This paper ascertains the costs and benefits of diverting water from the Senegal River. Two scenarios are compared to the status quo of inaction: the social planner and the competitive scenarios. Although these two scenarios yield positive present values of net benefits, the social planner scenario would use smaller quantities of water while providing the highest net benefits to society. Given that the benefits are one-sided while the costs are spread over several constituencies that share the river, it is possible for the gainers to compensate the losers, especially the farmers of flood recession agriculture identified as the main deprived group.