Cleaning of Canal System in Alappuzha Town Srikumar Chattopadhyay Centre for Earth Science Studies, Thiruvananthapuram
Cleaning of Canal System in Alappuzha Town
Sep 08, 2014
Cleaning of Canal System in Alappuzha Town by Srikumar Chattopadhyay Centre for Earth Science Studies, Thiruvananthapuram
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Cleaning of Canal System in Alappuzha Town
Srikumar ChattopadhyayCentre for Earth Science Studies,
Thiruvananthapuram
Why Cleaning Alappuzha Canals?
• Canal systems in Alappuzha town are degraded, utrificated, lost ecological functions and turned into environmental hazardous sites and carriers of urban wastes to Kuttanad area, rice bowl of Kerala
• To restore ecological functions of the canal so that ecological services (provisioning, regulating, cultural and supporting) are ensured for development of the society, both onsite and offsite
• To help ameliorate/ enhance land quality of parts of Kuttanad by improving water quality of the canals
Why cleaning Alappuzha canal
Weed infested canal
Stagnated water
No penetration of sun light
Nutrient enriched possibly through discharge of sewage and
Urban effluents
Polluted section of Vada canal
Vada canal lined on both sides. Water free of weeds but polluted
Why Cleaning canals?
Polluted waterLoss of organic life
Creates onsite and offsite problem
Restoration of ecological services
Regulating-Hydrological functionsProvisioning-Fishing, transport
Cultural-Aesthetic, tourism Supporting-Aquatic life,
How to clean?
• Measure-IMechanical removal of weeds and degraded organic materials-
Found not effective• Measure-II
Letting sea water inflow into the canal- Present proposal
Salient features of the project proposed by Irrigation Department,
Alappuzha• Installation of two iron pipes of 1m diameter and 150m into the
sea 1.2m below the sea level• Construction of a concrete chamber at Uppootti canal with
shutters to control sea water inflow into the canal system• Construction of another concrete chamber near NH bypass to
connect pipe lines linking sea in the west and the chamber in the Uppootti canal and regulated through a vulve
• Expected quantity of sea water inflow into the canal is 1.5m3/s in normal climatic conditions
• Water will enter into the canal by gravity flow and the system will be operated only during summer season
• There will be provision to drain out excess water in canal to the sea during rainy season
• There will be provision to maintain pipe lines in case of chocking by sand movement during monsoon
Recommendation of Technical Feasibility Study (CET, Thiruvananthapuram)
• With 1-0m diameter pipe, the discharge will be 2.75m3/s and the velocity of flow will be 5cm/s.
• With 1.5m diameter pipe, the discharge will be 6.89m3/s and the velocity of flow will be 12cm/s
• Proposed plan for sea water entry into the canal system is technically feasible and can be implemented, however physical modeling is required to assess sand deposits in the pipe system
EIA of Sea water inflow into the canal
• Impact of sea water inflow into the canal• Impact of salt water inflow on rice fields along
the eastern boundary where the canals are emptying into Kuttanad deltaic ecosystem
• Study is in two parts: (i) Understanding the larger settings and the canal system and (ii) Impacts
• EIA Method used: Rapid Impact Assessment Matrix (RIAM)
Understanding the system
• Physical parameters of canal• Water quality• Aquatic plants• Paddy fields along the eastern
boundary
AlappuzhaTown
Satellite view of Alappuzha town
and surroundings
Vembanadlake
