NDWI

The Normalized Difference Water Index (NDWI) is a very popular remote sensing index that is being utilized for water detection, water mapping, and water monitoring using satellite and aerial images. It is an index which is able to detect the presence of water bodies such as rivers, lakes, reservoirs, wetlands, and floods on the Earth's surface by assessing the spectral behavior of water at various wavelengths. The NDWI is normally based on the green and near-infrared (NIR) bands where the water tends to reflect green while absorbing NIR. The comparison between these two spectral bands enhances water and distinguishes it from vegetation, soil, and built-up.

This index is widely used in the GIS, remote sensing, environmental monitoring, hydrology, agriculture, flood mapping, land cover assessment, and many others. Time series analysis of NDWI is useful for the detection of the change in water extent because of seasonal variation, droughts, floods, reservoir operation, and climate change. The NDWI index can be derived from the datasets such as Sentinel-2, Landsat, and others, depending on the available spectral bands.