e - poz 2 - Central Institute of Brackishwater Aquaculture

The project was implemented partially. Only 62 shutters were erected at the westand east ends d the bamge. The central won was filled with earth. Theshutters were to prevent the salinity incursion to the southern sector during hight~des of November-December months, and were never intended to be closedpermanently. But, in effect, due to practical problems in intermittently openingand closing the shutters, the barrage mid closed permanently for about sixmonths from November-December to April-May. Only since 1992, the period ofclosure was reduced to four months, from December to April.The Thottappally spillway was also constructed, but with out the lead canal. As aresult, the floodwaters from the four rivers still continue to flood the paddy fieldsas before, occasionally with more severity. The Spillway and the barrage timeagain proved to be obstructions to the seaward flow, causing floods.Tidal flow cutoffConsequent to the commissioning of the barrage across the lake in 1976 and itsclosure during December to April end every year, the tidal inflow too remains cutoff to th~ sector. The result is a virtual stagnation of the water mass in the southernsector for virtually four months of the year. This has destroyed the continu~ty of theecosystem prohibiting the sharing of its physical and biological identity betweenboth the sectors. Faulty designing and partial implementation of the barrageproject had brought with it unanticipated misfortunes. The most discerntbleamong them was a virtual stagnation of water mass in the southern sector and itsadloin~ng canals and water ways during the summer, resulting in serious pollutionand health hazards in the area.With respect to the morphological features, the investigation under the presentprojea has revealed the prominent timexale changes in the southern sector of thelake. The ecological transfonnation in the seaor from the estuarine phsse to analmost freshwater phase resulted in a qualitative and quantitative change in thebiota of the severed aquatic environment. The most apparent change was in thefish fauna. The less noticed but significant changes were among the smallercommunities such as plankton and benthic organisms. The water and sediment