Environmental settings of Alappuzha and surroundings
• Geologically recent landscape formed during last couple of thousand years
• Well known for mud bank formation in the sea side during monsoon months and thereby wave energy is moderated resulting promotion of fish aggregation
• Low lying sandy coastal ecosystem, bordered by clay belt (Kuttanad) along the eastern boundary
• Sandwiched between Lakshadweep sea and Vembanad lake • Interconnected canal system, drained through the Vembanad lake• Topography near flat, very gently sloping towards east • Once an important sea port served by water ways connecting
hinterlands through canals, rivers and back water systems• Shallow subsurface water • High population density [Alappuzha district is the most densely
populated (1489 persons/ sq. km) district in Kerala]
Monthly rainfall in Alappuzha
Average rainfall from 1995 to 2005
0.0
100.0
200.0
300.0
400.0
500.0
600.0
J F M A M J J LY A S O N D
Month
Ave
rag
e ra
infa
ll in
mm
Month Rainfall in mm% to total
rainfallJ 20.5 0.74F 31 1.13M 46.7 1.70A 156.3 5.67M 289.8 10.52J 542.2 19.68
JLY 433.4 15.73A 336.9 12.23S 291.9 10.60O 378.6 13.74N 168.8 6.13D 58.6 2.13
Total 2754.7 100
Average monthly rainfall (1995-2005)
State of Canal system in Alappuzha town
*Canals in Alappuzha town to serve as Three canals: Uppootti canal, Vada canal and Commercial canal
*Three cross canals connecting Vada canal and Commercial canal
*Average width: 17m to 20m, only Murinjipuzha canal is 8m wide
Canal system in Alappuzha town and its surroundings
Gradient of Commercial canal-0.011%Gradient of Vada canal-0.037%
Longitudinal Profile of Commercial Canal
-2
-1.5
-1
-0.5
0
0 1 2 3 4
Length (Km)
Dep
th (
m)
Longitudinal Profile of Vada Canal
-2.5
-2
-1.5
-1
-0.5
0
0 0.5 1 1.5 2 2.5 3
Lenth (Km)
Dep
th (
m)
C/S of Vada Canal West End
-1.4
-1.2
-1
-0.8
-0.6
-0.4
-0.2
0
0.2
0.4
0 5 10 15 20
Distance (m)
Dep
th (
m)
C/S of Vada Canal Middle Portion
-1
-0.5
0
0.5
0 2 4 6 8 10 12 14
Width (m)
Dep
th (
m)
C/S of Vada Canal East End
-2.5
-2
-1.5
-1
-0.5
0
0.5
0 5 10 15 20 25 30
Width
Dep
th
C/S of Uppootti Canal
-1.5
-1
-0.5
0
0.5
0 5 10 15 20 25
Width (m)
Dep
th (
m)
C/S of Commercial Canal West End
-1.5
-1
-0.5
0
0.5
0 2 4 6 8 10 12 14 16 18 20
Width (m)
Dep
th (
m)
C/S of Commercial Canal Middle Portion
-2
-1.5
-1
-0.5
0
0.5
0 2 4 6 8 10 12
Width (m)
Dep
th (
m)
C/S of Commercial Canal East End
-2
-1.5
-1
-0.5
0
0.5
0 2 4 6 8 10 12 14 16 18 20
Width (m)
Dep
th (
m)
Water quality analysis
• Quality of canal water has been compared with sea water and well water to understand present condition of the canals and expected quality improvement
• Well water was tested to assess linkage between well water and canal water
Commercial Canal-pH
0
1
2
3
4
5
6
7
8
9
2 4 5 6 7 9 10 12 11
Location
pH
Vada canal - pH
6.2
6.3
6.4
6.5
6.6
6.7
6.8
6.9
7
7.1
7.2
22 21 20 19 18 16 15 14 13
Location
pH
Well - pH
6.44
6.46
6.48
6.5
6.52
6.54
6.56
6.58
3 8 17Location
pH
Sea water - pH
0
1
2
3
4
5
6
7
8
9
1
Location
pH
Commercial canal Conductivity
0
500
1000
1500
2000
2500
2 4 5 6 7 9 10 12 11
Location
Co
nd
uct
ivit
y (
µS
/cm
)
Vada canal - Conductivity
0
100
200
300
400
500
600
700
800
900
22 21 20 19 18 16 15 14 13
Location
Co
nd
uct
ivit
y (µ
S/c
m)
Well - Conductivity
0
100
200
300
400
500
600
3 8 17
Location
Co
nd
uct
ivit
y (µ
S/c
m)
Sea water- Conductivity
0
10000
20000
30000
40000
50000
60000
1
Location
Co
nd
uct
ivit
y (
µS/c
)
Commercial Canal - DO
0
2
4
6
8
10
12
14
2 4 5 6 7 9 10 12 11
Location
DO
(m
g/l)
Vada canal - DO
0
0.5
1
1.5
2
2.5
3
3.5
4
22 21 20 19 18 16 15 14 13
Location
DO
(m
g/l)
Well - DO
