Abstract
West Africa is in general limited to rainfed agriculture. It lacks irrigation opportunities and technologies that are applied in many economically developed nations. A warming climate along with an increasing population and wealth has the potential to further strain the region’s potential to meet future food needs. In this study, we investigate West Africa’s hydrological potential to increase agricultural productivity through the implementation of large-scale water storage and irrigation. A 23-member ensemble of Regional Climate Models is applied to assess changes in hydrologically relevant variables under 2 °C and 1.5 °C global warming scenarios according to the UNFCCC 2015 Conference of Parties (COP 21) agreement. Changes in crop water demand, irrigation water need, water availability and the difference between water availability and irrigation water needs, here referred as basin potential, are presented for ten major river basins covering entire West Africa. Under the 2 °C scenario, crop water demand and irrigation water needs are projected to substantially increase with the largest changes in the Sahel and Gulf of Guinea respectively. At the same time, irrigation potential, which is directly controlled by the climate, is projected to decrease even in regions where water availability increases. This indicates that West African river basins will likely face severe freshwater shortages thus limiting sustainable agriculture. We conclude a general decline in the basin-scale irrigation potential in the event of large-scale irrigation development under 2 °C global warming. Reducing the warming to 1.5 °C decreases these impacts by as much as 50%, suggesting that the region of West Africa clearly benefits from efforts of enhanced mitigation.
Highlights
West Africa is in general limited to rainfed agriculture
In the 2 °C global warming scenario, warmer temperatures result in an average increase in Crop Water Demand (CWD) by up to 10% to 15% with respect to the reference period in all major West African river basins (Fig. 2)
It is worth noting that, CWD increases in both ETo formulations, that of Hamon generally simulates higher changes than that of Hargreaves due its higher known sensitivity to temperature changes38,39)
Summary
West Africa is in general limited to rainfed agriculture. It lacks irrigation opportunities and technologies that are applied in many economically developed nations. Irrigation potential, which is directly controlled by the climate, is projected to decrease even in regions where water availability increases This indicates that West African river basins will likely face severe freshwater shortages limiting sustainable agriculture. Regional climate models (RCMs) have had success in simulating and projecting climate change in West Africa[7,8,9,10,11,12,13,14] These studies tend to be uncoordinated in the sense that they consider different emissions pathways and different future and historical time periods. They tend to focus on changes of temperature and precipitation, and not to further variables that are relevant to water resources. Hypotheses of future GHG emissions pathways engender an additional level of uncertainty in the projections which is problematic of most of the GCM studies[15,16]
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