The Normalized Difference Water Index (NDWI) is a spectral index designed to enhance the presence of water features in remotely sensed imagery while suppressing noise from built‑up areas and vegetation. By exploiting the contrasting reflectance of water in the green and near‑infrared (NIR) portions of the electromagnetic spectrum, NDWI provides a simple yet powerful tool for hydrological mapping.
Water absorbs strongly in the NIR region but reflects relatively more in the green band. Conversely, healthy vegetation reflects strongly in NIR and less in green. The NDWI therefore creates a normalized ratio that highlights water bodies (positive values) and diminishes vegetation and soil (negative or near‑zero values).
Because the index is normalized, it is less sensitive to illumination differences, sensor calibration, and atmospheric effects, making it suitable for multi‑temporal analyses such as flood monitoring, wetland delineation, and drought assessment.
What is NDWI used for?
How does NDWI work?
What bands are used in NDWI calculation?
Why is NDWI useful for hydrological mapping?
Can NDWI be used in urban planning?
What is the formula for calculating NDWI?
Results are for informational purposes only and do not constitute professional advice.