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Hydraulics Prof. B.S. Thandaveswara
22.1 Lining the Canals
It is always assumed that seepage losses would be reduced from the theoretical
calculations as between 3.7-1.8 cumec per million square metres (cumec/Mm2) for an
unlined canal in the sandy or clayey loams to 0.6 cumec/Mm2 for a lined canal. In 1988
a field study of the performance of lined distributaries were losing 3.5 cumec/Mm2 and
watecourses were losing 3.7 cumec / Mm2.
Why is there such a gap between assumptions at the feasibility stage and what
happens in practice?
Old earthen irrigation channels in permeable soils can lose a lot of water through
seepage. Large losses through the bed and sides of canal lead to low conveyance
efficiency; that is, (the ratio of water reaching farm turnouts to that released at the
source of supply from a river or reservoir). Earthen canals also get clogged up with
weeds which reduce the water-carrying capacity.
These two factors combine to disadvantage of the tail end farmers. Therefore Unlined
canals are inefficient, inadequate from the point of view of equitable performance.
In Punjab, the expected saving by brick lining is of the order of 20% . The brick linings
have 25 years of life.
Total losses from unlined watercourses are known to be more than those from the main
system, but they dont get the same attention during a lining programme. Lining
programmes are divided into main system lining and watercourse lining. The main
system canals (main, distributaries, and minors) are large channels supplying several
watercourses.
A typical value for the seepage rate in an unlined channel in clayey loam is 1.8 m3/s per
M m2 and through a rendered brick line water course or canal reduces to 0.1 m3/s per M
m2. However, if the impervious canal lining has few crack what would happen? The
experiments indicate it as good as that of the original unlined case when the ground
water level is high.
Inspite of the above observation, lining can significantly reduce conveyance losses.
Lined channels have a smaller surface area for a given discharge than unlined
Indian Institute of Technology Madras
Hydraulics Prof. B.S. Thandaveswara
channels. Typically a lined channel will have 40% of the unlined surface area for a given
discharge. Therefore even at the same loss rate per unit area there will be a saving in
water. When estimating the reduction in losses from a lining programme, this should be
based on the combination of a reduced cross-section and a reduced seepage rate per
unit area.
In the Indian Punjab, measurements on lined distributaries and watercourses between
four months and seven years old showed that seepage rates from the distributaries
rapidly became comparable to seepage rates from unlined canals, whilst seepage rates
from watercourses were highly variable.
Lining of the distributary canal seemed to have had a beneficial effect on the equity of
supply between watercourses. However, the effects of lining watercourses is still to be
established.
A sample of 15 out of 130 watercourses were tested on the 30,000 ha Mudki subsystem
of the Sirhind Feeder in Ferozpur district using ponding tests and inflow-outflow
methods. The mean and variability of seepage losses increased dramatically for lining
more than four years old. Some lining older than four years performed as well as new
linings, with losses as low as 0.4 m3/s per Mm2 but others has losses of up to 11.5 m3/s
per Mm2. Overall conveyance losses were significantly greater than seepage losses
alone.
The variability of conveyance losses was observed to be related to the condition of the
channels. Losses from raised watercourses with cracked or broken linings appeared as
surface leakage causing waterlogging of adjacent fields and localised crop damage.
This was due to poor quality control during construction, particularly earth compaction
behind sidewalls, and a lack of subsequent maintenance.
The design life of concrete and brick lined channels is generally assumed to be 25-50
years. Major repairs of lined channels are sometimes required within a few years of
construction. At the Kraseio Scheme in Thailand, completed in 1981, long lengths of the
concrete lined main canals have needed to be replaced each year.
In one 26-year lining test, a complete repair of the drained test channel was required
every 22 months.
Indian Institute of Technology Madras
Hydraulics Prof. B.S. Thandaveswara
There is no watertight case for or against lining.
