This layer maps the change in water turbidity of a water body between two annual periods, computed from the Normalized Difference Turbidity Index (NDTI = (B4 - B3) / (B4 + B3)) on Sentinel-2 imagery (COPERNICUS/S2_SR_HARMONIZED) at 10 m resolution over water pixels only. The value is the difference between the final-period NDTI composite and the initial-period NDTI composite. Positive values (warm colours) indicate increasing turbidity (more suspended particles, reduced water clarity), while negative values (cool colours) indicate clearer water.
This layer quantifies how water turbidity has changed between two annual periods, using the Normalized Difference Turbidity Index (NDTI) derived from Sentinel-2 surface reflectance. NDTI exploits the contrast between the Red and Green bands, which increases as suspended particles scatter more light. The analysis is restricted to water pixels (land is masked) and clouds are masked before compositing.
| Code | Provider | Resolution | Year |
|---|---|---|---|
| WRD_SCLXX_99 | ESA / Copernicus (Sentinel-2, COPERNICUS/S2_SR_HARMONIZED) | 10 m | 2017 to present |
For each of the two periods a cloud-free, water-only NDTI composite is built as NDTI = (B4 - B3) / (B4 + B3), where B4 is Red (665 nm) and B3 is Green (560 nm). The delta layer is the pixel-wise subtraction of the initial-period composite from the final-period composite (final minus initial); positive values indicate increased turbidity and negative values indicate clearer water. Sentinel-2 data are available from April 2017 onward; the base processing scale is 10 m and is adapted upward (20 m or 25 m) for very large areas.