Modeling Climate Change Impacts of Water Harvesting Practices in West Africa, Mali.

The West African county of Mali has a pressing need to develop agricultural adaptive practices that can increase its crop production in the event of future climate changes involving variable precipitation, high temperatures, and poor soil fertility. As an effort towards accomplishing this goal, a process based modeling approach employing APEX model was used to assess the impacts of traditional water conservation practices that can optimize soil water retention while alleviating soil fertility constraints for improved crop productivity under current and future climate change scenarios. A site in the Sahelian agro-ecoregion of Mali encompassing four soil types typically used for agricultural production was selected and future climatic scenarios for the years 2025–2035 and 2045–2055 were developed using two realizations from the MarkSim GCM daily climate simulator (IPSL and CSIRO sub models). Simulation of bunds, vegetative filter strips, contour ridges and planting pits (zai) were made to evaluate their effect on surface runoff, soil loss, and soil organic carbon and crop yields of maize, millet and sorghum. The performance of each water harvesting practice depends on the crop, soil type, slope, and climate scenario under which it is being used. Rainwater harvesting practices were generally not effective at improving maize or millet yields on very sandy arenosols, and/or under climatic scenarios with high annual precipitation (IPSL 2030). These practices were most effective at improving crop yield on more fertile lithosols and luvisols under climatic scenarios with low annual precipitation (CSIRO, 2050). Yield increases due to water harvesting practices were generally better with sorghum than maize or millet on all soils and under all climatic scenarios considered. Overall, contour ridges and zai improved crop yield more than bunds, which, in turn, were better than vegetated filter strips.