Water stress assessment integrated with virtual water trade and physical transfer water: A case study of Beijing, China

Exploring the coupling coordination relationship of water resources, socio-economy and eco-environment in China

Water resources (W), socio-economy (S), and eco-environment (E) have incredibly intricate linkages of interaction, and the coordination of them is crucial to the long-term sustainability of a nation. Thus, we considered "water resources, socio-economy, and eco-environment" (W-S-E) as a composite system and constructed an evaluation model to quantitatively analyze the coupling coordination degree (CCD) of W-S-E system in China from 2011 to 2020. Then, the spatial correlation characteristics were analyzed by using spatial autocorrelation method. To analyze the time evolution patterns of the W-S-E system, this paper divided the stages from the perspective of clustering, which is more scientific and interpretable than the CCD fixed-value division. We found that: (1) W subsystem, S subsystem and E subsystem were closely connected and its CCD was enhanced with relatively higher growth rates in the development of S subsystem but slower growth rates in the W subsystem. (2) The CCD of W-S-E system had spatial correlation. The areas with low CCD were concentrated in the west of China, forming poor coordinated development phenomena. Conversely, most of provinces had relatively high CCD in the east of China with the coastal region playing radiative driving function. (3) The temporal change of W-S-E system followed four transforming patterns including "policy-oriented type", "resource problems constraint type", "socio-economy leading type", and "special location controlling type". Furthermore, we also put forward some advice and policy suggestions. The findings provide research basis and guidance for the sustainable and coordinated development of water, society and ecology.

Hysteresis response of groundwater depth on the influencing factors using an explainable learning model framework with Shapley values

Machine learning has been widely used for groundwater prediction. However, the hysteresis response of groundwater depth (GD) to input features has not been fully investigated. This study uses an interpretation method to reveal the interplay between climate, human activity, and GD while considering the response of groundwater to multiple factors. Six factors [precipitation (P), wind speed (WS), temperature (T), population (POP), gross domestic product (GDP), and effective irrigated area (EIA)] were selected to analyze the hysteresis response of GD in terms of the lag correlation coefficient and lag time. The correlation between climatic variables and GD was weaker than that of anthropogenic variables. The lag time between variables and different types of GD was less than four months at most sites, except for EIA and WS in deep groundwater. The SVM model achieved satisfactory performance in 89 % of the sites. If there were sharp changes in GD during the testing period or significant variations in its seasonal patterns at different times, the SVM model performed poorly. The model was interpreted using the Shapley additive explanation method. The impact of POP and GDP on deep groundwater in irrigated areas was higher than that of shallow groundwater. In urban areas with intensive human activities, anthropogenic variables were the main factors affecting shallow groundwater while the impact of climate was gradually increasing in the suburbs. The influence of precipitation on shallow groundwater was decreased after water transfer from the South-to-North Water Diversion project. Furthermore, this study proposed a multifactor-driven conceptual model that can provide recommendations for analyzing groundwater dynamics in similar areas.

Research on the association of China-US virtual water trade based on hypothesis extraction method

Based on the EORA input-output tables from 2006 to 2016, this paper divided 189 countries in the world into three economies (China, the USA, and other countries) and used the hypothetical extraction method to calculate the virtual water trade volume of the three economies in the Sino-US bilateral trade. Combining with the analysis of the global value chain, the following conclusions were drawn: (1) the virtual water trade volume exported by China and the USA showed an overall increasing trend. The virtual water trade volume exported by the USA was far less than that of China, but more virtual water was transferred through trade. (2) Compared with intermediate products, China's virtual water exports of final products were larger, but the USA was the opposite. (3) Among the three major industrial sectors, the secondary sector was the largest virtual water export sector in China, but it was the primary sector in the USA that had the largest volume of. (4) Bilateral trade had brought environmental disadvantages to China, but this situation was gradually improving.

