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Electricity demand in megacities may exert substantial stress on water resources, which is often expressed through the water scarcity footprint for electricity consumption (WSFE). Conversely, water scarcity may constrain electricity production, leading to increased vulnerability for megacities electricity production. The WSFE and the water related vulnerability of electricity production reflect two aspects of water-electricity conflict. This varies over time by both the amount and location of electricity production. However, no studies have conducted time-series analysis to evaluate the trends of these two indicators, both in terms of severity and spatial characteristics. Our study focused on evaluating trends in water-electricity conflict both within and beyond megacity administrative boundaries. China's four provincial-level megacities, i.e. Beijing, Tianjin, Shanghai and Chongqing, were chosen as case studies. The results show that water related vulnerability of electricity production in Tianjin, Beijing, Shanghai and Chongqing was diverse and can be classified as extreme, severe, moderate and minor, respectively. Between 2006 and 2016, the WSFE of Tianjin experienced an increasing trend, and its water related vulnerability of electricity production remained at the highest level. Beijing's WSFE has decreased, but its water related vulnerability of electricity production has increased. These differing trends highlight the need for joint reductions to both WSFE and water related vulnerability of electricity production in mitigating water-electricity conflict., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Abstract In China, vehicle electrification is developed as a way to decouple people's increasing demand for on-road transport and concerns for adverse environmental impacts. Replacing conventional fuel with electricity not only yields impacts on air pollution and greenhouse gas emissions, but also on water resources. This study addresses such impacts for the first time. Based on China's existing plans, we expect China's future electric vehicles will grow from 5 million in 2020 to 80 million in 2030, requiring 47 to 335 TWh of electricity supplies respectively. In order to produce such amount of electricity, under a baseline scenario, 42.60 million m³ and 1.09 billion m³ of water is projected to be consumed and withdrawn in 2020, respectively, which are expected to grow to 324.45 million and 8.56 billion m³ in 2030. Deploying renewable energies offers considerable potentials cutting electric vehicles' indirect impacts on water resources by more than 20% as their productions require less water inputs than coal-fired power plants. Changing cooling technologies' impacts differ by regions, increasing water consumption in southern regions while reducing water consumption in the north. However, if water consumption avoided from avoiding conventional fuel productions is taken into account, compared to the counterfactual scenario where the same number of traditional vehicles will be deployed, future electric vehicles in China will lead to net decreases of 19.3, 64.3 and 89.7 million m³ of scarce water consumption nationally under baseline, high renewable and cooling technology change scenarios in the electric power sector respectively. Highlights • Electric vehicle (EV) amount is expected to reach 80 million in China by 2030. • From 2020 to 2030, electricity demand by China's EVs will increase by 6 times to be 335 TWh. • 8.56 billion m³ of water will be withdrawn by electricity generation for EV in 2030. • EV rising can save water in North China by avoiding oil production. [ABSTRACT FROM AUTHOR]

• Megacity water resource network should include physical and virtual water supply. • Input-output analysis is used to analyze megacity water vulnerability. • Megacities were more vulnerable to external than internal water scarcity. • Virtual water inflow help decrease vulnerability in water stressed megacities. The water resource networks that provide water for urban consumption consists not only of physical water supply, but also water embodied in imported goods and services i.e. virtual water supply or external water footprint. However, it remains unknown that if relying on external water footprint will increase or decrease the vulnerability of cities' water resource networks. Here, we evaluate the vulnerability of urban water resource networks for China's six megacities i.e. Beijing, Tianjin, Shanghai, Chongqing, Guangzhou, and Shenzhen. The vulnerability index was developed through combining a refined multi-region input-output table with both water footprint and water scarcity footprint analysis. The results showed that megacities need to import large volumes of virtual water embodied in food related sectors to balance their physical water shortages. The external blue water footprint (BWF) of the six megacities accounted for 80.7% of their total BWF, and was almost twice their physical water supply. The large share of external BWF helped Beijing, Tianjin, and Shanghai, which suffer extreme water stress in their urban areas, to decrease their total vulnerability by 39%, 33%, and 28% respectively, but conversely increase their vulnerability to external water shortages i.e. indirect vulnerability. Establishing megacity physical and virtual water resource networks based on input-output analysis provides an opportunity for urban water planners to internalize the risk of their external water footprint. Avoiding import water-intensive products from regions suffering extreme water stress, or managing indirect vulnerability through cooperation with those regions are suggested as viable water management approaches. [ABSTRACT FROM AUTHOR]

