Spatial Shrinkage of Vembanad Lake, South West India during 1973-2015 using NDWI and MNDWI

Vembanad Lake is the largest estuarine- Lagoon system in Kerala. Considering its ecological significance and high biodiversity, it had been designated as the Ramsar site by the UNESCO in the Iranian city of Ramsar in 1981 and also classified as an Ecologically Sensitive Zone by the Ministry of Environment and Forests, India. In recent years, this estuary had undergone shrinkage due to various developmental and agricultural activities, which has been computed using remote sensing and GIS techniques coupled with field validation. A set of four Landsat satellite images that were acquired between 1973 and 2015 was employed to map the change in surface area of the Vembanad Lake using the water index methods. In the present study Normalised Difference Water Index (NDWI) and Modified Normalised Difference Water Index (MNDWI) methods were used to qualify the changes in the water area of the Vembanad Lake. The estuarine area were mapped using visual interpretation and ArcGIS 10.2.1 environment. The present study shows that the estuarine area is declining due industrial and agricultural developmental activities. The total shrinkage of the estuary during the study period was found to be 12.28sq. km (6.93 %).