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
3 8 17
Location
DO
(m
g/l)
Sea water - DO
0
1
2
3
4
5
6
7
8
1
Location
DO
(m
g/L
)
Commercial canal - Turbidity
0
10
20
30
40
50
60
2 4 5 6 7 9 10 12 11
Location
Tu
rbid
ity
(NT
U)
Vada canal - Turbidity
0
5
10
15
20
25
30
35
22 21 20 19 18 16 15 14 13
Location
Tu
rbid
ity
(NT
U)
Well - Turbidity
0
2
4
6
8
10
12
3 8 17
Location
Tu
rbid
ity
(NT
U)
Sea water - Turbidity
0
2
4
6
8
10
12
14
1
Location
Tu
rbid
ity
(NT
U)
Commercial canal - Salinity
0
0.2
0.4
0.6
0.8
1
1.2
2 4 5 6 7 9 10 12 11
Location
Sal
init
y (p
pt)
Vada canal - Salinity
0
0.02
0.04
0.06
0.08
0.1
0.12
0.14
0.16
0.18
0.2
22 21 20 19 18 16 15 14 13
Location
Sal
init
y (p
pt)
Well - Salinity
0
0.02
0.04
0.06
0.08
0.1
0.12
3 8 17
Location
Sa
linit
y (
pp
t)
Sea water - Salinity
0
5
10
15
20
25
30
35
1
Location
Sal
init
y (p
pt)
Commercial canal - TSS
0
5
10
15
20
25
30
35
40
45
50
2 4 5 6 7 9 10 12 11
Location
TS
S (
mg
/l)
Vada canal - TSS
0
20
40
60
80
100
120
22 21 20 19 18 16 15 14 13
Location
TS
S (
mg
/l)
Well - TSS
0
2
4
6
8
10
12
3 8 17
Location
TS
S (
mg
/l)
Sea water - TSS
0
20
40
60
80
100
120
140
160
180
1
Location
TS
S (
mg
/l)
Commercial canal - Hardness
0
50
100
150
200
250
300
350
400
450
2 4 5 6 7 9 10 12 11
Location
Har
dn
ess
(m
g/l)
Vada canal - Hardness
0
50
100
150
200
250
22 21 20 19 18 16 15 14 13
Location
Har
dn
ess
(mg
/l)
Well - Hardness
134
136
138
140
142
144
146
148
150
152
154
3 8 17
Location
Har
dn
ess
(mg
/l)
Sea water - Hardness
0
1000
2000
3000
4000
5000
6000
7000
1
Location
Ha
rdn
ess
(m
g/l)
Distribution of Hardness
Commercial canal - Ca
0
10
20
30
40
50
60
70
80
90
100
2 4 5 6 7 9 10 12 11
Location
Ca
(mg
/l)
Vada canal - Ca
0
10
20
30
40
50
60
70
80
90
22 21 20 19 18 16 15 14 13
Location
Ca
(mg
/l)
Well - Ca
0
10
20
30
40
50
60
3 8 17Location
Ca
(mg
/l)
Seawater - Ca
0
50
100
150
200
250
300
350
400
450
500
1
Location
Ca
(mg
/l)
Commercial canal - Mg
0
5
10
15
20
25
30
35
40
45
2 4 5 6 7 9 10 12 11
Location
Mg
(m
g/l)
Vada Canal - Mg
0
2
4
6
8
10
12
22 21 20 19 18 16 15 14 13
Location
Mg
(m
g/l)
Well - Mg
0
1
2
3
4
5
6
7
8
3 8 17
Location
Mg
(m
g/l)
Sea water - Mg
0
200
400
600
800
1000
1200
1400
1
Location
Mg
(m
g/l)
Commercial canal - Chloride
0
100
200
300
400
500
600
700
2 4 5 6 7 9 10 12 11
Location
Ch
lori
de
(mg
/l)
Vada canal - Chloride
0
20
40
60
80
100
120
22 21 20 19 18 16 15 14 13
Location
Ch
lori
de
(mg
/l)
Well - Chloride (mg/l)
0
10
20
30
40
50
60
70
3 8 17
Location
Ch
lori
de
(mg
/l)
Sea water - Chloride
0
2000
4000
6000
8000
10000
12000
14000
16000
18000
20000
1
Location
Ch
lori
de
(mg
/l)
Commercial canal - Alkalinity
0
50
100
150
200
250
2 4 5 6 7 9 10 12 11
Location
Alk
alin
ity
(mg
/l)
Vada canal - Alkalinity
0
50
100
150
200
250
22 21 20 19 18 16 15 14 13
Location
Alk
alin
ity
(mg
/l)
Well - Alkalinity
0
20
40
60
80
100
120
140
160
3 8 17
Location
Sea water - Alkalinity
0
20
40
60
80
100
120
1
Location
Alk
alin
ity
(mg
/l)
Commercial canal - PO4- P
0
200
400
600
800
1000
1200
1400
1600
1800
2 4 5 6 7 9 10 12 11
Location
PO
4- P
(m
g/l)
Vada canal - PO4- P
0
200
400
600
800
1000
1200
1400
22 21 20 19 18 16 15 14 13
Location
PO
4- P (
mg
/)l
Well - PO4- P
0
200
400
600
800
1000
1200
1400
1600
1800
2000
3 8 17Location
PO
4- P (
mg
/l)
Sea w ater - PO4- P
0
20
40
60
80
100
120
1
Location
PO
4- P
(m
g/L
)
Commercial canal - NO2- N
0
100
200
300
400
500
600
700
800
900
2 4 5 6 7 9 10 12 11
Location
NO
2- N (
µg/l)
Vada canal - NO2- N
0
5
10
15
20
25
30
22 21 20 19 18 16 15 14 13
Location
NO
2- N (
µg/l)
Well - NO2- N
0
10
20
30
40
50
60
3 8 17Location
NO
2- N (
