WI – Water Index

3. Google Earth Engine Code (WI)

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// ----------------------------
// WI (Water Index) – Sentinel-2
// ----------------------------

// 1. ROI (draw directly in the editor)
var roi = geometry;

// 2. Load Sentinel-2 SR
var s2 = ee.ImageCollection("COPERNICUS/S2_SR")
  .filterBounds(roi)
  .filterDate("2023-01-01", "2023-12-31")
  .filter(ee.Filter.lt("CLOUDY_PIXEL_PERCENTAGE", 20))
  .median()
  .clip(roi);

// 3. Compute WI
var wi = s2.expression(
  "(GREEN / NIR)",
  {
    GREEN: s2.select('B3'),
    NIR: s2.select('B8')
  }
).rename("WI");

// 4. Visualization
var wiVis = {
  min: 0,
  max: 3,
  palette: ['#440154', '#31688e', '#35b779', '#fde725']
};

// Add to map
Map.centerObject(roi, 10);
Map.addLayer(wi, wiVis, "WI");

// 5. Export
Export.image.toDrive({
  image: wi,
  description: "WI_Export",
  fileNamePrefix: "WI",
  scale: 10,
  region: roi
});