If lining goes ahead, a high standard of construction is essential, especially of water
courses which must withstand a great deal of wear and tear. Without adequate
supervision, poor construction of channels will lead to reduce life and higher
maintenance costs.
Earthen watercourse in the Bikaner area of Rajasthan discharge an average 28.3 l/s,
but begin to seep and leak badly after little more than a year. These cracks and the slow
movement of shallow water favours developement of thick aquatic weeds, which
encourages the drying and the cracking process, and strcuturally weaken the banks.
This obviously adds significantly to the cost of maintenance.
The cracks opened in dry periods do not close fully when saturated by water flows, and
losses can be up to 25% of the water diverted into the system.
The cycle of swelling, heaving, shrinkage and settlement leads to progressive bank
deterioration. Shear strength of clays depends on cohesion between particles. In a
newly-formed compacted clay masses the interparticle cohesion is high. On first drying,
the cracks appear and close up again on wetting, but do not regain their original
interparticle cohesion. This means a reduction in shear strength after a few drying and
wetting cycles.
The reinforced concrete lining would reduce the seepage loss drastically and has lower
operation and maintenance costs.
Reference
World Water, April 1989, pp 16, 19, 21.
Appendix (i)
Table - 1 Salient Aspects of Seepage through Lined Canals [7]:
Sl.No State Adopted practice
1 U.P. Ql = 1 / 200 ( B + D )
2/ 3
Practice
Ql = Seepage losses in cumecs/km length B and D are bed
width and depth.
2 Punjab & Kl = 1.9Q1 / 6
Haryana
K l = Seepage loss in cumecs / 106 sq.mof wetted area.
Q = Main discharge in the canal.
Indian Institute of Technology Madras
Hydraulics Prof. B.S. Thandaveswara
Bhakra Lined canal Kl = 1.25Q 0.056 (F.P.S)
3
Nangal Unlined canal ql = 0.00928Q 0.5265 (M.K.S)
4 Andhra lined canal: Ql = 0.60 cumecs / 106 m 2 of wetted surface
Pradesh
Unlined canal: Ql = 1.85 to 2.40 cumecs / 106 m 2 of wetted
surface and 20% extra for distributory system.
5 CBIP Main canal - 7% of head discharge
Distributory and minors - 8% of head discharge
Water surface - 20% of head discharge
Table-2 Salient Aspects of Seepage through Lined Canals (After Yu. M. Kosichenko [8]):
Type of lining and
Sl.
character of Permeability Kl m/s seepage loss Q m3/sec/m2
No.
disturbance
I Concrete-film lining
i. Smooth 0.705 * 10-9 / 0.141 * 10-7 0.334 * 10-4 / 0.685 * 10-5
ii. Crack with rough
0.652 * 10-9 / 0.136 * 10-7 0.318 * 10-6 / 0.665 * 10-5
walls
iii. Silted cracks 0.137 * 10-9 / 0.156 * 10-7 0.318 * 10-8 / 0.76 * 10-7
iv. Without cracks 0.590 * 10-11 / 0.114 * 10-9 0.228 * 10-8 / 0.556 * 10-7
II Concrete lining
i. Smooth 0.225 * 10-8 / 0.331 * 10-6 1.243 * 10-6 / 1.516 * 10-4
ii. Crack with rough
0.867 * 10-9 / 0.202 * 10-6 0.423 * 10-6 / 0.982 * 10-4
walls
iii. Silted cracks 0.706 * 10-10 / 0.752 * 10-10 0.344 * 10-7 / 0.367 * 10-7
iv. Without cracks 0.694 * 10-10 0.388 * 10-7
III Soil film lining
i. Protective layer of
0.981 * 10-9 / 0.189 * 10-7 0.564 * 10-7 / 1.087 * 10-6
local soils
ii. Protective layer
0.221 * 10-11 / 0.425 * 10-10 0.127 * 10-9 / 0.245 * 10-8
of compacted clay
IV Soil Membrane 1 * 10-8 0.575 * 10-6
V Unlined channel - 0.295 * 10-3
Plastics as a lining material
Introduction
Water suitable for human consumption, livestock and irrigation is limited in many parts
of the world. Since precipitation is the only source of all fresh water and since it varies
from place to place, from year to year and from season to season, water must be
collected, stored and transported, if it is to be available when and where it is required.