The Temporal Evolution of Physical Water Consumption and Virtual Water Flow in Beijing, China

With the rapid development of the socio-economic system and the close connection of inter-regional trade, the physical water consumption in production and the virtual water flow associated with inter-regional trade are both have a significant impact on local water systems, especially in megacities. Beijing is the political, economic and cultural center of China, which is a megacity that has severe water scarcity. To evaluate the status-quo of local water consumption and propose the countermeasures, this study quantitatively analyzed the evolution trend of physical water consumption and the virtual water flow in Beijing. The results show that the total physical water consumption in Beijing decreased from 2.43 billion m3 (2002) to 1.98 billion m3 (2017), while the net virtual water input increased from 1.76 billion m3 (2002) to 3.09 billion m3 (2017), which was mainly embedded in agricultural and industrial products. This study also reveals the equal importance of physical water and virtual water in ensuring the regional water security and sustainable economic development. In view of poor water resource endowment, Beijing should conduct the coupled management of physical water and virtual water to alleviate the local water shortage, i.e., to receive more virtual water embedded in agricultural and industrial products, and allocate the limited local water resources to domestic use and high-benefit sectors.

Unconventional water resources: Global opportunities and challenges

Water is of central importance for reaching the Sustainable Development Goals (SDGs) of the United Nations. With predictions of dire global water scarcity, attention is turning to resources that are considered to be unconventional, and hence called Unconventional Water Resources (UWRs). These are considered as supplementary water resources that need specialized processes to be used as water supply. The literature encompasses a vast number of studies on various UWRs and their usefulness in certain environmental and/or socio-economic contexts. However, a recent, all-encompassing article that brings the collective knowledge on UWRs together is missing. Considering the increasing importance of UWRs in the global push for water security, the current study intends to offer a nuanced understanding of the existing research on UWRs by summarizing the key concepts in the literature. The number of articles published on UWRs have increased significantly over time, particularly in the past ten years. And while most publications were authored from researchers based in the USA or China, other countries such as India, Iran, Australia, and Spain have also featured prominently. Here, twelve general types of UWRs were used to assess their global distribution, showing that climatic conditions are the main driver for the application of certain UWRs. For example, the use of iceberg water obviously necessitates access to icebergs, which are taken largely from arctic regions. Overall, the literature review demonstrated that, even though UWRs provide promising possibilities for overcoming water scarcity, current knowledge is patchy and points towards UWRs being, for the most part, limited in scope and applicability due to geographic, climatic, economic, and political constraints. Future studies focusing on improved documentation and demonstration of the quantitative and socio-economic potential of various UWRs could help in strengthening the case for some, if not all, UWRs as avenues for the sustainable provision of water.

Ecological network analysis of an urban water metabolic system: Integrated metabolic processes of physical and virtual water

The contradiction between social economy and water environment has become increasingly prominent, and the analysis of urban water metabolism system (UWMS) represents a problem-solving approach from the perspective of the entire flow process. However, a comprehensive UWMS model that considers both physical and virtual water flows is currently lacking. This paper presents an innovative application of an ecological network model of the UWMS-integrated metabolic process of physical and virtual water in Xining during the 2002-2018 period. By analysing and screening the metabolic characteristics, metabolic structure and metabolic relationships, the sustainability of the UWMS is evaluated in depth, and the main causes and critical compartments of the unhealthy metabolic process are identified. The findings show that the UWMS in Xining maintains a moderate level of robustness (the average R = 0.48) with limited metabolic efficiency. Since 2012, the water management policies in Xining have been significantly strengthened, contributing to a slight increase in robustness by improving the water use efficiency and metabolic structure. The integrated metabolic process is unhealthy because the metabolic structure is not reasonable, and the systematic metabolic relationship tends to be antagonistic due to the network mutualism index dropping to 1.0 during 2016-2018. We conclude that efficient irrigation management, more infrastructure projects for the sewer network, wastewater treatment and recycling could provide effective support to enhance the coordinate development of the social economy and water environment in Xining.