06-bioresourcesstatu.. - M. S. Swaminathan Research Foundation

Impact of Thottappally spillway and
Thanneermukkam salt water barrier on paddy
production works and Fishery:
The problems created by these two structures
were manifold, some of.them being:
i) The present flood discharge through the
Thottappally spillway is only 1/3rd of what
was designed for. Hence, flooding of paddy
fields continued.
Ii) Once the rainy season is over, the shutters of
Thanneermukkam salt barrier are lowered to
prevent the entry of salt water. This coupled
with excessive evaporation and meagre flow of
river results in insufficient water flow in the
lakes eyen rendering boating difficult.
Appendix - 1.
iii) The relting of coir fibre is poor due to the
absence of tidal influence.
iv) Area for foraging for the larvae of marine
prawns, which was reduced due to
reclamation, was further reduced due to
closure of sluice gates by the salt-water
barrier.
v) As there is no flow of water, the inlet of sea
opposite the Thotlapally spillway is blocked by
a sand bar.
vi) Lowering of the Thanneermukkam shutters
resulted in flooding of north of the barrier.
vii) As there was no flushing of water, major area
of the southern part of the lake was covered
by African payal Salvinia moresta.
viii)Acid levels increased to lethal levels killing
the clam Vellorita cyprinoids which is the
only source of lime in the state. Acidity also
increased the copepod infestation on the gills
of fishes.
ix) After monsoon, the shutters are raised
resulting in surging of salt water. As the fishes.
get very little time for acclimatization, mass
mortality occurs.
x) Pollution from coconut husk retting results in
mosquito menace in stilI water.
iii. Threats to local dependent population
The local population is very much dependent on
the fishery resources of the lake. The most prized
catch is the giant freshwater prawn - M.
msenbergii. However, the decline in most of the
fish catch in general and M. rosenbergii in
99
Vembanad Lake
particular has affected economy of the local
population severely.
VII. Conservation and Management Efforts
LApplicable Protection Act
Coastal regulation zone notification of 1991 is
applicable in Vembanad Lake and adjacent areas
ii. Government Agencies
The Department of Fisheries, Kerala State in
collaboration with Fishermen Co-operative
Societies of the state is monitoring ban during
monsoon. Tourism industry is well developed in
Kerala. Due to the problems lingering in Kashmir.
tourists are attracted to backwaters of Kerala,
which provides an excellent house boating
facilities.
iii. Non Government Agencies
Many of the mangrove vegetation of Kerala are
under threat. From a total area of 70,000 ha,
vegetation is reduced to about 5,000 hectare.
Many of these areas are under village panchayat
or local bodies.
iv. Local communities
The local communities have a very high degree of
awareness and they are not benefited by the
construction of the salt barrier. The consequent
reduction of catch and mangrove and the damage
to the ecosystem is well documented. The local
communities in collaboration with the government
and non-government agencies are willing to
restore the pristine glory.
v. Other Institutions
Fishers co-operative societies, Federation of
fishermlln societies, Universities and other
educational/research institutes are contributing
towards its development and restoration.
VIII. Future Prospects
The Vernban ad Lake along with its confluent a
lucrative fishery during the 1950's & 1960's. The
giant freshwater shrimp became a big foreign
export earner of the state from the inland side.
However,with the commissioning of salinity barrier
in 1976, which divided the lake into two entirely
different types of water, bodies completely changed
the ecology of the area. Coupled with the barrier
construction was the reduction of water spread
and pollution from industries dealing in pesticides,