NDWI detects water bodies and moisture content in vegetation using satellite data. Water reflects more green light and absorbs near-infrared (NIR) light. 

• Formula: NDWI = (Green - NIR) / (Green + NIR) 

• Range:
  +0.5 to +1.0 → Water bodies
  0 to +0.5 → Moist vegetation or wet soil
  Negative values → Dry vegetation, bare land, or urban areas

• Data Source:
  Based on Landsat 5, 7, 8, and 9 imagery (NASA & USGS) processed in Google Earth Engine for 1990–2024.