The loss of irrigation water in a canal system occurs during its conveyance through
canal, sub-canal, distributary, minor, water course and finally during application in the
Indian Institute of Technology Madras
Hydraulics Prof. B.S. Thandaveswara
field. In a study made by the Central Water and Power Commission (1967), the losses
during the various phases of water conveyance was found to be as shown in Table
Water use efficiency in percentage
System Number of Water Field Total Net
Characteristics Canals Distributaries courses Losses Loss Utilization
Entire system
15 7 22 27 71 29
unlined.
Only Canal
4 7 25 30 66 34
lined.
Canal and
Distributary 4 2 26 32 64 32
lined.
Whole system
4 2 6 42 54 46
lined.
It may be observed that, in a completely unlined canal irrigation system the loss of
irrigation water is as much as 71%. This loss is attributed to both evaporation and
seepage losses; evaporation losses are a function of temperature, humidity and wind
velocity. It is not practicable to prevent evaporation loss (in some reservoirs this loss
has been prevented by floating a thin PE film on the water surface) in running water.
However, seepage losses could be effectively minimised by the use of an impervious
medium between the porous soil and the water flowing in the system.
Conventional materials like clay, tiles, cement-concrete, have been used for prevention
of seepage losses. Most of the conventional methods are either too expensive or not
very effective.
Table 2 shows the state wise break-up of irrigation resources and the length of major
irrigation canals operating in each state.
Irrigation and Power Research Institute at Amristar has particularly conducted intensive
research in this field and a suitable lining technique has been evolved for existing
earthen canals and channels.
This technique is known as "Combination Lining" and in this, a low cost Polyethylene
film is laid at the bed of the canal or distributary whereas the sides are lined with pre
cast brick-tile blocks. This method can be conveniently adopted for lining distributaries
during short closures. This technique has many advantages over the other methods of
lining such as laying new lined parallel channels which involve construction of new
Indian Institute of Technology Madras
Hydraulics Prof. B.S. Thandaveswara
bridges, regulators, falls and outlets. Moreover, in case of combination lining, the
existing section, regime and stability of the channel are not changed. Irrigation supplies
are also not interrupted as lining is done during short closures.
Table 2 Statewise distribution of Irrigation area under major irrigation canals.
Name of Average Net Percentage of net area irrigated in Length
State/ Unionrainfall irrigated 1970-71 by various sources of major
Territory in cm area canals
'000 in km
hectares Canals Tanks Wells Others
1970-71
Andhra 900 3313 48 34 15 3 1,242.8
Assam 240 572 63 - - 37 137.2
Meghalaya 241 37 - - - 100 -
Nagaland 193 12 - - - 100 -
Manipur 193 65 - - - 100 -
Sikkim 355 NA NA NA NA NA NA
Tripura 193 22 - - - 100 NA
Bihar 132 2160 38 8 25 29 906.2
Gujarat 81 1209 17 2 80 1 2,437.2
Haryana 76 1532 62 - 38 - 1,098.3
H.P. 184 91 - - 1 99 -
J&K 102 279 98 - - 2 32.0
Karnataka 104 1137 37 32 23 8 2,924.6
Kerala 267 431 49 17 1 33 491.9
M. P. 123 1480 48 9 38 5 238.4
Maharashtra 106 1427 22 16 57 5 2,546.1
Orissa 153 1149 23 51 4 22 613.7
Punjab 64 2888 45 - 55 - 501.2
Rajasthan 46 2132 35 13 51 1 869.4
Tamil Nadu 97 2592 34 35 30 1 561.4
U. P. 117 7190 48 34 15 3 1,683.5
W. B. 174 1489 65 20 1 14 1,666.0
All India 161 31207 40 14 38 8 17,949.9
NA- Not Available (a) Includes Harayana. (b) Included in Punjab. * Source : Irrigation
Commission (1972).
