Normalized Difference Water Index (NDWI)

"The NDWI index is most appropriate for water body mapping. The water body has strong absorbability and low radiation in the range from visible to infrared wavelengths. The index uses the green and Near Infra-red bands of remote sensing images based on this phenomenon. The NDWI can enhance the water information effectively in most cases. It is sensitive to built-up land and often results in over-estimated water bodies.

Values description: Values of water bodies are larger than 0.5. Vegetation has much smaller values, which results in distinguishing vegetation from water bodies easier. Built-up features have positive values between zero and 0.2." (Sinergise Ltd., n.y.)

NDWI = (Red - NIR) / (Red + NIR)
(Sinergise Ltd., n.y.)

Sources

"NDWI (Normalized Difference Water Index)". Seninel Hub,  Sinergise Ltd. N.y.
https://www.sentinel-hub.com/eoproducts/ndwi-normalized-difference-wate….
Accessed Mar 1, 2019.