Learning processes during regime shifts: Empirical evidence from the diffusion of greywater recycling in Spain

© 2014 Elsevier B.V. All rights reserved. The water supply paradigm in urban Catalonia has experienced a significant transformation toward water decentralization since the approval in 2002 of the first ordinance on water conservation. Local water ordinances make mandatory the installation of rainwater harvesting and greywater reuse systems in new buildings. By 2012, about 50 municipalities in Catalonia had approved similar regulations. This paper analyzes the avenues and limits of the evolution and regionalization of the transition and focuses on the various types of learning that the adoption of greywater reuse systems has triggered in the Barcelona area. During the take-off of the technology, greywater reuse systems were relatively rudimentary but later on, membrane technologies gained popularity which facilitated a more widespread use and acceptance of the technology. The cooperation of the main actors involved in this water transition has been instrumental to move the transition forward but more efforts at the regional level are still required.