Monitoring Spatio-Temporal Changes in Surface Water Bodies in Gombe State, Nigeria Using Landsat and Sentinel-2 Imagery

Surface water resources in semi-arid environments are highly sensitive to climatic fluctuations and human activities, making long-term monitoring essential for sustainable management. This study evaluated multi-decadal surface water dynamics in Gombe State using satellite-derived Normalized Difference Water Index (NDWI) and Modified Normalized Difference Water Index (MNDWI) for the years 1987, 2005, 2015, and 2025. Multi-temporal satellite imagery was analyzed to quantify variations in spectral water reflectance and assess temporal trends over 38 years. The results reveal a non-linear pattern of surface water change. In 1987, moderate water presence was observed (NDWI max = 0.36; MNDWI max = 0.48), establishing a baseline condition. A significant increase occurred in 2005 (NDWI = 0.57; MNDWI = 0.96), indicating strengthened water reflectance likely associated with improved rainfall and runoff conditions. In 2015, NDWI declined to 0.30 while MNDWI remained high (0.98), suggesting continued water presence but reduced spectral intensity, possibly due to vegetation interference, turbidity, or seasonal variability. The strongest signal was recorded in 2025 (NDWI = 0.89; MNDWI = 0.99), reflecting substantial enhancement of surface water presence, potentially linked to intense rainfall or flooding events. Across all years, MNDWI demonstrated greater stability and sensitivity than NDWI, confirming its suitability for surface water detection in semi-arid regions. The findings highlight the dynamic and climate-responsive nature of surface water systems and underscore the importance of continuous satellite-based monitoring to support adaptive water resource planning, flood risk management, and drought preparedness in northeastern Nigeria.