An explanation and quantification of the water-energy-food nexus (WEF-Nexus) is important to advance our understanding of regional resource management, which is presently in its infant stage. Evaluation of the current states, interconnections, and trends of WEF-Nexus, in cities, has largely been ignored due to quantification hurdles and the lack of available data. Based on the interaction of WEF-Nexus with population system, economic system, and environmental system, this paper builds the input output index system at the city level. Using the input output index system, we evaluate the WEF-Nexus input-output efficiency with the data envelopment analysis (DEA) model. We regard the decision making unit as a “black box”, to explore the states and trends of WEF-Nexus. In the empirical study based on data from China, we compare the input-output efficiency of WEF-Nexus in 30 provinces across China, from 2005 to 2014, to better understand their statues and trends of the input-output efficiency holistically. Together with the Malmquist index, factors leading to regional differences in the fluctuation of input-output efficiency are explored. Finally, we conclude that the DEA model indicates the regional consumption of WEF resources in the horizontal dimension and the trends in vertical dimension, together with the Malmquist index, to explain the variations for proposing specific implications.

Investing in human capital can assist in achieving technological innovations, while the spatial spillover effects of human capital on urban innovation in urban agglomeration are largely ignored. Using the panel data of 108 cities in China’s Yangtze River Economic Belt (YREB) during 2011–2020, this paper explores the interactions between human capital and urban innovation with a two-way fixed effects Spatial Durbin Model framework, which incorporates the interpretation of spatial spillover effects. The results show that urban innovation in the YREB has spatial heterogeneity in the structure, which is reflected in its diffusion from the downstream cities on the eastern coast to the upstream cities in the western region. Then, the low-level human capital inhibits the development of local innovation, while intermediate and high-level human capital improves local innovation. Furthermore, the spatial spillover effect shows an opposite trend. The impact of human capital on urban innovation is not significant in the downstream cities, such as Shanghai and Nanjing. Finally, three policy directions are proposed to optimize the human capital structure of the YREB, which are, strengthening investment in human capital and technological innovation, enhancing the talent spillover effect, and improving basic education.

Wastewater treatment and reuse are important means of addressing water scarcity and protecting the aquatic environment in urban areas. However, it comes at the cost of energy consumption and greenhouse gas emissions. However, the issues of governance and provincial-scale research have largely been ignored in current urban wastewater treatment and reuse studies. This paper summarizes the current status of 175 wastewater treatment plants (WWTPs) in Beijing, explores energy-intensive processes, energy consumption ratios, and the overall energy intensity of WWTPs, and maps the structure of urban wastewater treatment and reuse governance. The results indicate that most WWTPs in Beijing are medium or small in scale, treating wastewater at less than 200 thousand tons/day. Then, five energy-intensive subprocesses are identified, and their energy consumption ratios vary with treatment technologies and management factors, which calls for individual WWTP analysis and plant-specific strategies. The energy intensity of WWTPs in Beijing varies with treatment capacity and membrane bioreactor treatment technology used. Large-scale WWTPs employing MBR technology have a higher average energy intensity. Furthermore, the current coordination group and the four-layer policy system provide sufficient executive power and promote efficiency in departmental collaborations. Finally, inconsistent data, reductions in energy consumption, and the normalization of the governance structure are discussed, and policy suggestions are proposed.