NANDINI MENON1 AND GRINSON GEORGE2
1Nansen Environmental Research Centre India
2 ICAR-Central Marine Fisheries Research Institute
State of Kerala is a strip of land with a coastline 590 km long
and width varying from 11 to 124 km.
Based on the geometry, geologic and geomorphic setting, the
Vembanad kayal is characterised by its long axes running
parallel to the coast (coastal plain formation of quaternary
period) and is separated from the sea by barrier spits
interrupted by tidal passes (Soman, 1997).
The large backwater extends from Munambam at north to
Alappuzha at south for a distance of 100 km on the south-
west coast of India (090 00’ – 100 40’ N Latitude and 760 00’ -
770 30’ E Longitude).
The width varies from a few hundred meters to 14 km.
Two rivers, Periyar and Muvattupuzha discharge into the
backwaters, whereas Thannirmukkom bund regulates the
flow from four rivers namely Meenachil, Manimala,
Achankovil and Pamba.
The bathymetry of the waterbody indicates that depth
variation occur between 1.5 m and 6.0 m in most parts
except the dredged channels, which are 13-15 m deep.
The sediments are a mixture of clay and silt (70–85%) and
The climate is typical of tropical features with monsoon (June–
September) yielding 60–65% of the total rainfall (approx. 300
The backwaters, a typical positive estuary houses the second
largest port along the west coast of India.
During monsoon season, heavy rainfall results in high river
discharge which results in less dense river water at surface and
high dense seawater at the bottom layers (salt-wedge).
In post monsoon, river discharge gradually diminishes and tidal
influence gains momentum and stratification weakens.
In pre-monsoon, river discharge is minimum and seawater
influence is maximum, the estuary is in a well mixed condition.
Development of turbidity maxima during high tide within the
estuary is very noticeable.
Northern parts of the estuary are subjected to higher salinity
wedging and oscillatory movement with vertical temperature
exchange than the southern parts.
With the installation of Thanneermukkom bund, stratification
is pronounced in the lower reaches of Periyar river (northern
parts of the estuary), while the southern parts appear to be well
Thottappally spillway, 20 km south of Alappuzha on NH-47, was
commissioned in 1955 to enable easier outflow of the combined
flood discharge from Pamba, Achencoil and Manimala rivers to
the sea. But it failed to bring in the desired results
•1.441 km long bund constructed in 1976 to prevent
salt intrusion into the low lying paddy fields of
•The bund is the southern boundary of Kochi
•Construction of Thaneermukkom Bund disrupted
water exchange transforming the southern part into
more or less a stagnant fresh water pool.
•The hydraulic barrier across the estuary has been
successful in preventing salt water intrusion and
increased sedimentation in the estuary.
•The progressive ecological degradation inflicted on
the entire estuary is severe
The tidal flux between riverine and estuarine
regions was affected by periodic opening and closure
of the Bund.
•The backwaters face serious
environmental threats by land
reclamation, expansion for
harbour development, dredging
activities, construction of dams
•Major changes began with the
construction of Cochin Port (1930-
1940) and reclamation of
•Reclamation has reduced carrying
capacity of Lake from 2.4 km3 to
•The Kochi backwaters has
suffered natural and man-made
shrinkages over the years, and its
mean depth has reduced to ~66%
during the past fifty years.
Vembanad lake supports as much biological
productivity and diversity as tropical rain forests.
Salinity controls the species composition and
succession of flora and fauna.
Phytoplankton ranges from typical marine form
Coscinodiscus sp. to fresh water form Cyclotella sp.
Nanoplankton is an important component in the
14 genera of freshwater phytoplankton were identified
during monsoon from the area.
Among zooplankton, the dominant forms are copepods (55-
The hydromedusa Eutima commensalis and the sergestid shrimp
Acetes cochinensis are endemic to Cochin backwaters.
Pre-monsoon brings in typical saline forms like chaetognaths
Low lying swamps and tidal creeks, dominated by sparse patches
of mangroves with their nutrient rich physical environment,
support larvae and juveniles of many economically important
Larvae and juveniles of commercially important prawns like F.
indicus, M. monoceros, M. dobsoni, M. affinis, Macrobrachium
rosenbergii are all found in the estuary.
Benthos represented by wood borers, biofoulers, bivalves, meio
and macro fauna, other crustaceans including prawns (Menon et
Black clam Villorita cyprinoidess
Effect of water quality degradation on fish diversity of
Many of the wild species of fishes which were previously available in
plenty is now extinct or rarely spotted and a few others are on the verge
of extinction(Vembanad fish count, ATREE, 2008-2011)
Vembanad Fish Count (VFC) conducted in May 2013 found that the
number of fish species decreased from 62 in previous year’s fish count to
58 species in 2013.
