A review of water–energy nexus trend, methods, challenges and future prospects

The concept of water–energy nexus has gained global attention since the 2011 Bonn conference in Germany. Water–energy nexus thinking is critical because it supports various life forms on Earth, and its understanding can help in achieving sustainable development goals. In the present day, water and energy are closely intertwined, support and depend on each other for sustainable development in agriculture, urban settings and the industrial sector. Although the water–energy nexus still faces challenges of universal understanding, its adoption within the scientific community has been impressive over the past decades. Over 120 studies were reviewed in line with their aims, scopes, methods and limitations. About 23 case studies were summarized according to their title, objectives and major conclusions, while 21 case studies were cross-examined based on water–energy nexus studies within the urban systems. Models and methods use in water–energy nexus research were also reviewed with emphasis on their strength and weaknesses. The undisputable challenge within the water–energy nexus approach was found to be understanding, as concluded by almost all literature reviewed. Understanding the nexus approach and patterns is a huge limitation for the targeted audience, especially decision and policymakers. Bridging this knowledge gap between water–energy nexus scholars and decision or policymakers could lead to a significant breakthrough in the nexus arena. Another challenge faced by the water–energy nexus approach is the fact that though there are many methods currently employed, yet there is no single agreed or universally acceptable framework that could be used for the water–energy nexus studies globally. For a better understanding of the nexus thinking, more work in relation to understanding, framework and methods needs to be done in the water–energy nexus domain using a holistic approach. It is recommended that further analysis of the interlink ages of water–energy nexus can help mitigate the problem of understanding the system and hence support the sustainable development goals drive.