Water is the key limiting factor in socioeconomic and ecological development, but it is adversely affected by climate change. The novel virtual water (VW) concept and water, energy, food, biodiversity, and human health (WEFBH) nexus approach are powerful tools to assess the sustainability of a region through the lens of climate change. Climate change-related challenges and water are complex and intertwined. This paper analyzed the significant WEFBH sectors using the multicriteria decision-making (MCDM) and analytic hierarchy process (AHP) model. The AHP model demonstrated quantitative relationships among WEFBH nexus sustainability indicators in the Greater Horn of Africa countries. Besides, the net VW imports and water footprints of major staple crops were assessed. The composite WEFBH nexus indices varied from 0.10 to 0.14. The water footprint of crops is increasing period by period. The results also revealed that most countries in the study area are facing WEFBH domains unsustainability due to weak planning or improper management strategies. The strong policy constancy among the WEFBH sector is vital for dissociating the high-water consumption from crop production, energy, environmental, and human health system. Thus, this study enhances insights into the interdependencies, interconnectedness, and interactions of sectors thereby strengthening the coordination, complementarities, and synergies among them. To attain sustainable development, we urgently call all public and private entities to value the amount of VW used in their daily activities and design better policies on the complex WEFBH nexus and future climate change.

Complete water accounting (WA) and crop water productivity (CWP) analysis is crucial for evaluating water use efficiency (WUE). This study aims to evaluate the contributions of hydro-meteorological factors to the changes of WA and CWP and subsequent WUE based on the data from 2009–2020 in the Nile River Basin (NRB), East Africa (EA). The Mann-Kendall (MK) statistical test and Sen’s slope estimator were applied to detect the trends of climatic factors, and the AquaCrop model was used to simulate the crop yields in response to water balance and consumption based on crop physiological, soil water, and salt budget concepts. For the years 2012 and 2019, the mean of climatic water deficit P − ETa was 71.03 km³ and 37.03 km³, respectively, which was expected to rise to ~494.57 km³ by 2050. The results indicated that the basin water budget was unbalanced due to the coupled impact of year-to-year hot and dry conditions and increase in water abstraction, an indication of water deficit or stress. CWP and WUE increased during the study period with different changing patterns. CWP was also found to correlate to the yield of major crops (p-value > 0.05). It was concluded that climatic factors influenced the crop yield, CWP, and WUE in the study area. Thus, the improvement of CWP and WUE should rely on advanced water-saving innovations. The findings of this study could help water managers to improve water productivity by focusing on water account potentials and creating regional advantages by deploying water in combination with surplus flow from upstream to downstream consumption.