Hydrology, Ecology, and Pastoral Societies in the Sahel: Ephemeral and Perennial Water Resources in a Dynamic Coupled System

The grazing lands of the Sahel region of Africa are a vital grazing resource for the people of Africa, providing seasonal grazing for millions of animals. However, the region is subject to frequent droughts and considerable year-to-year uncertainty in availability of both fodder and surface water for cattle. Many small lakes in the region appear during the wet season but dry out during the dry season and, over millennia, human societies in the region responded to the seasonal availability of water for cattle by developing complex, socially-negotiated, long-distance herd-migration routes that organized and formalized access to the grazing resources of the Sahel. Since the droughts of the 1970s and 1980s the coupled hydrology and socioeconomic organization of the Sahel appears to be changing, with increasing drainage into pools that in some places now provide year-round water for cattle. This project will test the hypothesis that these system level changes were triggered by the drought which reduced vegetation cover and allowed increased water flows into pools. At a certain point, some lakes became deep enough to last through the dry season and, in some areas, the historically migratory communities responded by settling permanently near the lakes. A second hypothesis to be tested is that intense grazing activity now maintains a level of degradation and runoff in these watersheds that perpetuates the perennial lake state and permanent settlement. This project explores these complex interactions and feedbacks between climate, vegetation dynamics, landscape hydrology, and the human societies that depend on and manage these systems.

In Africa, the Sahel is a socio-economically vital region, important for livestock production but vulnerable to drought and famine. Increasing our knowledge of coupled human-natural system dynamics in the Sahel, including the processes that lead to rapid transitions in ecosystem and socioeconomic function, is vital to the wellbeing of vulnerable populations. This project will provide outreach to governmental, non-governmental, pastoral and agricultural communities in West Africa, expand university curriculum on coupled human and natural systems, and train graduate and undergraduate students. This project includes a significant international collaboration with researchers in Mali that is supported by funding from Office of International Science and Engineering's Africa, Near East, and South Asia program.