Diverse pathways—common phenomena: comparing transitions of urban rainwater harvesting systems in Stockholm, Berlin and Barcelona

© 2019, © 2019 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group. Urban rainwater management is the terrain of varied initiatives that challenge existing drainage systems. The initiatives that this article refers to as Urban Rainwater Harvesting (URH), promise a more sustainable urban water approach; however, they remain isolated “niche” projects. The article aims to investigate challenges and opportunities for mainstreaming alternative URHs as sociotechnical systems (STS). It identifies six analytical categories: context, actors, instruments, processes/dynamics, outputs and impacts as a framework for the analyses of URH projects in Stockholm, Berlin and Barcelona. Despite the diversity of socio-spatial contexts, driving forces, purposes, instruments used, technical designs and scale of URH projects, relevant factors for a breakthrough of these systems are discussed. Even though URHs have not yet become a common component of rainwater management in any of the cities, context-specific combinations of these factors are found to be essential if these systems are to become complementary options for the sustainable management of rainwater in cities.