Nearly 30 to 80 percent cost saving could be achieved by using combination type of
lining as compared to double tile lining. The behaviour of this lining laid in different
channels in Punjab has been studied and it has been found that this low cost lining is
durable, efficient and quite suitable for lining the existing distributaries.
Gujarat State Irrigation Department is also using Combination Lining. To render the
canals seepage proof, a 400 gauge (100 microns) thick black LDPE film is used to line
Indian Institute of Technology Madras
Hydraulics Prof. B.S. Thandaveswara
the bed of the canal which is then covered with single layer brick masonry. For further
reduction of cost, soil cover varying from 60 cm to 90 cm could be tried.
A similar trial was also carried out in Azamgarh District of Uttar Pradesh by the UP State
Irrigation Department. In this trial, 600 gauge (150 microns) PE film was used in the
canal bed overlaid with 45 cm soil cover.
The advantages of Polyethylene (PE) film lining are:
(a) Cost factor is very much in favor of PE lining in comparison with conventional lining
methods.
(b) The PE film lining has the advantage of being a superior moisture barrier than any
other construction material including cement-concrete, tiles, tar-felt, etc. Irrigation and
Power Research Institute (IPRI), at Amristar and Central Building Research Institute at
Roorkee have conducted extensive trials on this type of lining. Permeability tests on this
type of lining. Permeability tests by IPRI showed that a 400 gauge PE film subjected to
a hydraulic head of 3.65 meter has stayed water tight for about 15 years.
(c) Another advantage of this type of lining is the speed with which it can be laid at site.
By using this type of lining, the total time involved in lining work can be substantially
reduced, thus facilitating wider coverage during short closure of canals.
The Anand Irrigation Division, Gujarat, have found that with double tile lining, the work
progress is around 30 m of canal length a day (15 m canal width) whereas for the
combination type of lining using PE film with a cover of single tile masonry, the progress
is as much as 90 m. This could be still further increased by using LDPE film lining with
60 cm to 90 cm soil cover.
Distributaries:
A Canal Irrigation system comprises of a network of Canals, Sub-Canals, Distributaries,
Minors, with water courses forming the last link. In Government Canals, the jurisdiction
of the Irrigation Department is generally up to the minors. The water courses fall under
the jurisdiction of the individual cultivators.
Indian Institute of Technology Madras
Hydraulics Prof. B.S. Thandaveswara
Use of Plastics for Lining of Canals
Introduction
Canal lining with LDPE film was undertaken in the country in 1959, as a measure to
reduce seepage losses. Punjab and Gujarat States were first to use this type of lining
during 1959 to 1962 followed by other states subsequently.
The Low Density Polyethylene (LDPE), Polyvinyl Chloride (PVC), High Molecular High
Density Polyethylene (HDPE), Linear Low Density Polyethylene etc., are the plastics
used for canal lining. In India, mostly LDPE film has been used for canal lining.
The characteristics of the plastic film are:
Light in weight, impermeable to liquids and gases, chemically inert, flexibility, resistance
to microbiological attacks, ease of transportation and installation etc.
Black LDPE film lining over laid with soil cover or protective hard cover had been widely
used during the last three decades. IPCL's Petro-Chemical Industry in Maharashtra, will
be able to provide the adequate supply of this plastic film for lining of canals.
The LDPE films presently available are too smooth and glossy to hold mortar below
blocks, tile or brick lining indicating the necessity of developing rough or serrated films.
