MSc

Lakes play the important role of storing the rain water and maintain the ground water table in the adjoining areas. They form a fragile ecosystem which reflect the nation’s ecological wealth. Lakes, in India cover 0.2 million ha. In Kerala, there are 10 fresh water lakes.
During the recent past, due to population pressure, vast areas of lakes and other wetlands have been filled and reclaimed either for human inhabitation or for agricultural activities, resulting in serious ecological changes. Vellayani lake, which is the only fresh water lake in Trivandrum represents one of the worst affected ecosystem in Kerala. Not much have been studied about the different ecological and pedological aspects of this lake. The present study was undertaken to throw light on the nature of land use and characteristics of Vellayani lake ecosystem, the production potential of the soil, and the extent of degradation of the lake ecosystem.
Nine locations were selected to represent both the Kayal lands as well the lands reclaimed by human activity. Profiles were taken from these locations and the samples were analysed for different physic – chemical characteristics. Water and soil samples were collected from the lake periodically and analysed for seasonal changes in pH, EC, chloride and sulphate. Climatological data of the station was also collected.
Results of the study prove that the lake ecosystem is fast degrading. Remote sensing techniques coupled with ground truth analysis have shown that 60% of the original lake area has been reclaimed. Due to heavy siltation, the average depth of the lake has been reduced to 3 m. Rainfall pattern of the location for a period of 11 years shows a drastic decline in the annual precipitation and the mean values has come down to 1520mm from 1840mm since 1982. Coconut is the predominant crop around the lake and the fringes of the lake have been reclaimed for different land uses. The predominance of crops in the reclaimed area are in the order rice, coconut, mixed trees, mixed crops, banana.
The water quality analysis has shown that the water is free from salts and can be safely used for domestic purposes as well for irrigation. The pedological investigations on the lake soil system indicated that the lake bed soil is of recent origin and belongs to acid hydomorphic group. According to U.S. Soil taxonomy it can be classified as fine. Kaolintic, isohypertheremic, acidic, tropic, fluvaquents. The lake bed is a highly productive soil system which can be better utilised for aquaculture rather than agriculture considering other ecological and environmental factors.
The step to abandon dewatering of the Kayal for cultivation has been a bold one from the part of the authorities and this coupled with other scientific conservation methods will prove a great deal in preserving this fragile ecosystem for future generations.