Overview of the Methodology Developments in Water-Energy Nexus Studies

Water and energy are the most critical resources for human society development and are also the essential sources of significant environmental issues when not properly managed or utilised. Systematic analysis of the two elements facilitates the overall optimisation of water and energy utilisation, rather than decreasing one while increasing another. The concept of the water-energy nexus, namely the interlinkages between water and energy, has been well accepted and utilised in water-energy resource assessment. Various studies have been carried out under this topic and trying to interpret the linkages and use this linkage to assess resource utilisation performance. This review aims to provide a clear vision and possible future directions for implementing and improving water-energy nexus research. The water-energy nexus assessment methods reported in the literature include conceptual framework, statistical analysis, indicator-based approach, and mathematical modelling. Key findings of the review include: 1) The need for more awareness and understanding of the nexus and improve the assessment from quantification to a designing tool. 2) Data availability and quality are still a great challenge for current studies, and data validation is missing in many studies. 3) The water-energy nexus assessment covers mainly the quantity of the flow. In contrast, the quality of the flow is mainly neglected, and 4) the functional unit of water-energy should be further investigated and using monetary units can be a feasible solution.