e - poz 2 - Central Institute of Brackishwater Aquaculture

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