Climate Change May Result in More Water Availability in Parts of the African Sahel

The African Sahel is known for its climate variability that often translates into recurrent droughts. Rainfall has drastically decreased substantially across the Sahel from the 1950s until at least the late 1980s. It is unclear from the literature and from the fifth IPCC assessment report whether the trend in annual rainfall in the next decades would be decreasing as observed throughout the century or increasing as suggested by a significant number of climate models. There is however a low to medium confidence that extreme rainfalls would increase. The objective of this paper is to demonstrate that both possibilities (an increase or a decrease in rainfall in the future) may results in more opportunities to mobilize water for populations in the Sahel. To demonstrate that, the ability of 20 regional climate models is evaluated based on their ability to reproduce key parameters of the rainy season in Niger, West Africa. The outputs of the 10 best models are then downscaled at 52 climate stations in the country to generate precipitation projections up to year 2100. Results show that a wetter climate is more likely than a drier climate at horizons 2021–2050, 2051–2075 and 2071–2100 compared to the 1979–2014 period; The paper also examines the so-called ‘Sahelian Paradox’, an observed counter-intuitive phenomena where decrease in rainfall resulted in a higher surface runoff, pointing to opportunities for water harvesting in the eventuality of a drier climate.