Sasthamcotta is the largest fresh-water lake in Kerala. It caters to the drinking water need of Kollam town. Two other fresh water bodies, namely Chelurpola Kayal and Chittumala chira remain mostly unused. All these three fresh water bodies together account for an area of 6.80 sq.km. Detailed studies covering geology, geomorphology, hydrology, flora, fauna and socio-economic activities have been conducted.

It is found that at normal water level (0) the volume of water at Sasthamcotta will be to the tune of 13.95 million cubic meter (mcm). The other two lakes have 2.45 mcm at the same level. Detailed water budgeting of Sasthamcotta lake indicated that baseflow and aquifer recharge contribute 4.5 mcm. This indicates that sub-surface catchment area of the lake is much larger than the watershed area feeding the lake.

In view of this, a wider catchment within the Tertiary provenance, covering 66 sq.km area the surrounding fresh water bodies and portion of flood plains of Kallada has been considered for the study. Geologically, sediments of the warkali and recent formations dominate the area. Five geomorphic units have been identified. Presence of paleo channels adjoining the river within the flat terrain indicates shifting of river course. Around 60% of the area is under settlement with mixed tree crops. Paddy fields account for 23% of the area. Conversion of lowlands/paddy fields for non-agricultural purpose and reclamation of water bodies are recorded. There are 46 types of plants including trees, shrubs, herbs and climbers in this area. Sacred groves are also found. Quality of lake water is affected due to anthropogenic activities near the water bodies.

Management strategy of the area should address the issues of storage capacity enhancement, slope stabilisation, contour trenches & ridges, vegetative hedges as short-term activities. The long term activities cover conservation of floodplain, control of sand and clay mining, recharge enhancement, soil & moisture conservation, sanitation measures & retention of water quality. Maintenance of biodiversity, conservation of sacred groves and public awareness programme are also considered. This paper attempts to arrive at integrated lake management action plans for the larger catchment area based on specific results from the Sasthamcotta lake-catchment.

Centre for Earth Science Studies,
Trivandrum 695 031.Kerala, India.
Phone: 0471 - 442451
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