa vertical drain,

.5

— —.___.._. . .. .,-.,. .-,.

.

.

.,,

.’

IS :9447-1980

AL

1A Horizontal drainage IB Vertical drainage *

FIG, 1 SEEPAGEFROMCANALSTO DRAINAGES

3.5.2 In practice the flow may not fall distinctly into either horizontal orvertical drainage but may be a combination of the two. In such cases afair idea of the flow would be obtained by a study of the two extremecases.

3.5.3 The solution of the problems is obtained by conformal mapping bytransforming the physical plane on to rectangular flow field throughintermediate fictitious planes. The derivations obtained are rather involved.However, the results are plotted in the form of curves which make it easyto obtain the seepage discharge and the phreatic surface for any canal.

4. COLLECTION OF DATA

4.1 In order to assess the seepage losses and the profile of water table oneither side of the canal, following data shoul~ be collected:

a) Bed width of canal;b) Water depth inside the canal at full supply;

c)

d)

e)f)

to

Side slope of the canal;Distance of the governing drainages on either sides of the canals;

Dry season and rainy season water level of drains on either side;Coefficient of permeability of the subsoil: The value of coefficientof permeability would be determined in field by a suitable methodsuch as pumping out test; andProfile of the subsoil to find out if any effective impermeable layerexists and its depth.

6

~lMm.w.—r——m—— “.-w- .- E ,-”-.,. —-,. . , ,, ,

——.—.. .__ —-._______ -. -.—

/.

,,, .

.’

... -.,.,

IS : 9447 - 1980

4.2 The drainages at which the above information shall be collected shalldepend upon the order of variations in its. values of above parameters.Where variation in the subsoil permeability, the drainage distance and thedifference in the water levels of the canal and drain is large, the data shouldbe collected at a spacing of 2 km. Otherwise it may be collected at every5 to 10 km spacing.

5. ESTIMATION OF SEEPAGE LOSSES AND PHREATIC SURFACE

5.1 Canals Located in Medium Extending Up to Infinite Depth, With ShallowWater Table

5.1.1 The procedure, both for horizontal and vertical drainage conditionis given below.

5.1.1.1 Horizontal drainage - Knowing the dimensions of the systemin the physical plane, the two parameters l3 and y are determined as follows:

a) The bed width B, the slope angle x u in radians, the~distance up todrainage L, the water depth inside the canal H and the differencein water levels of the canal and drainage h are recorded for thesubject case ( Fig. 2 ).

b) Figure 3A can be used to obtain values of transformation parametersof p and y. The use of figure requires the values of b/H, L/Hand CL’ where b and a’ are bed width and side slope of the channelin an intermediate plane. To start with the initial values of b anda’ may be taken as equal to p and a respectively and values ofp and y obtained from Fig. 3A. The values of b/H and L/Hare represented along ordinate and abcissa of the graph respecti-vely, for values of a’ equal to 0.15, 0.25 and 0.35. The scalescorresponding to the value of 0~’ are used for determining the valuesof p and y.

c) Figure 4 presents graphically the relationship between a and a’ andFig. 5 presents the relationship between B and b. With-the knownvalues of h/H, u, $ and y, the values of a’ and b/H are obtainedfrom Fig. 4 and 5 respectively.

d) With these values of b/H and a’, better approximation to p and yare determined from Fig. 3A and the process is repeated untildifference/variation in the values of p and y from one trial toanother is negligible. This condition is normally achieved withinthree trials.

Seepage discharge : Knowing p and y, the seepage discharge per unitlength of channel 4 in terms of kh is obtained from Fig. 6.

Phreatic surface : Figures 3A and 7 can be used parametrically toobtain x an-d y coordinates of the phreatic surface, For an assumed value

7

IS : 9447 - 1980

of variable t between zero and y, a ratio t/y is determined. With this valueof t/y and known value of e/y the value of y/h is obtained from Fig. 7. Forthe same value of t and the known value of 13, the value of x/H can beobtained from Fig. 3A by replacing L by X and y by t in that figure.

5.1.1.2 Vertical drainage - The procedure with vertical drainage issimilar. The difference is that Fig. 3B is used instead of Fig. 3A for deter-mining p and-y, and x/h.

The seepage discharge and phreatic surface profile are determinedseparately for either side of the canal. The total seepage is obtained byadding the seepage discharge estimated for either aide.

1=--X

h

2A Horizontal drainage

t= x

h

_-l-L--m

tY E

28 Vertical drainage

F I G. 2 PHYSICAL PL A N E

8

l/H IN T H O U S A N D S _

3A Values of p and y horizontal drainage

FIG. 3 VALUES OF p AND y DkAINAGEs- Con&

w

‘“\\\

\I \

I \ T

b n b

0861

- LP

P6 :

SI

IS : 9447 - 198cD

0.15 2

0.20

1

0.30 '8----_ tr

L8 0400.50 u"

0

0.60

O?O

-1

0.80

FIG. 4 RELATION B ETWEEN a AND (x'

E-3 : 9447 - 1980

8

(B-bl/H

6 2

0B

F I G. 5 RELATIONSVIP BETWEEN B AND b

lo-' 10-4 10-j

P/-fF I G. 6 SEEPAGE D ISCHARGE qlkh

12

13~. 7 ORDINATES OF FREE SURFACE

5.2 Canals Located in Medium Extending Up to Finite Depth with ShallflowWater Table - Of the various methods in vogue, closed form method isgenerally adopted which is given below.

