Water-energy nexus analysis in an urban water supply system based on a water evaluation and planning model

Consuming less energy and conserving more water are important targets in current water-energy nexus research and practice. However, these targets have not been simultaneously explored in the context of the water supply systems of megacities. In this study, the Water Evaluation and Planning (WEAP) platform is used to explore the energy consumption of the water supply system in Beijing with the energy intensity as the operational cost. The WEAP_Beijing model was built to analyze the energy consumption, water storage, and structure of water supply sources in Beijing from 2001 to 2019. The results indicate that the energy consumption of the water supply system in Beijing has been increasing since 2001; additionally, the energy intensity has increased from 2001 to 2013 and has varied between 1.15 and 1.25 kWh/m3 since 2014. This increasing trend is mainly driven by the increasing ratios of transported water and reclaimed water in the water supply system and by the current use strategy of transported water. Scenario analysis showed that transported water and reclaimed water have increased local water storage but have also led to increased energy consumption, which depends on their ratios in the total water supply and the water use strategy. The water supply structure of each water use sector was simulated and displayed distinct dynamics. An energy-friendly water supply system was proposed to adjust transported water use strategies, optimize the ratio of reclaimed water in the water supply, and manage water and energy from a holistic perspective. The results of this study suggest that a policy evaluation of current water policies is needed to secure and sustain the water supply in megacities.