DOI: 10.11648/j.ijsge.20261503.11 ISSN: 2575-1549

Temporal Dynamics of Normalized Difference Vegetation Index (NDVI) and Normalized Difference Water Index (NDWI) in Semi-Arid Gadarif Region, Sudan (1985–2024)

Ensaf Ahmed, Muna Ahmed
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Monitoring vegetation and hydrological dynamics in semi-arid ecosystems is critical for understanding responses to climate variability and anthropogenic pressures. This study employs multi-temporal Landsat satellite imagery (1985–2024) to examine spatiotemporal changes in the Normalized Difference Vegetation Index (NDVI) and Normalized Difference Water Index (NDWI) across three ecologically distinct localities—Al-Kayari, Alidedat, and Elsefia—within the Gadarif State, eastern Sudan. Image processing and spectral index computation were performed using Google Earth Engine (GEE) and ArcGIS Pro v3.4.0. NDVI analysis revealed a progressive increase in healthy vegetation cover (NDVI ≥ 0.3) in Elsefia (approximately 63 km 2 by 2024) and Alidedat (approximately 105 km 2 by 2024), indicating a positive greening trend over the study period. Conversely, Al-Kayari maintained comparatively drier conditions with persistently sparse vegetation. Parallel NDWI analysis demonstrated enhanced surface moisture and expanded flooded vegetation zones in Elsefia and Alidedat since the mid-1990s, while Al-Kayari continued to exhibit relatively low moisture availability. Pearson correlation analysis between NDVI and NDWI yielded a moderate positive coefficient (r = 0.63, R 2 = 0.40, p < 0.001), confirming coupled vegetation–moisture dynamics. These findings suggest a partial ecological recovery consistent with documented Sahel re-greening, potentially driven by rainfall variability, land use shifts, and hydrological feedbacks. The results provide a quantitative baseline for evidence-based land management, drought early warning, and climate adaptation planning in the semi-arid Gadarif region.

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