Normalized Difference Water Index (NDWI) may refer to one of at least two remote sensing-derived indexes related to liquid water:
One is used to monitor changes in water content of leaves, using near-infrared (NIR) and short-wave infrared (SWIR) wavelengths, proposed by Gao in 1996.
Another is used to monitor changes related to water content in water bodies, using green and NIR wavelengths, defined by McFeeters (1996).
NDWI of Rome. Acquired on 8.10.2017.