A steady decrease in number of Puntius was reported
Increased number of Tilapia has led to decrease in indigenous species
Fishing gears and traditional fishing operations are adversely affected by
the solid wastes and weeds in Vembanad lake.
Clogging of nets by masses of macroalgae and other plastic debris is
common. Most of the catches are discarded due to tainting and most
fishes smell and tastes kerosene.
Mud banks (CHAKARA)
Activity of longshore currents bringing in sediments into the
channels lead to the formation of mud banks.
Mud banks are regions of calm and highly turbid waters that
occur along certain parts of the Kerala coast during summer
monsoon season when the coastal region experiences high
The area offers fishing opportunity for fishermen during the
monsoon season when normal fishing activities become
difficult in rough weather.
The occurrence of mudbanks have come down drastically over
Even after several studies, the generation, sustenance,
dissipation and localisation of mud bank are yet to be
• Industrial area of Eloor with over 247 chemical industries such
as petrochemical, pesticide, rare earth elements, fertilizer, zinc
and heavy metal products is characterised as the ‘Pesticide
• Agricultural run-off result in high pesticide values (1.4 – 13.01
µg/l of Malathion) in Kuttanad region.
• Faecal coliform and biochemical oxygen demand of lake very
• Excess feed and fish waste discharged from the aquaculture
• Invasive and nuisance species of water plants. Pathogenic
bacteria and viral pollution (bacteria are antibiotic resistant).
• Radionuclides like Ra-228 and Ra-226 found in high
concentrations in the industrial zone. Source – fertilizer
• Decreasing fish yield. Fin fish diversity reduced from 50
species in 2008 (ATREE, 2008) to 42 in 2014.
• Based on the presence of indicator algal genera, Palmer
pollution index value was calculated. Palmer Index – 20 -
indicates organic pollution of the lake.
• Rapid industrialization and urbanization in the last few
decades resulted in discharge of about 1.04 x 105 m3 d-1 of
effluents and 260 m3 d-1 of sewage into the CE (Qasim 2003;
Balachandran et al. 2005)
• The level of coliforms in most of the stations of the study
region were above 1100/ 100ml.
•Kuttanad is a fragile wetland
eco-system; a delta covering
approximately an area of 1,100
•Area well known for its vast
paddy fields and geographical
peculiarities popularly known as
‘Rice Bowl of Kerala’.
•Area of reclaimed land,
separated by dykes from water
which is higher than it appears.
•The only place in the world
where farming is done up to 2
meters below sea level
•Rice cultivation has been the
•Kuttanad Package: Central
Government scheme where
funds are transferred based
on ‘project proposals’-
oriented to ‘water resources
The traditional agriculture known as pokkali
It is a rice- shrimp rotational cropping system.
These pokkali fields are highly productive
coastal wetland ecosystem which produces
enormous quantity of special variety of paddy
and palatable shrimp and fish depending on
Adjoining the 590 km long coast line there are
26000 ha saline paddy (pokkali) fields.
Paddy-cum fish/ prawn culture
Rice farms 1‐2 metres below sea level
A major problem for second crop is flooding of fields due to
breaches in the temporary bunds.
Salt tolerant strain of paddy cultivated in coastal areas for six
months from May to October.
Filtered shrimp or Prawn or fishes culture during November to April
under traditional farming system of about 12,986.6 ha in Kerala.
The major shrimp varieties are filtered during the entry process by
sluice gates and filtering net curtails the entry of unwanted species
into the culture system and also prevents the escape of cultured
species out of the system.
Rice cultivation alone not profitable under the organic farming, but
the overall Pokkali farming system is made highly profitable by
including prawn cultivation in the succeeding season
Pokkali rice farming is fastly approaching towards
extinction stage because of shortage of farm hands for
harvesting, increased weed problems, shift to
monoculture of prawn farming, and conversion of
fields for purposes such as roads, residential activities
Recommended a Pokkali rejuvenation Mission to save
the unique cultivation of paddy in saline waterlogged
lands in Ernakulam, Alappuzha, and Thrissur Districts
from extinction in the year 2012.
Pollution and Decline of prawn
Macrobrachium rosenbergii population in the estuary
Thanneermukkom bund which prevents the migration
of the juveniles into the brackish region of the estuary
is the major causative factor.
Along with it, the habitat destruction and pollution
are causative factors.
Fishery of Etroplus, the state fish of Kerala, has
progressed in the years, even after commissioning of
• Internationally well known tourist destination.
• God’s own country” one of the most important tourist
destinations in India.
• National Geographic Traveller: selected Kerala as one of the
“50 must see destinations in the world”.
• Some ~2000 houseboats operate in the area to serve the tourists.
• There are a number of tourist resorts nestling on its banks.
Vembanad bird sanctuary is located
at Kumarakom and Pathiramanal,
where a large number of tourists
congregate during October-March
every year – it being the peak
Contribution of houseboats in degrading the water
quality of the ecosystem
In case of Vembanad lake 80% of debris comes from land and rest 20%
comes from tourism related activities.
