Efficacy of the unmodified and modified water indices for saline wetland ecosystems

Abstract

Wetlands are world’s most significant, and diversified ecosystems, including an exclusive combination of water and land in both marine, and inland settings. Inland saline wetlands predominantly occur in arid and semi-arid regions of the world. Our study area the Sambhar Salt Lake is a halite-rich basin, which is India’s largest inland saline lake and situated in a semi-arid region, Eastern part of Thar Desert. Index methods are predominantly used for area change finding, and inspection purpose which split the water from its background on the basis of a threshold value. In this study we used 6 indices for surface area change detection of the lake from December 2018 and December 2021, for which we used Sentinel–2B data. We also analysed the physical parameters of water along with nitrate, and phosphate. The results showed decrease in concentration of EC, TDS, and salinity in 2018 to 2021 except pH. This may be due to rise in water level of the lake. Extracted surface water area increased in December 2021 compared to December 2018 by ~ 57 km2. This change in extracted surface water area reflects the human’s influence on lake. The NDWI index shows maximum area change ~ 13.35%. while overall best result was shown by AWEIsh and SWI indices. We found AWEIsh based algorithms achieved high accuracy 93.33% and kappa coefficient 0.9134 in compared to others. To conserve this highly deteriorating precious ecosystem there is need of proper monitoring and strict rules & regulation for its resources use.