52.1 The procedure for determining the seepage discharge for thecanal both for horizontal and vertical drainage conditions ( Fig. 8 ) is givenbelow.

5.2.2 Seepage Discharge - Knowing the dimensions of the system inthe physical plane, the two parameters IS and p are determined from Fig. 9and 10 for horizontal and vertical drainage conditions respectively. Fig. 11and 12 are used for determining non-dimensional seepage discharge qlkh forhorizontal and vertical drainage conditions respectively.

5.2.3 Phreatic Swface .--- Figures 13 and 14 can be used parametri-cally to obtain x and y coordinates of the phreatic surface. For the knownvalues of Q and CS/@ the coordinates of phreatic surface can be obtainedfrom these figures. The phreatic surface have been plotted for o=lO-“,IC-10, 10-20, IO-30 and CS/@ ranging-between 1O-2 and 102.

13

IS : 9447 - 1980

I M P E R M E A B L E L A Y E R

8A Horizontal drainage

L IMPERMEABLfL A Y E R

88 Vertical drainage

F I G. 8 PHYSICAL PLANES OF DRAINAGES

5.3 Canals Located in Medium Extending Up to Infinite Depth with DeepWater Table - The solution for this boundary condition was obtained byVedernikov with the help of conformal mapping. The seepage discharge,q per unit length of channel is given by:

q”1C[B+(A+2m)H]

=k(B,$-‘4H)

where B = Bed width of channel ; B, = Surface width of channel; H =water depthinside channel; and A is function of geometry of canal,. Thevalue of A is obtained from Fig. 15 for the known values of B/H or B,/Hand m, where m = cot rt cc and x 01 = side slope angle.

14

10

10

10

1.010:

5 lo2

::,”ij 10

lo3

lo2

10

1.0

VALUE OF ,

t.UE O F

I/I

I

I

6

V A L U E OF L/h

FIG. 9 R ELATION B ETWEEN L/h, T/h, G AND p( HORIZONTAL DRAINAGE )

15

IS : 9447 - 1980

// i / I

I I ,

1 102 103 104 105

- 1

I

_---~I. ..-0~001

_--

--~

-.. odm..’

--~--7

0B-4

10

VALUE OF L/h

l71~. 10 RELATION B ETWEEN L/h, T/h, (r AND f3( V ERTICAL D RAINAGE )

IS : 9447 - 1980

FIG.V A L U E O F L / h

11 SEEPAGE DISCHARGE ( HORIZONTAL DRAINAGE )17

IS : 9441- 198014

n

WITHOUT CLAY

WIT

2 IIO5

VALUE OF t/h

3UT CLAY

-.-WITHOUT CLAY

LAYER7

IO4 105

F I G. 12 SEEPAGE D ISCHARGE ( VERTICAL D RAINAGE )

18

IS : 9447 * 1980

VALUE OF x/L

FIG. 13 COORDINATES OF PHREATIC SURFACE

( HORIZONTAL DRAINAGE )

19

IS : 9447 - 1980

1 -30d) 6=10

0 0.2 aI.4 0.6 O-6 14,O O-2 04 O-6 O-0 1.0

VALUE OF x /L

F I G. 14 COORDINATES OF PHREATIC SURFACE

( VERTICAL DRAINAGE )

20

IS : 9447 - 1980

4.4

4.0

3b6

A 3.2

2*0

2.4

2-o

la60 5 10 15 20

61"

FIG. 15 VALUE OF A

6. LIMITATIONS

6.1 The drainage conditions on either side of the canal are assumed to besymmetrical and in practice may be different. The seepage losses andphreatic surface for both the sides are determined separately assuming thatthe dividing line is vertical through the centre of the canal.

7. EXAMPLE

7.1 A worked out example for cases given in 3.2(a), 3.2(b) and 3.2(c) isgiven in Appendix A.

A P P E N D I X A

( Clause 7.1 )

A WORRED OUT EXAMPLE FOR CASES GIVEN IN 3.2(a),3.2(b) and 3.2(c)

Following are the physical dimensions of a canal for which seepagedischarge and free surface on either side are to be determined ( Fig. 16 ):

a) Bed width B = 68.8 mb) Water depth H = 3.44 mc) Side slop angle 0.147 77 x

21

IS : 9447 - 1980

Right side of channela) Drainage distanceb) Difference in channel and drainage

water level

L-53QOmlz = 725 m

Left side of channela) Drainage distanceb) Difference in channel and drainage

water level

L = 10 600 mh= 8*4m

L E F TFSL OF CANAL

RIGHT

#w WLa:cwz go- SURFACE

I t*oL 10I I I L I

8 6 4 2 Q 2 L

D I S T A N C E I N k m

FIG. 16 CROSS SECTION SHOWING PHREATIC SURFACE

For the case corresponding to 3.2 (a) the seepage losses are workedout as follows:

