Assessment of Colour Changes in Lonar Lake, Buldhana District, Maharashtra, India using Remote Sensing Data

Abstract

This communication presents results of a preliminary study to understand and assess the colour changes in Lonar lake, Buldhana district, Maharashtra, India, using remote sensing data of recent years (2019 and 2020). In addition, the study has utilized IMD gridded weather data and spectral profiles of algal pigments from the published literature. In order to verify whether the colour change is a cyclic event, long-term satellite data of Landsat 8-OLI and Sentinel 2-MSI sensors from 2014 onwards were analysed using spectral response in red and green bands. It was observed that even though a cyclic pattern exists, the colour change events occurred only during the 2019 and 2020 periods. The present analysis showed a change in colour of the lake from green to brown twice during April–June 2019. However, in 2020, there was a change in colour of the lake from green to brown and eventually to pinkish-red, which was not observed earlier. Rainfall and temperature were used to identify possible causes of abiotic stress on algae population of the lake. The study observed light rainfall and reduction in temperature just prior to the colour change event during both the years. In the absence of field data, the published literature on absorption spectra of different algal pigments was reviewed to identify pigments causing brown- and red-coloured appearance of the lake. Though cause of stress on the algae population is not known and is to be precisely identified by field surveys, the change in colour of Lonar lake appears to be caused by pigment(s), like phycoerythrin and carotenoids. However, this needs to be verified in the ground through water quality analysis.