Water Use Trajectories in Agriculture and Hydropower in Zambezi River Basin: Assessing with Big Earth Data and Water-energy-food-environment Nexus Approach

Given the heightened competition for water in energy, food, and the environment in Africa, it is essential to implement sound integrated plans for basin or regional sustainable development. Zambezi River Basin (ZRB), one of the least developed basins in the world, is under development with great ambition for hydropower and irrigation infrastructure. Here, we proposed a framework to assess different water usage trajectories for agricultural and hydropower development scenarios with data derived from big earth data method . Three future scenarios were set for irrigaiton expansion and development hydropower construction according to current plan, global averagel and high level, respectively. Using spatial analysis methods, average evapotranspiration (ET) difference before and after irrigation expansion and reservoir construction was used to estimate water usage trajectories. Results show that the total available water resource for ZRB is estimated as 111.8 km³. Due to irrigation and reservoirs construction, additional annual water consumption is estimated to be 0.9 and 14.2 km³ for 2017, respectively. By analyzing the water-energy-food-environment (WEFE) nexus given water availability constraints, we found that the water development boundary in the ZRB could support increases in both irrigation proportion and dam density to global average levels of 20% and 0.56/10⁴ km², respectively, without degrading the environment. The proposed paradigm for assessing water resources has the potential to endow the ZRB with significant capacity to support the achievement of relevant Sustainable Development Goals (SDGs).