Characteristics and trends of hydrological droughts in Sub-Saharan Africa

This study on hydrological droughts in Sub-Saharan Africa offers a comprehensive narrative of their evolution, characteristics, and interconnections with meteorological droughts, crucial for understanding their complex dynamics and implications for water resource management and climate adaptation strategies. Hydrological droughts, characterized by prolonged periods of below-normal water availability, present significant challenges across Africa due to their extensive spatial and temporal impacts. The analysis relies on the African Database of Hydrometric Indices (ADHI), integrating streamflow data from 1466 gauging stations spanning 1951 to 2018. This dataset enables a nuanced exploration of hydrological drought trends, revealing distinct temporal patterns. A notable shift in drought characteristics around the 1980s is identified in the major part of the territory, with varying trends in drought duration and severity between the 1951-1980 and 1981-2014 periods. The findings suggest an increase in drought duration and severity in the earlier period followed by a decrease in the latter, marking a significant temporal transition. Spatially, the study identifies diverse patterns in drought occurrence and intensity across sub-Saharan Africa's hydrographic basins. Southern Africa exhibits higher frequency but shorter and less severe droughts compared to central and eastern regions, where droughts are less frequent but more prolonged and intense. These spatial variations reflect regional disparities in climatic conditions and basin characteristics, influencing how hydrological systems respond to rainfall variability. Furthermore, the study explores the complex relationship between meteorological and hydrological droughts. While meteorological droughts (SPI and SPEI) show varied trends, hydrological droughts generally mirror precipitation patterns, despite local variations due to local factors.