Afroalpine Wetlands of the Bale Mountains, Ethiopia: Distribution, Dynamics, and Conceptual Flow Model

The Bale Mountains of Ethiopia contain the largest contiguous area of alpine habitat in Africa. The region provides critical water resources and other essential environmental services to highland communities, endemic wildlife, and millions of downstream people in East Africa. Increasing land use change has created concern over degradation to headwater wetlands and potential impacts on hydrologic regimes. Baseline understanding of wetland dynamics is lacking, however, and little is known about their function in the regional hydrologic system. We used remote sensing, machine learning, and field surveys to map the distribution of Afroalpine wetlands in the Bale Mountains. We developed a wetland typology based on hydrogeomorphic characteristics and a conceptual model of surface-groundwater flow. Our results show that wetland extent more than doubles between wet and dry seasons and that only 4 percent of the Afroalpine zone is saturated year-round. We also found evidence of a hydrologic continuum based on volcanic and glacial legacies, with wetlands at elevations above approximately 3,800 m asl likely to be ephemeral and wetlands at lower elevations tending to be perennial. Further interpretation suggests that local geology is a principal control on wetland distribution and hydrologic attenuation in the Bale Mountains. This lays the foundation for further research into surface-groundwater connectivity, climate change impacts, and conservation planning. Key Words: Afroalpine, Ethiopian highlands, HGM classification, mountain water tower, tropical alpine.