Rain and the city: Pathways to mainstreaming rainwater harvesting in Berlin

Rainwater harvesting has long been part of the standard repertoire of the aspiring sustainable city. The multiple benefits of on-site retention, infiltration and use of rainwater have been illustrated with a plethora of successful pilot projects in industrialized cities across the globe. The leap from niche to mainstream has, however, proved largely elusive. Recent research has provided important explanations for such impeded transitions in terms of unfavourable institutional contexts and obdurate sociotechnical regimes. Little attention has been paid, however, to the urban dimensions of rainwater harvesting. Despite many case studies of rainwater harvesting in cities, we know very little about how the 'urban' shapes, and is shaped by, rainwater management policies and practices. This paper draws on recent contributions to transitions research from human geography and urban studies in order to explicate the dynamic interactions between rainwater harvesting and the city. Taking the city of Berlin - an early pioneer of such technologies - as a case study, it conducts a long-term analysis of the policies and projects implemented to promote rainwater harvesting in the city. The paper's findings demonstrate huge variety regarding not only the instruments applied and schemes developed, but also the political motives and priorities over the past 30 years. This is interpreted spatially and temporally in terms of shifting contexts and contingent events in (and beyond) Berlin. The paper argues for a more nuanced understanding of how the 'urban' permeates sociotechnical transitions in general, and pathways to reconfigure rainwater management in particular.