Evaluating 38 Years of Surface Water Change in Iraqi Lakes and Dams Using Landsat-Derived Normalized Difference Water Index (NDWI)

Abstract

Iraq’s surface water resources are under increasing pressure due to climate change, prolonged droughts, and upstream water management practices. This study aims to evaluate long-term changes in surface water extent across major Iraqi lakes and dams to understand hydrological trends over the past four decades. Using Landsat satellite imagery and the Normalised Difference Water Index (NDWI), we assessed surface water dynamics from 1986 to 2024 across six major water bodies: Mosul, Dokan, Darbandikhan, Hadithah, Razazza, and Tharthar. All analyses were performed in Google Earth Engine (GEE ) using annual NDWI composites and fixed water classification thresholds. Findings reveal significant surface water decline in Lake Razazza, which showed a strong and consistent decrease (R² = 0.86), and notable reductions in Tharthar and Hadithah. Mosul Dam experienced a smaller but clear downward trend, while Dokan and Darbandikhan remained relatively stable (R² = 0.05). Spatial change detection maps show extensive water loss in Razazza, Hadithah, and Tharthar, with minimal change in Mosul Dam. These results highlight the severity of hydrological stress in central and western Iraq and underscore the urgent need for sustainable water management, particularly under transboundary water constraints and shifting climatic conditions.