IWRA Proceedings

Sub-theme

1. Water-Human-Economy(Agriculture, Industry, City...)-Ecology Nexus under a Changing Environment

Topic

1-2. Vulnerability and adaptability of water-land-energy-food nexus

Body

The world is facing significant challenges in securing water, energy, and food due to climate change, population growth, urbanization, and demand increase. Conventional resources management is limited to meet these challenges. A new management perspective, nexus approach ensures the adequate supply of water, energy, and food services while ensuring the sustainability of natural resources simultaneously. Urban Water System (UWS) is an artificial cycle for water use and it includes intake, conveyance, water treatment, transmission & distribution, end-use, wastewater collection, wastewater treatment, reuse, and discharge. A Nexus approach has been widely proposed to support decision-makers in reducing water consumption, energy use, and carbon emissions to identify interlinkages and interdependencies between sectors in UWS. The objective of this research is to derive guidelines, strategies, and action plans for efficient water-energy resource management of UWS. We constructed an energy intensity matrix of UWS, suggested benchmarking tool, and analyzed the water-energy resource usage and efficiency according to external impact and operating efficiency. The energy intensity matrix was constructed with 367 literatures and the data shows the median energy intensity of UWS, water supply system, and sewerage system are 1.210 kWh/m3, 0.519 kWh/m3, and 0.580 kWh/m3, respectively. The most energy intensive process was end-use followed by desalination, reuse, water treatment, wastewater treatment, conveyance, wastewater collection, and discharge. We also suggested the benchmarking tool for evaluating UWS based on the energy intensity matrix. The benchmarking tool classifies UWS into four levels: excellent, good, poor, and bad. It allows stakeholders and decision-makers to identify their UWS in the Nexus perspective. There are two types of driving forces (external impacts and internal impacts) for managing UWS. External impact includes changing water intake source, decreased underground water level, increased imported water, population increase that cannot be controlled by operators. Otherwise, internal impacts such as water loss, lpcd, and hot water use ratio represent the impact that can be managed. We analyzed 54 scenarios with combination of internal and external impacts using a developed system dynamic model. Negative external impacts exacerbate the efficient aspects of UWS, and poor operational efficiency adversely affects quantitatively. Even though numerous researches emphasize the importance of the water-energy Nexus in UWS, there are limited studies with quantitative results. This study allows us to analyze the water-energy efficiency of UWS and trace the UWS changes over time. Therefore, we expect this study to provide guidelines with scientific evidence to decision-makers to formulate strategies and action plans for UWS.