• The water scarcity footprint enables meaningful spatial comparisons of water impact. • We compared the water scarcity footprint of energy demand for 6 Chinese megacities. • Our results highlight the impacts of energy demand extend beyond the city boundary. • The water scarcity footprint of northern Chinese megacities is higher than southern. • Fossil fuel processing in northern China contributes to scarce water consumption. Water is required throughout the life-cycle processes of energy production to meet the growing energy demands in China's megacities. However, the spatially explicit impact on water scarcity both inside and outside the megacity boundaries from megacities' energy demands remains unknown. We quantified and compared the water footprint and water scarcity footprint for final energy demand (WFE and WSFE) in China's megacities from a consumption perspective. Six acknowledged megacities, i.e. Beijing, Tianjin, Shanghai, Chongqing, Shenzhen and Guangzhou, were evaluated with an extended multi-region input–output model. The results showed that these megacities were endowed with only 2.60% of the national available water resources, but their WFE (WSFE) made up nearly 14.00% (13.50%) of the national total. The megacities located in Northern China generated a larger WSFE in their WFE than the cities in Southern China. Energy demands in these megacities were heavily dependent on scarce water sourced from beyond their administrative boundaries, together importing 84.10% of WSFE from elsewhere. Electricity demand dominated the volumetric water consumption, representing 52.00% of the WFE. The distribution was different for scarce water consumption, with coal demand generating 34.00% of total WSFE, followed by electricity (31.00%) and petroleum (26.00%). Although Northern China is faced with dire water scarcity, its scarce water is still being predominantly outsourced to support energy demands in both Northern and Southern megacities, mainly due to their coal and petroleum reserves. Location-specific pathways and foci should be applied for different megacities to decouple their energy demands and their scarce water consumption. [ABSTRACT FROM AUTHOR]

Several studies have demonstrated the continuum of cooperation on transboundary rivers, but have largely focused on government to government (Track 1) cooperation and formal diplomacy. Formal arrangements like treaties, agreements, joint mechanisms, joint bodies, joint commissions (e.g., river basin organizations), etc., fall within the scope of transboundary waters cooperation. However, in some transboundary rivers, often due to political constraints, Track 1 cooperation might not be a feasible option. When governmental cooperation is a non-starter, effort and progress made outside the government domain through informal dialogues can play a significant role. It is therefore important to re-examine the definition of cooperation as it applies to international rivers, and potentially to broaden its scope. Such an examination raises important questions: What does international cooperation in this context actually mean? Is it formal (Track 1) cooperation related to sharing of water, data, and information only, or does it have a broader meaning? What, precisely, can be the entry point for such cooperation? Are informal transboundary dialogues and water diplomacy itself an entry point for cooperation on international rivers? This paper aimed to answer these critical questions drawing from the "Brahmaputra Dialogue" project initiated in 2013 under the South Asia Water Initiative (SAWI), which involved the four riparian countries of the Brahmaputra Basin. Several important focal points of cooperation emerged through this sustained dialogue, which went beyond sharing hydrological data or signing a basin-level treaty, broadening the definition of "cooperation". The paper, bringing evidence from the dialogue, argues that the Brahmaputra Dialogue process has led to a broader understanding of cooperation among basin stakeholders, which could influence water resource management of the basin in the future. [ABSTRACT FROM AUTHOR]