Interrelations between the water, energy and food systems and climate change impacts in the Zambezi River Basin

The WHAT-IF model was applied to Southern Africa to investigate the impact of climate change and variability on water infrastructure investment planning for the Zambezi River Basin. Zambezi water investment decisions are linked with the climate change impacts on the regional rainfed agricultural system of Southern Africa and electric generating system of the Southern African Power Pool. Climate change will have significant impact on streamflow, rainfed crops and will impact hydropower production. To address the uncertainty about future climates we examine four emissions scenarios with 7,200 climates each while overlaying 100 spatially- and temporally consistent weathers for each climate, capturing the full range of both uncertainty and variability. Trade-offs between agriculture, hydropower and ecosystems are limited under the current climate. Assuming irrigation is developed, those trade-offs increase significantly with climate change. Enforcing more ecosystem conservation policies would principally affect hydropower production but could also affect irrigated agriculture under the driest climate change scenarios. Under severe climate change impacts, ignoring water needs for ecosystems could lead to underestimating water constraints for irrigation. Result show that considering the inter-annual climate variability is even more important than climate change trends. For the region, the effect of climate on crop yields and hydropower production in extreme years is much more than the effect in average years. This suggests the need to better account for such weather events in investment planning.