NDWI Annual Range

Land Usev0

Responsible:Niccolò Calandri

NDWI Annual Range

Overview

The NDWI Annual Range measures the pixel-wise difference between the maximum and minimum NDWI values recorded over a one-year period. This indicator captures the dynamics of water bodies and seasonal variations in water content.

Formula:

NDWI_range = NDWI_max − NDWI_min (pixel-wise, annual basis)

NDWI following McFeeters (1996):

NDWI = (Green − NIR) / (Green + NIR)

where Green = B3 (560 nm) and NIR = B8 (842 nm) from Sentinel-2.

Interpretation of values:

High range values (> 0.4) → strong water dynamics; seasonal lakes, flood-prone areas, wetlands
Moderate range values (0.2–0.4) → moderate water variation; riparian areas, seasonally irrigated zones
Low range values (< 0.2) → water stability; permanent water bodies, consistently arid areas

The indicator is useful for:

Identifying seasonal water bodies
Monitoring vegetation water stress
Assessing flood risk through historical variability
Supporting water resource management

Calculation Methodology

Dataset: Sentinel-2 Surface Reflectance Harmonized (ESA/Copernicus), bands B3 (Green, 560 nm) and B8 (NIR, 842 nm), resolution 10 m → 15 m.

Data acquisition — all Sentinel-2 images over the calendar year
Cloud masking — via SCL
NDWI calculation per image — NDWI = (B3 − B8) / (B3 + B8)
Pixel-wise max and min extraction
Range calculation — NDWI_range = NDWI_max − NDWI_min
Reprojection

Data Sources

Code	Name	Provider	Resolution	Availability
`WRD_S2XXX_99`	ESA Sentinel-2 L2A	ESA/Copernicus	10 m	2017-03-28 — present

Technical Notes

Sensitive to cloud-free scene availability and cloud shadows over water
In coastal areas, tidal variations may contribute to high range values
Dimensionless index, theoretical values between 0 and 2

References

McFeeters, S.K. (1996). Int. J. Remote Sensing, 17(7), pp. 1425–1432.
Xu, H. (2006). Int. J. Remote Sensing, 27(14), pp. 3025–3033.

Data Sources & References

Sources

WRD_S2XXX_99

Methodology

Il range dell'NDWI viene calcolato a partire dalle immagini Sentinel-2 Surface Reflectance Harmonized, utilizzando le bande B3 (Green, 560 nm) e B8 (NIR, 842 nm). Per ciascuna immagine disponibile nell'anno, viene calcolato l'NDWI = (B3 − B8) / (B3 + B8) dopo mascheramento cloud via SCL. Per ciascun pixel, vengono estratti i valori massimo e minimo dell'NDWI sull'anno, e il range è calcolato come differenza (NDWI_range = NDWI_max − NDWI_min). La risoluzione finale è di 15 metri.

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NDWI Annual Range

Land Usev0

Responsible:Niccolò Calandri