The purpose of the canal lining which helps in reduction in seepage to save water for
additional irrigation, and to increase the velocity for reduction in canal sectional area
due to smooth lined surface. Lining with bricks tiles etc., is fraught with the problem of
seepage through the joints, cracks etc. This naturally leads us to the use of
impermeable plastic film to use as a cut-off. The LDPE film is used with soil cover/ C.C.
Cover/ P.C.C. Cover. C.C. in-situ is less costly and suitable for bed but not for sides.
P.C.C. ensures quality control in case of canal lining on large scale. It is costly but
suitable for both bed and sides. In using P.C.C. pointing needs special attention. LDPE
film is susceptible for puncturing by uneven soil surface, impact of feet, weed growth
etc. A layer of sand would help as a leveling course. Sand with a little silt content or
sand wetted would stand well on slopes. If the surface of the film is rough, it would keep
the mortar in position. The hard cover over the film is meant to be the load over the film
to keep it in position and also to be smooth surface for better flow conditions.
Indian Institute of Technology Madras
Hydraulics Prof. B.S. Thandaveswara
Vandalism with regard to LDPE film is due to lack of awareness of the farmers as to the
value of water. Burrowing by rodents is a menace. The easy and practicable solution is
a sand layer. A burrow does not stand in sand, and the hole gets closed.
Lined canal costs 20 - 25% more relative to cost of unlined canal. If LDPE film is used,
the cost of lining would be 25 - 30% (an increase of 5% due to film cost). This additional
cost due to canal lining using LDPE film is rather a wise investment as the benefits of
water saved, additional irrigation and food production, and reduced canal section would
more than offset that additional cost.
Therefore canal lining is obligatory and the use of LDPE film is bound to spread once its
efficacy commensurate with economy is realized.
Films of different thickness varying from 100 to 250 micron are used in bed or on sides.
Cement concrete cover over LDPE has been used on canals as steep as 1.3:1 on Ravi
Canal (J&K), and 1:1 on Malaprabha canal.
Indian Institute of Technology Madras
Hydraulics Prof. B.S. Thandaveswara
F.S 1 1
1 1
LDPE Film
Free board
LDPE Film
Single tile lining
in Cement Mortar
LDPE Film
LDPE Film
Lining of Canal with LDPE film
Reference
"Proceeding of the workshop on Use of Plastics for Lining of Canals", Central Board of
Irrigation and Power, New Delhi, Vadodara, 7-8, May 1987
Venkatasubramanian K.N, Kamal Nanavaty, Prasanta Misra - Role of plastics in water
management published by Indian Petro chemicals Corporation Limited, Government of
India undertaking, august 1968.
Indian Institute of Technology Madras
Hydraulics Prof. B.S. Thandaveswara
Table 3 - Performance of different Canal Linings
The details regarding the design, specifications and performance of various types of
linings as provided in the case of the following projects.
S.No. Canal Type of lining
1 Nangal Hydel Channel (Punjab) Concrete and Tile Lining.
Sundernagar Hydel Channel, Beas Project
2 Cement Concrete.
(Punjab)
Concrete, Brick and
3 Yamuna Power Channel (U.P)
Concrete Tile.
4 Gandak Canal (U.P) Brick Tile Lining.
5 Lower Ganga Canal-Link Canal (U.P) Sandwiched Brick Lining.
Cement Concrete Tile
6 Kosi Feeder Channel (U.P)
Lining.
Tiles Lining with plasting,
7 Rajasthan Feeder Channel (Rajasthan) Single tile lining in bed and
double tile lining in the side.
Banaskantha Left Bank Main Canal of
8 Cement Concrete Lining.
Dantiwada Project (Gujarat)
Banaskantha Left Bank Main Canal of
9 Brick Lining.
Dantiwada Project (Gujarat)
Sandwiched Brick Tile
10 Mahi Right Bank Canal (Gujarat)
Lining.
11 Shetrunji Canal Project (Gujarat) Masonry Lining.
12 Shetrunji Canal Project (Gujarat) Lime Concrete Lining.
13 Karad Project Canal (Gujarat) Precast Blocks.
Cement Concrete and
14 Tungabhadra Project (A.P)
Rubble Masonry.
