A geospatial study has found a considerable reduction in the area of Vellayani Lake, the second largest freshwater lake in the State. The report ‘Revive Vellayani – a geospatial perspective – facts and figures’ was released by Tourism Minister Kadakampally Surendran in connection with the launch of phase 2 of the Revive Vellayani project.
Conducted by the Swasthi Foundation, the preliminary study focussed on the Vellayani lake basin.
Satellite images
Recent satellite images and digital elevation models were used for the study, the parameters for which included land use land cover, physiography, slope, aspect, land form, topographic wetness index, stream network, drainage density, rainfall distribution, and so on. This helped correctly demarcate the lake’s boundaries, besides factors such as slope, wetness, drainage density connected with the lake.
The study found that from 1973 to 2019, there had been a considerable reduction in the area of the lake. In 1973, it was 558.93 hectares. In 1992, it had dwindled to 267.89 ha; in 2001 to 267.14 ha; and in 2011 to 243.39 ha. At present, the extent of the lake was only 222 ha.
The future of the biodiversity-rich lake was under threat from overfishing, excessive pesticide use, uncontrolled growth of lotus plants, use for irrigation, and encroachment.
Encroachment, the study said, was one of the main reasons for the decrease in the surface area of the lake from 558.93 ha to 220 ha.
As much as 42.18% of the lake basin was in the lowland region, whereas 57.82% was in the midland region, it said.
The study found encroachments in areas that have high topographic wetness index, which represents higher groundwater potential value. It highlights the need to preserve such areas.
The slope position class to helped identify ridges, flats, and valleys in the basis. In areas where the slope was low, the possibility of water content would be more.
The statistics on spatial distribution of all the thematic layers (parameters) would act as a base tool for the Indian Navy for the hydrographic survey of the lake that will help assess the dredging requirements of the lake.
The study was led by GIS expert Vinod P.G. and included S. Nalinakumar, S.R. Sreeraj, Adarsh Pratap, and Mohan Pillai.