Horizontal Drainage: For values of CL, B/H, L/H equal to 0.147 77,20.0 and 1 540 respectively for the right-hand side, Fig. 3A, 4 and 5yield the values of p = 3.5 and y = 5.0 x 10.4. For these values ofp and y, the non-dimensional seepage loss q/kh is obtained fromFig. 6 as 0.52. Similarly the values of p and y for the left-hand sideare obtained as 3.7 and 2.3 x 10” respectively. The value of non-dimensional seepage discharge q/kh from Fig. 6 is obtained as 0.47.Taking an average value of coefficient of permeability equal to 2.5 x lo5m/s, the seepage losses work out equal to 0,094 ms/sec/km and0.099 ma/s/km considering the right and left sides boundary conditionrespectively. The average value of seepage losses works out as0.096 5 ma/s/km.

22

IS : 9447 - 1980

Vertical Drainage: For values of a, B/H, L/H equal to 0,147 77, 20.0and 1540 respectively for the right-hand side, Fig. 3B, 4 and 5 yield thevalues of @ = 3.5 and y 5= 2 x 1Q4. For these values of p and y, the non-dimensional seepage loss q/kh is obtained from Fig. 6 as 0.55. Similarlythe values of fi and y for the left-hand side are obtained as 0.48. Foraverage value of coefficient of permeability equal to 215 x 10-s m/s, theseepage losses work out equal to 0.099 ma/s/km and O*lOO ma/s/kmrespectively considering right and left sides boundary conditions respectively.The average value of seepage losses work out as 0.100 ms/s/km.

For the case corresponding to 3.2(b) when the canal isassumed to belocated in medium underlain by animpervious layer at a depth of 100 m,the non-dimensional seepage discharge q/kh as obtained from Fig. 11 is0.055 and 0.019 0 respectively for the right and left sides respectively forhorizontal drainage. Similarly the non-dimensional seepage discharges,q/kh for vertical drainage case from Fig. 12 is 0.06 and 0.02 respectively.The average seepage discharge works out as 0*0071 ma/s/km and 0.007 5 m3/s/km for the horizontal and vertical drainage conditions respectively. It isseen ~that these values are less than those obtained with infinite depth ofpermeable stratum.

For the case corresponding to 3.2(c) when canal is underlainby deep water table the seepage losses work out 2.37 ms/s/km which arevery large in comparison to values obtained for the conditions corres-ponding to 3.2(a) and 3.2(b).

23

I N D I A N S T A N D A ’ R D S

ON

CANAL AND CANAL LININGS

IS :

4839 (apart II )-1979 Code of practice for maintenance of canals: Part II Lined canals (Jirstrevision )

4839 ( Part III )-1979 Code ofpractice for maintenance ofcanals : Part III Canal structures,drains, outlets, jungle clearance, plantation and regulation (Jirst revision )

4969-1968

5256-19695331-19695690-19695968-19686004-1971

Method of test for determiningfl exural strength of precast cement concrete slabsfor canal liningCode of practice for sealing joints in concrete lining on canalsGuide for selection of type of lining for canalsGuide for laying combination lining for existing unlined canalsGuide for planning and layout of canal system for irrigationCriteria for hydraulic design of sediment ejector for irrigation and powerchannels

6522-19726936-19737112-19737113-19737114-19737495-1974

7871-1975

7873-19757880-1975

Criteria for design of silt vanes for sediment control in offtaking canalsCriteria for location, selection and hydraulic design of canal escapesCriteria for design of cross section for unlined canals in alluvial soilCode of practice for soil-cement lining for canalsCriteria for hydraulic design of cross regulators for canalsCriteria for hydraulic design of silt selective head regulator for sediment controlin offtaking canalsCriteria for hydraulic design of groyne walls ( curved wing ) for sediment dis-tribution at offtake points in a canalCode of practice for line concrete lining for canalsCriteria for hydraulic design of skimming platform for sediment control inofftaking canal

7986-1976 Code of practice for canal outlets8835-1978 Guidelines for planning and design of surface drains9097-1979 Guide for laying lining of canals with hot bitumen or bituminous felts

3860-1966 Precast cement concrete slabs for canal linings3872-1966 Code of practice for lining of canals with burnt clay tiles3873-1978 Code of practice for laying in-situ cement concrete lining on canals (Jirst

revision )4515-1967 Code of practice for boulder linings for canals4558A968 Code of practice for under-drainage of lined canals4701-1968 Code of practice for earthwork on canals4745-1968 Code of practice for design of cross section of lined canals4839 ( Part I )-1979 Code of practice for maintenance of canals : Part I Unlined canals

(&St revision )