Impacts of urban water consumption under climate change: An adaptation measure of rainwater harvesting system

Understanding the environmental impacts associated with water-related adaptation measures plays an important role in decision making, as some adaptation measures may not offer environmental benefits compared to traditional water systems. The water depletion index (WDI) is one water stress indicator used to estimate the impacts of water consumption. A dynamic WDI was constructed and employed in this study under climate change scenarios with weather and streamflow modeling. To demonstrate whether adaptation measures can reduce water depletion and to demonstrate how dynamic WDI affects assessment results, Taipei, a highly developed and populated city in Taiwan, was selected as a case study site. Decreased WDI from July to August and increased WDI from September to October were simulated under climate change. This approach implied that when measuring water consumption impacts, the WDI should be applied according to the corresponding time period. Additionally, by substituting 70% of potable water with rainwater in a four-story building, 17.9–159.3 m 3 of the freshwater depletion risk might be reduced every month. As adaptation measures can be long-term strategies and long-lasting infrastructures, a dynamic WDI could provide policy makers with a method to accurately and effectively assess the impacts of applying water-related adaptation measures in response to climate change. © 2019 Elsevier B.V.