15 Krishanarajasagar Canal (Karnataka) Cement Concrete Lining.
Krishnarajasagar, Right Bank Low Level Canal
16 Soil Cement Lining.
(Karnataka)
Krishnarajasagar Right Bank Low Level Canal Lime Surkhi Concrete
17
(Karnataka) Lining.
In situ Cement Concrete
18 Manniaru Canal (Tamil Nadu)
Lining.
Cement Concrete and
19 Pattanamkal Main Canal ( Tamil Nadu)
Metal.
Cement Concrete and
20 Rethapuram Channel (Tamil Nadu)
Metal.
Random Rubble Masonry
Left Bank Main Canal, Pamba Irrigation Project
21 and Cement Concrete
(Kerala)
Lining.
Precast Cement Concrete
22 Left Bank Canal, Kuttiady Irrigation (Kerala)
Slabs.
Right Bank Main Canal, Peechi Irrigation Rubble Masonry in Cement
23
Scheme (kerala) Mortar.
24 Left Bank Canal (Kerala) Precast Slabs and Blocks.
25 Kuthanur Branch (Kerala) Bitumen and Cement.
Indian Institute of Technology Madras
Hydraulics Prof. B.S. Thandaveswara
KERS, Krishnarajasagar had tried HMHDPE film (Tuflene) covered with 1:4:8 or 1:5: 10
Cement Concrete in a length of 140 m on 38.4 km distributory of Visveswaraya Canal
and reported about 90% reduction in seepage losses when compared with unlined
reaches. Likewise Fibre glass Reinforced Plastic Tissue Asphaltic Canal Liner had been
experimented.
Backing Material for Swelling Soil
I.I.T, Bombay after conducting field studies with various types of backing materials in
swelling soil (especially black cotton soil) area in Karnataka has suggested that a 1 m
thick cohesive non-swelling (CNS) layer covered with P.C.C. slabs would suffice the
need for lining in swelling soil. The minimum specification suggested for backing
material is
Gravel - Less than 10 percent,
Sand - 30 - 40 percent
Silt - 45 - 50 percent
Clay - 20 - 25 percent
Compaction - 96 percent of standard proctor density, in layers not exceeding 20
cm.
Moisture content - OMC ± 1.5 percent.
Shear Parameters - 0.2 kg/cm2 25° to 0.5 kg/cm2 for 2 to 15°
KERS, Krishnarajasagar had conducted experiments with different lining materials, viz.,
(1) Size stone pitching over 22.5 thick layer of murrum backing, (2) Rough stone
pitching over 15 cm thick layer of murrum backing, and (3) 15 cm, 22.5 cm and 30 cm
murrum lining without any protective cover for small channels only.
The size stone pitching and rough stone pitching have functioned well and have
recommended size stone pitching for small channels in view of lower rugosity coefficient
and lesser maintenance cost though it is slightly costlier initially.
Indian Institute of Technology Madras
Hydraulics Prof. B.S. Thandaveswara
PCC lining with
1 m thick CNS layer
drainage arrangement
IP 2.43
3.04
3.04
3.04
2.74 3.04
1.82 1
15 cm thick
CNS layer 2.74 FSD
1
2 __
2
Typical section in deep cutting of Malaprabha Right Bank Canal kilometer number 35.354
2.103 m
PCC lining
FB 3.04
3.04
3.65
3.04
2.74
15 cm thick
CNS layer 2.74 Full Supply Depth
1 m thick CNS layer
Typical section in cutting at MRBC kilometer number 35.354 (a) Canal section in cutting
(a) Canal section in cutting
PCC slab lining 2:1
1 m thick CNS
FSD 2.74 IP 2.43
Black Cotton soil
SR 4.26
30 cm thick CNS
2 m and below Rock toe
1m
B
__ + 2y L
30 cm thick sand blanket
30 cm thick CNS 2
2.74
Bed filling 2 m and below
PCC slab lining 2:1
SR 4.26 1 m thick CNS 2.43 Black Cotton soil
30 cm thick CNS
60 cm thick CNS
2.74 FSD
2.74 Rock toe
below 2 m bed filling 2 m and above
1m
B
__ + 2y L
30 cm thick sand blanket 2
60 cm thick CNS
Bed filling 2 m and below
(b) Canal section in embankment
Construction of Malaprabha Right bank Canal in expansive soil area using Cohesive
Non-swelling Soil (CNS) layer of 1 m thickness as suggested by IIT-Bombay
Indian Institute of Technology Madras
Hydraulics Prof. B.S. Thandaveswara
Geo synthetic Reinforced Canal Lining
Currently, in India the lining systems adopted generally consist of three components.
