Monitoring water spread and aquatic vegetation using earth observational data for Nani-High Altitude Lake (N-HAL) of Uttarakhand State, India
Kishan Singh Rawat, Sudhir Kumar Singh
Abstract
The lakes are facing anthropogenic pressure and losing its characteristics. Hence, the evaluation of lake water quality is thrust area of research. The Nani-High Altitude Lake (N-HAL) was aimed to study during pre- and post-monsoon (March and October) period (2017 to 2022) using earth observation data based on false color composite (FCC) and spectral indices. The Sentinel-2 A/B data of 10 m spatial resolution was considered for monitoring and mapping of high-altitude lake. The FCC images were used to map and monitor changes in water spread and aquatic vegetation. Further, three spectral indices, namely, Normalized Difference Vegetation Index (NDVI), Normalized Difference Water Index (NDWI), and Normalized Difference Turbidity Index (NDTI), were applied to delineate water bodies and aquatic vegetation (Java moss, Amazon Sword, Java Fern, Anubia Nana, Crytopcoryne wendtii, Indian Waterweed, Pygmy Chain Sword, Rotala Rotundifolia, Hornwort, and Moneywort). Results reveal that the water surface extent has changed from 2017 to 2022, depending on the pre- and post-monsoon rainfall pattern during the study period. During a flood year on 18 October 2020–October 2021, in the area resulting into a drastic reduction in the aquatic vegetation and suspended particles. This lake needs immediate conservation and management policies.