Concept of a Geotechnical Solution to Address the Issues of Sea Water Intrusion in Ashtamudi Lake, Kerala

Abstract

This paper presents an innovative concept to transform brackish Ashtamudi Lake into a clean freshwater lake (partially or fully) using advanced geotechnology to construct a dike at appropriate place. This will serve two purposes: to meet water demands of the people and to save tiny islands from the threat of sea level rise. The sea level rise, according to researchers, is of serious concern in the state of Kerala which has a 590 km-long coastline and large expands of backwaters and estuaries and low-lying areas such as filtration ponds. Some tiny islands in Ashtamudi lake like Munroe Thuruthu islands seem to be gradually sinking due to reduced sediment deposits and sea-level rise. Nearby areas are facing frequent and increased tidal flooding throughout the year. The role of proposed project in saving these islands and other low lying areas from tidal flooding and sea level rise are discussed in the paper. Ashtamudi wetland is an estuary filled with brackish water and sewage, which lies in the Kollam district of Kerala. This study aims to conduct a comprehensive feasibility of the concept of conversion of brackish Ashtamudi Lake to a fresh water reservoir by building a barrage at the outlet of lake at the mouth of the Arabian Sea (Neendakara). On one side, it will block freshwater flowing from Kallada River to the lake from being discharged into the sea. On the other side, the barrage will prevent seawater from entering the lake, avoiding the adulteration of the freshwater supply with saltwater. This paper presents three different possible schemes to meet the water demands of Kollam city, Kollam district and entire state of Kerala. The paper also presents the required lengths of dikes for these schemes and suggest different methods of dike construction.