High-resolution GRACE-based assessment of hydrological drought patterns and recovery dynamics across the Nile Basin countries (2003–2023)

Study Region:: The Nile Nations with its diverse hydrological and climatic conditions, from the Ethiopian Highlands to the Nile Delta, including major water bodies such as Lake Victoria and Lake Nasser. Study Focus:: We developed a comprehensive framework that allows drought monitoring in data-scarce regions by combining high-resolution GRACE terrestrial water storage downscaling with advanced spatiotemporal pattern recognition. Our approach employed Gaussian Process Regression to enhance GRACE data resolution from 400 km to ∼28 km, followed by the Joint Approximate Diagonalization of Eigenmatrices (JADE) algorithm to extract independent drought modes across the region. This pixel-level analysis quantified drought magnitude, duration, severity, and recovery dynamics from 2003–2023. The framework contributes in regional drought assessment by providing objective, spatially-explicit drought characterization without relying on sparse ground observations, offering a replicable methodology for other transboundary river systems. New Hydrological Insights for the Region:: Seven distinct drought hotspots were identified, including prolonged deficits in Lake Victoria Basin (2003–2013), severe drought in Lake Tanganyika region (2003–2006), and persistent water stress in the Ethiopian Highlands. Country-scale analysis revealed dramatic improvements in water security for Rwanda, Uganda, and Burundi post-2017, while east Egypt and Kenya continue facing persistent challenges. Recovery times varied significantly across regions, ranging from 4.3 months in Northwest Democratic Republic of Congo to 8.5 months in the Lake Nasser, which might provide insights for transboundary water management strategies.