Solid waste, trash and other plastic wastes are discarded into the lake from
houseboats which are seen floating on water.
Majority of the houseboats release their sewage waste directly into the water
when they reach areas of fairly good water circulation like Thottapally.
Chronic discharge of solid wastes and sewage is seen also in parking areas
like Kavanttinkara, Cheepunkal, Punnamada contributing to the high
The cumulative effect of many boats discharging sewage proves to be more
harmful in this case.
Pathogenic contaminants such as Streptococci, faecal coliforms and other
bacteria cause infectious hepatitis, dysentery, diahorrea, skin diseases and in
extreme cases cholera and typhoid.
The minimum average area of each houseboat engine of 100 hp is estimated as 50
acres per boat (Rajan et al., 2011)
The usable lake area under the study is 90.31sq.km (based on GIS mapping)
Carrying Capacity = 501/180 = 2.78
Percentage at peak use = 501/180 *100 = 278%
= 90.31 Sq.km/50 = 180 boats
Only 180 houseboats are allowed to operate in the lake at a time
Estimated no: of houseboats at peak time = 501 (Port Trust data, 2012)
Recreational boat carrying capacity of the lake has exceeded the limits
and this exponential growth must be arrested or controlled to prevent
further destruction of lake caused by house boat operations.
Optimal boating density= Usable lake area/ optimum boating
Houseboats and resorts are one of the major factors contributing to the
degradation of Vembanad lake.
Low dissolved oxygen, high pH, high level of nutrients indicates the high
organic pollution in the lake
Plankton and fish diversity of the region has reduced considerably together
with the emergence of highly pollution resistant species.
Oil pollution is more alarming in areas of high houseboat activities. High
organic carbon in sediments renders the persistence of harmful PHCs in the
lake which are highly toxic to flora and fauna of the lake.
Carrying capacity of the lake has exceeded the limits and hence stringent
measures have to be adopted to regulate the houseboat activities in the lake.
Houseboat operations have adversely affected the socio-economic life of the
Ecosystem Health Index assessment reveals that the lake is under high
Dependence of community to
Fishing, duck-rearing, clam collection, toddy
tapping, canoe-making, water transporting, coir
weaving too have been the notable traditional
sources of livelihood.
Coastal Vulnerability CA
The coastal land up to 500 m from the High Tide
Line (HTL) and a stage of 100 m along banks of creeks,
estuaries, backwater and rivers subject to tidal
fluctuations, is called the Coastal Regulation
CRZ-1, CRZ 2, CRZ 3, CRZ 4.
Kerala is the only state for which violation mapping was
carried out throughout the coasts. Though Kerala has a
well-prepared CZM Plan, the State’s interest is to relax
the notification so as to accommodate the ‘development’
in the state.
Dependency Index Governance Index
Integrated Social & Natural Capital Index
Ability to GovernLow
HH / Census
LOW Governance Ability
LOW Governance Ability
CRZ I /
Coconut – husk – coir retting
The first coir factory was established in the ancient port
town of Alappuzha in the year 1859.
Household units are engaged in fibre extraction and
spinning of coir yarn throughout the coir producing
The industry employs about 7 lakhs of coir workers and
majority of them are from rural areas belonging to
economically weaker sections of the Society.
Women constitute 80% of the work force in the industry.
Coir retting and dyeing industry has led to serious
High values of hydrogen sulphide, ammonia, BOD
associated with anoxic conditions and low community
diversity of plankton, benthic fauna, fish, shell fish, wood
boring and fouling organisms were the outstanding feature
of the retting zones.
Banana cultivation and water
Banana cultivation-another major income.
Being a long duration crop, the total water-per year
requirements are high, varying between 1 200 mm in
the humid tropics to 2 200 in the dry tropics.
In the banana industry, water management practices
have significantly reduced its water footprint, defined
as the measure of the consumption and contamination
of freshwater resources for the production of a good or
Unregulated introduction and illegal
farming of several new exotic species has
been documented in the recent past. Several
of these species are listed as potential pests,
capable of negatively impacting the native
• Vembanad Lake has been characterised as one of the
most polluted water bodies in all India.
• In a list compiled by DST under its War for Water
Mission, Ernakulam and Alappuzha (the two main
administrative districts on the lake) have been identified
as key sites for study of the effect of biological
contamination on water quality in India.
• Coliform bacteria represent a major problem: the lake
serves as an aquatic reservoir for various water-borne
infectious diseases, including cholera and dengue.
Unscientific developmental activities have led to the
deterioration of water quality of Vembanad lake.
Interests of all sectors – agriculture, fishery, industry,
urban population – to be taken into consideration
when any reform is introduced or undone.
Unbridled tourism has to be curtailed.
Water stagnation in the lake to be resolved.