e - poz 2 - Central Institute of Brackishwater Aquaculture

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DHCRlPTlON OF THE VEMMNAD W EThe Vembanad lake spanning between latitudes 9' 28' and 10'10' N andlongitudes 76' 13' and 76" 31' E is the biggest among the 30 backwaters in theState. This has an area of about 22750 km' spread in to three districts, viz.,Emakulam in the north, Kottayam in the east and Alappuzha (Alleppey) in thesouth. The westem side is bordered by a narrow belt of land separating the lakefrom the Lakshadwip sea. It extends to a length of 96.5 km from Azhikode in thenonh to Alappuzha town in the south. The lake north of Aroor is situated in theerstwhile Cochin State, and is generally referred to as the Cochin backwaters. Thesouthern portion from Aroor to Alappuzha is more commonly referred to asVemba~d lake and lies in thc erstwhile Travawwe State. In strict terms, due toits continuity, both the water masses together constitute the Vembanad lake. Thelake is nadw and sinuous in the north while much broader to a maxumum of 14.5km in the south. In its length of over 96 km running parallel to the sea fromAzhikode to Alappuzha, the lake is mainly connected to sea only at two pldres,Azhikode and Kochi. Seasonal intrusion of seawater to the lake is also experiencedthrough the Thottappally spillway, situated 20 km south of Alappuzha. A smallconnection controlled through the spillway exists at Andhakaranazhi, in Ch~rthddltaluk, about 25km nbnh of Alappuzha town. It IS a complex system encompassingestuary, lagoons, marshes and mangroves with intricate network of natural andman-made channels.ORIGIN OF THE LAKE: The Vembanad lake is said to have or~g~nated arouncl5000-6000 years ago durlng the post glacial era when most of the world's coastalsystems took shape. However, according to the geolog~sts, the lake analned 1t5present configuration in the 4" century A. D. The system was primarily a marlneenvironment bound by an alluvial bar parallel to the coast line and interrupted bythe Arabian sea at intervals. As a result of the catastrophic deluge that took placein 1341 A. D., parts of Alleppey and Emakulam districts including a number ofislands thus separated into a distinct water body from the sea with connectingchannels at Thottappally, Andhakaranazhi and Cochin. During this period, theriver Periar emptying at Kodungallur took a diversion through Varappuzha ando p d into Cochin channel, giving rise'to a number of islands lying scattered inthe backwaters by the deposition of the alluvium in its course. This transformation
from the orig~nal marine environment into an estuarine environment is evident bythe large quantities of typically marine shells deposited in the Vembanad region.Thcs transformation has been well explained by Gopalan a/., 1983.The Vembanad lake lying in Kuttanad region is a low lying area near the coast ofthe Kerala. It was originally a part of the shallow coastal area of the Arabian sea.Consequent to geological uplift, a shallow bay was formed into which the riversdracnlng from the mountains to the east discharge. The coast was formed by thes~lt deposits carried by these rivers. The bay thus transformed into a brackishwater lagoon extending from Alappuzha in the south to Cochin in the North. In1976 the lagoon was separated into two by the construct~on of theltlanneermukkom barrier. The barrier was constructed to prevent sal~ne water~ntruslon Into the lake during the dry season (summer months) and also to retainthe fresh water from the rivers flowing into the lake. At the time of ~tsconstruction, the barrier was relatively successful in keeping water in Kundnadlresh arid thereby enabling cropping during the summer months. However, thebarrcer has had various adverse ecological.effects, which would be dealt in deta~lSHRINKAGE OF VEMBANAD LAKE: Backwaters have been cont~nuouslywblected to the reclamatcon for various purposes such as agrccultural expansionagrcculture pract~ces, harbour development, urban development and other publ~cand private uses A few hcstor~cal documents such as the Travancore LandRevenue Manual for the year 1834 testcfy that the local Government of the reglonhad encouraged large scale reclamatcon to the kayal lands (Travancore StateManual, 1834) Of the reclamat~on for the agrccultural purposes, paddy cult~vatlonand paddy-cum-shr~mp culture has contr~buted cmmensely to the horlzontdl5hrinkage of the backwater system In 1834 the Vembanad lake had an area ofnearly 365 km'. Accordcngly to P~lla~ and Pan~kkar (1965) dur~ng the early phases,land reclamat~on and flood control work were largely undertaken at the cnctlatlveof prcvatr farmen wcth actlve asststance from the State Government The detdllqon reclamatron of Vembanad lake for agrccultural and aquacultural purpose ISglven In Tablel. About 2,200 ha area have been recla~med tcll the begcnn~ng ofth~s century. Accord~ng to Kur~an (19781, the reclamatron actcvttles were banrred111 1903 as per the Government dcrect~ve so that ct d~d not h~nder Coch~nHarbour's development due to sclt accumulat~on. But later on, an area of 5,200 ha
Page 2 and 3: Ecology and Fisheries Investigation
Page 4: The Vembened take on the south-west
Page 7: The lakc had already been reclatd c
Page 11: of this century. The current lwei o
Page 14 and 15: The project was implemented partial
Page 16 and 17: The barrage at Thanneerrnukkom acro
Page 18 and 19: INvISTGATIONS ON THE FISHERY ECOLOG
Page 21 and 22: Several literatures are available o
Page 23 and 24: ECOLOGICAL INVESTffiATtONS WRING 19
Page 25 and 26: so.
Page 28 and 29: The sediment texture showed that sa
Page 31 and 32: summer. The pure saline forms that
Page 33 and 34: eporxd by Nair et al. (1983) was di
Page 35 and 36: lhJm md tabqodr Onty m spxlcr m6emd
Page 37: A view of the endangered fish speci
Page 41 and 42: Urcrobrachium rosenbergir 57 930 47
Page 43 and 44: The study reveals that the Thanneen
Page 45 and 46: BIBLIOGRAPHY ON VEMBANAD LAKEAnon.
Page 48 and 49: m,T.R. Mii(l. Y. nd Wli, C. M. 1984
Page 50 and 51: Smlathan, P., MccoJuMkr~y, N. I., r
Page 52: I. E-. Mu. bid. E d.I. lndln FWI. A

e - poz 2 - Central Institute of Brackishwater Aquaculture

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