The top is usually a lining cover of either concrete slabs or brick tiles. Sometimes
flagstone or soil as cover has also been used, depending on suitability. Below the cover
a LDPE lining is provided underlain by a graded sand filter normally placed to account
for planned drainage. Film of 175 micron thickness has been used in the bed lining of
Indira Gandhi Main Canal in Rajasthan. The thickness of the LDPE film depends on
whether it is the primary water barrier constituent of the lining (in that case the thickness
varies from 150-250 micron) and the rigid cover is provided to protect it against damage
and heaving. The rigid cover may also be provided as the main lining and the film is
provided as a secondary back up specification (generally 100 micron film is provided for
this purpose). Figure shows typical details of LDPE lined canal system used in India.
A
B
C
D
E
Details of Sandwitched Brick Lining
Index:
A = Top layer of 50.8 mm Flat Brick (C.H.1:3)
B = A layer of (1:3) Red Cement Mortar 6.35 mm thick
C = 15.875 mm layer of (1:3) Red Cement Mortar
D = 50.8 mm thick Flat Brick layer with joints of Red Cement Mortar of proportion (1:3)
E = 9.525 mm thick Red Cement Mortar layer (1:5)
Indian Institute of Technology Madras
Hydraulics Prof. B.S. Thandaveswara
FLAGSTONE LINING 40 to 50 mm thick
on a bed of cement mortar 1:6 and
pointing with 1:3 cement mortar
TRANSVERSE SLEEPERS
.30 m centre to centre in
cement concrete 1:3:6
with 10 mm metal rod
100 MICRON LDPE
FILM AND GAUGE
20 mm THICK BEDDING
IN CEMENT MORTAR 1:6
FLAGSTONE LINING
LDPE 600/800/1000 Gauge
Brick lining 76.2 mm thick
in cement mortar 1:3
Dressed sub grade
Brick Lining
Indian Institute of Technology Madras
Hydraulics Prof. B.S. Thandaveswara
Tenax Mint 100
Composite membrane
as laid in profile
HDPE Membrane
30 mm thick concrete
size in flush point or
brick lining for
counter weight Geotextile filter
Graded soil slope
Tenax Mint 100
Composite liner Perforated drainage pipe
and Drainage wrapped in Geotextile
(Pressure relief drainage
with laminar drainage path)
SECTIONAL VIEW SHOWING DETAILS OF CANAL LINING
It has been ascertained through field seepage tests that lined canals save a
considerable amount of water loss as shown in Table
Percentages savings in
Average seepage loss water due to lining
State
m3/s/million sq.m compared with unlined
canal
Haryana
a) Unlined canal 2.25 -
b) Conventional lined canal
0.43 81
without LDPE film
c) Lined Canal with LDPE
0.16 93
film 2.5 mm
GUJARAT
a) Unlined Canal 2.50 -
b) Lined Canal without
1.00 60
LDPE film
c) Lined Canal with LDPE
0.80 68
film
Indian Institute of Technology Madras
Hydraulics Prof. B.S. Thandaveswara
WEST BENGAL
a) Unlined Canal
i) in rocky strata 2.94 -
ii) in lateritic strata 20.00 -
b) Conventional lined Canal
0.30 rocky strata 90
without LDPE film
c) Only LDPE film with soil
0.12 rocky strata 96
cover
Seepage studies - Ponding method Semi field Studies - KERS
Minimum value of
Sl. No. Type of lining material seepage after two years
in m3 / s / M m2
1 Tuflene with brick in cement mortar cover. 0.0008
2 Tuflene with earth cover. 0.0057
Tuflene with concrete cover (1 : 4 : 8
3 0.0008
proportion)
Before reconstruction 2.34 to 6.63 m3 / s / M m2
After reconstruction 1.53 m3 / s / M m2
LDPE 400 gauge (0.1 mm) Fibre glass Reinforced Plastic Tissue
LDPE 1000 gauge (0.25 mm) Reinforced asphaltic canal liner (2.5 kg / m2)
