Impact of Climate Change and Land Use Cover Change on the Water-Energy-Food Nexus in West Africa

Abstract

The dynamic interaction between climate and land plays an important role in water, hydropower, and food production in West Africa (WA). However, the interaction between climate, land, and water is oversimplified in RCMs, leading to inaccurate predictions of the timing and availability of water resources. Moreover, most hydrological models’ approach to resource management is water-centric based on IWRM frameworks but lacks a strong basis for WEF nexus studies. Furthermore, there is little research to understand the effects of deforestation and afforestation on the local water-food nexus. The first objective of this thesis aims to characterize the relationship between climate variability and land use/land cover change in WA using remote sensing and reanalysis products. The second objective aims to model the relationship between climate variability and land use/land cover change using the WRF-Hydro model. The third objective aims to assess the future impacts of climate change, land use and land cover change, and population growth on the WEF nexus components. Objective one (1) was achieved by analyzing climatic and land cover changes in West Africa. Objective two (2) was achieved by modeling the effects of afforestation and deforestation on the climatological water flow change in the SKB. Objective three (3) was achieved by building a Volta-WEF nexus to quantify future water and hydropower availability indices. The NSE and KGE of WRF-Hydro setup is 0.47 and 0.69, respectively, over the KB compared to the default setup values of -0.34 and 0.2. The Volta-WEF model in WEAP yielded an R2 (NSE) of 0.74–0.85 (0.71–0.79) and 0.7–0.81 (0.66–0.81), respectively, over the calibration and validation periods. Over the 1992–2019 period, an interannual temperature change of 1.0 to 2.0 ℃, and a 50 mm change of precipitation and climatic water balance resulted in 20935–52133 km2 land cover change intensities, while a temperature change of 0.5 ℃ and a precipitation change of 20 mm represented normal climatic conditions with land cover change intensities below 20000 km2. The afforestation experiment yielded approximately 6% more precipitation, 3% more evapotranspiration, 27% more surface runoff, and 16% more underground runoff, while the deforestation experiment yielded 5% less precipitation, 3% less evapotranspiration, 3% less surface runoff, and 9% less underground runoff over the SKB. The future water demand index is estimated at 0.94 to 0.96 for SSP1-2.6 to SSP5-8.5 and the future hydropower generation index is between 1.001 and 1.002 for all SSPs, illustrating the water-energy nexus. Future works can consider implementing the climate-land relationship described in this work into RCMs. Moreover, staple crops could be included in the WEF-Volta model to account for food production.