µg/l)
Seawater - NO2- N
0
1
2
3
4
5
6
1
Location
NO
2- N
(µg
/l)
Commercial canal SO42-
0
10
20
30
40
50
60
70
80
90
2 4 5 6 7 9 10 12 11
Location
SO
42
- (m
g/l)
Vada canal - SO42-
0
2
4
6
8
10
12
14
16
18
20
22 21 20 19 18 16 15 14 13
Location
SO
42
- mg
/l
Well - SO42-
0
5
10
15
20
25
30
35
40
45
3 8 17
Location
SO
42
- (m
g/l)
Sea water -SO42-
0
100
200
300
400
500
600
700
800
900
1000
1
Location
SO
42
- (m
g/l
)
Crop calendar
0 30 60 90 120 150 180 210
1983-84
1984-85
1985-86
1986-87
1987-88
1988-89
1989-90
1990-91
1991-92
1992-93
1993-94
1994-95
1995-96
1996-97
1997-98
1998-99
1999-2000
2000-01
2001-02
2002-03
2003-04
2004-05
2005-06
2006-07
2007-08
2008-09
2009-10
December January February MayMarch April June July
Year Duration
2009-10 95
2008-09 98
2007-08 114
2006-07 104
2005-06 92
2004-05 952003-04 94
2002-03 90
2001-02 122
2000-01 130
1999-2000 118
1998-99 156
1997-98 132
1996-97 115
1995-96 122
1994-95 127
1993-94 121
1992-93 114
1991-92 124
1990-91 125
1989-90 121
1988-89 165
1987-88 147
1986-87 182
1985-86 166
1984-85 151
1983-84 181
Operation schedule of Thanneermukkom barrage across years
Movement of sea water
• MIKE 21 model was used to assess sea water inflow
• Sea water inflow of 1.5m3/s was considered• Scenario was created for simulated salinity
distribution at 6 hrs., 27hrs., 40 hrs., 69hrs., 99hrs.,105hrs., and at the end of 14 days
• Salinity propagation through Vada canal will take longer time than that through Commercial canal
Snap shot showing the simulated salinity distribution after 6 hours
Snap shot showing the simulated salinity distribution at 27 hours
Snap shot showing the simulated salinity distribution at 69 hours
Snap shot showing the simulated salinity distribution after 99 hours
Snap shot showing the simulated salinity distribution at 105 hours
Snap shot showing the simulated salinity distribution at the end of 14th day
Model
Impact of sea water inflow into the canal
• Physical and chemical: mixing of salt water and fresh water present in the canal, generation of water flow, wilting of aquatic plants, improvement of water quality, salinity intrusion in ground water
• Biological/ ecological: Brackish water ecology, improvement of brackish water aquatic lives
• Economic: Promotion of tourism and pisciculture, livelihood opportunities
• Sociological and cultural: Improvement of ambience, reduction of water borne disease
Impact of sea water inflow on Paddy fields
• Physical and chemical: Increase in salt content of adjoining canals, salt infestation of land, improvement of water quality in the canals around Padasekharams, presently carrying urban pollution, reduction of bacterial attack and improvement of land quality
• Biological/ ecological: Change of existing habitat• Economic: Cost involved in washing salt from paddy
fields, stress on summer crop if raised and loss of man days in case of crop failure
• Sociological and cultural: Farmers’ discontent in case of crop failure
Conclusions• Sea water inflow will restore the
canals• Sea water inflow should be
supplemented by control of urban sewage flow into the canal to restrict nutrient enrichment
• Model study indicated that salt water will reach to the eastern end.
• The crop calendar indicates that the fallow period is from end of March to May, sea water can be let in during this period. Operation of Thanneermukkom barrage can also be considered while deciding periods of sea water inflow through the canal system
• Pollution free water is required for sustaining humans, animals, crops and plants
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