HMHDPE 700 gauge (0.1 mm)
Inspite of the advantages offered by conventional lining system with and without LDPE
film lining, they have several shortcomings. For example, in case of lined canals with
PCC concrete tiles as cover complete impermeability is not ensured as construction
joints are a must between two concrete panels, where the LDPE film below serves the
lining purpose. The ill achieved compaction of side slope of a canal in most cases give
rise to local shear failure due to lining overburden, with excessive slope settlement. In
such case of slope stability failure the unreinforced concrete slab cracks, consequently,
the unreinforced weak LDPE liner also gets damaged. LDPE membranes do not
possess suffficient strength and hence under sub grade reaction, or dead load and live
load on cover or hydrostatic pressure, the membrane gets ruptured on many occasions.
Under steep slope conditions and high flow discharge in the canal stringment reinforced
cover specifications are required which often makes the construction process of the
lined canal very tedious and time consuming.
Indian Institute of Technology Madras
Hydraulics Prof. B.S. Thandaveswara
Geo synthesis for Irrigation Structures
A wide range of Geo synthetic products find application in irrigation structures. They
include geo membrane, geo textiles, geo composites, geo grids, geo drains, gabions
and mattresses. Gabions are constructed using bi-oriented geo grids.
Geo synthetic Canal Lining and Drainage
As a fabric layer this system is extremely easy to install. The lining geo composites are
found in combinations of membrane-grid-textile, membrane-grid or grid-textile
sandwiches which can be used depending on the requirement of the project.
In case of the canal lining systems Geo composites having HDPE membrane-grid-
textile combination is the most suitable. HDPE membranes composites now available in
India, eliminates the shortcomings of the LDPE lined canal systems. The grid eliminates
the requirement of graded filter for drainage resulting in considerable reduction of time
and costs, increasing canal capacity of discharge. Drainage Geo nets, a few millimetres
thick have the same capacity of drainage water as a graded sand layer a few hundred
millimetres thick. The textile layer provided in these composites prevents the fines from
interfering with the drainage path. The Geo composites are used in canal lining system
with the water proof membrane in contact with the cover (required to weigh down the
geo composite on the slope) and the geo textile is laid against the well graded slope.
Geo composites are available in light weight roll form which can be easily laid on slopes
as well as on prepared canal beds. Geo composites have strength ranging from 6.5
kN/m to 23 kN/m which can adequately resist soil pressure on slopes and distribute
concentrated forces preventing local shear failure conditions from developing. The Geo
net with its high drainage capacity prevents high pore pressure development on the
slope and provides an efficient flow line.
Saving Geo synthetic lining vs Conventional lining 19%.
Reference
Som, S. Sarkar and Ranjana Majumder, Geo synthetic Reinforced Canal Systems and
Irrigation Structures, Proceedings Water Energy 2004, International R&D Conference
1995, New Delhi, India, pp 262 to 274.
Indian Institute of Technology Madras
