A harmonized characterization of drainage units on the African continent

Integrated water resources management framework and other frameworks that approach sustainable resources management from a catchment perspective can benefit from the availability of a characterized and harmonized dataset of hydrological units. Harmonization is particularly relevant for a highly linguistically diverse continent such as Africa where high-resolution topographic relief datasets are not readily available, and most of the continent's waters fall within transboundary drainage units. This article describes and implements a hierarchical coding framework that harmonizes the description, classification, and coding of drainage units on the African continent. The continent is divided and subdivided into successively smaller drainage units, classified into six levels: systems, regions, subregions, basins, subbasins, and catchments, primarily determined by topology, location, type, and size of drainage units. Drainage units are consistently assigned identification codes that show their location and classification level. The classification groups the 1007 catchments (with areas ranging from 10,000 to 50,000 km2) on the mainland continent into 274 subbasins (50,000-250,000 km2), 119 basins (100,000-500,000 km2), and thirty-two subregions, twelve regions and five systems including islands. The characterization provides a high-resolution basin boundary dataset that improves data compatibility and accuracy and is expected to support catchment-based research and application on the continent.