Integrating private water systems into the holistic management of the urban water cycle

ABSTRACT The figure presents presents the evolution urban water cycle management from the traditional to the holistic approach, in which the spaces in the city become also sources of water and sinks for wastewater and stormwater. This evolution enhances the circularity of urban water cycle, reducing the environmental pressure both for water consumption and wastewater discharge, while reducing urban flood risk. At an urban level, water supply and wastewater drainage are usually managed considering a separation of the public (off the buildings) and private system (on the buildings) roles. However, for a more sustainable urban water cycle management capable of facing future water-related challenges, this separation of roles is not effective and a holistic approach is required. The present contribution reviews the evolution of the urban water cycle management approaches and discusses the potential of implementing solutions in private systems to increase water efficiency, satisfy water demand needs and contribute to wastewater and stormwater discharge reduction at an urban level. The goal is to connect the research on the topic of sustainable urban water cycle, which has focused more in the public infrastructures (e.g., water losses reduction) and decentralized systems (e.g., retention ponds), and include the solutions available to implement in the buildings, namely, water-efficient appliances and fixtures, greywater use and rainwater harvesting, along with nature-based solutions such as green roofs and managed aquifer recharge.