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

Figures & data

Table 1. The applied criteria (and sub-criteria) for the selection of the nine case studies.

	Selection criteria	Ownership/ Use			Scale		Temporality		Spatiality (Location)		Form		Potential for mainstreaming
City	Project	Public	Commercial	Residential	Large urban development	Small/Individual building	Established	Ongoing	Central	Suburban (periphery)	Neighbourhood (localised)	Linear	Up-scaling	Replication	Transferability
Stockholm	Hammarby Sjöstad	✓		✓	✓		✓		✓		✓				✓
	Årstafältet	✓		✓	✓			✓		✓	✓		✓
	Hornsgatan	✓					✓		✓			✓		✓	✓
Berlin	Berliner Strasse 88	✓			✓		✓			✓	✓				✓
	IKEA Lichtenberg		✓		✓		✓		✓		✓			✓
	Sonnig Wonnig			✓		✓	✓		✓		✓			✓
Barcelona	Jardinet del Pedró	✓				✓	✓		✓		✓			✓
	Can Cortada	✓			✓		✓		✓		✓		✓
	Sant Cugat			✓	✓			✓		✓	✓				✓

Figure 1. Flow chart describing the applied research methodology.

Table 2: Summarising key findings using the theoretical framework

Stockholm	HS	Context	Altered plans according to shifted goals but strong political, financial and legal support, and commitment by the city The city pushed for planning and implementation of URHs
		Actors	The city council and administrations acted as a collective agency A project organisation and a steering team mediating between actors involved and their interests The water utility (SWC) and consultant firms (developers, designers, construction)
		Instruments	Project organisation, envisioning, the Environmental Programme (EP), transition scenarios and measurable operational goals Master, statutory and detailed plans decided through competition
		Processes/dynamics	Strategically led by a skilful and influential project team selected by the city A space for collaborative, deliberative, reflexive and democratic planning processes SWC has an operational role and was less influential in planning and designing processes of URH projects than planners The lack of appropriate maintenance or monitoring schemes compromised social and technical learning
		Outputs	URH projects acted as experiments for building knowledge, though fragmented (which undermined systematic learning) Developed a cross-sector collaboration planning model that was not institutionalised
		Impacts	The planning model is transferred into other global contexts and has become a source of inspiration to many other similar large development projects (e.g. Royal Sea Port, Vasastaden, Hagastaden, Alvsjö)
	ÅF	Context	Legislation for sustainable approaches of treating rainwater Strong financial support and commitment for promoting ambitious URH projects in terms of scale and quality
		Actors	The city administrations, Stockholm Water Company (SWC), consultancy firms (urban design, engineering and architecture), Swedish University of Agriculture Science (SLU) and nurseries
		Instruments	International competition for master planning, envisioning and detailed plans
		Processes/dynamics	Altered plans according to shifted goals A space for collaborative, deliberative, reflexive and democratic planning processes SWC was not involved at the programme level and not directly involved in defining the purposes and designing of URHs Who should maintain what and technical uncertainty (e.g. water flow and efficiency) are still significant challenges
		Outputs	Cross-sector collaboration (water utility and landscape planners) is vital but social learning is not formalised or applied
		Impacts	The project is still undergoing implementation
	HG	Context	The city recognised the need to comply with the EU-regulation for air pollution and pushed the TA to deal with the issue Strong municipal political and financial support and commitment
		Actors	The city council, Traffic and Environmental administrations, SWC for reallocation of underground water pipes only, contractors, constructors, and lately, the Swedish University of Agriculture for the assessment of tree-planting impacts
		Instruments	Tree-planting plan, developed knowledge by the TA, and drawings for the structured soil construction
		Processes/dynamics	Individual agency (from the TA) who developed knowledge and promoted the tree-planting idea and its implementation Strong political advocacy and financial commitment by the city overcame operational challenges
		Outputs	A new tree-bed technique for structured soil using recycled materials and biochar was developed A joint technical learning-by-doing process among planners, civil engineers and constructors
		Impacts	Standardisation and replication of the developed technique; used as a showcase for knowledge transferability Improving urban quality aspects. The TA with the help of SLU is measuring the economic and environmental benefits
Berlin	BS88	Context	Social housing in a well-off borough with no water-related problems Strong political, financial and legal support and commitment initially
		Actors	Initially, the Berlin Senate and borough administration Two public and one private housing association
		Instruments	Funded through federal and Berlin-state programmes and housing companies First time introduction of ecological criteria for funding
		Processes/dynamics	Initiated by the Berlin Senate, top-down Ambiguous distribution of responsibilities led to suboptimal operation Following privatisation of one of the three housing associations residents took over maintenance of parts of the settlement After re-unification of Berlin and its subsequent budget crisis, projects of this scale and type were not replicated and the Senate ended its financial support of the project
		Outputs	No assessment of the effect URH technologies had on water consumption conducted
		Impacts	No particular impacts measured or assessed
	SW	Context	Bottom-up initiative to refurbish an apartment building in Lichtenberg An industrial borough with an ageing population and high unemployment Endorsed by the borough
		Actors	Two initiators – an architect and a planner Borough of Lichtenberg
		Instruments	Some funding received through the “Social Urban Renewal” plan, with the support of the borough
		Processes/dynamics	Grassroots project, with the explicit support of the borough Aims of both main actors coincided, allowing for a collaborative process with active participation and inclusion of residents
		Outputs	Fully functional, in economic, technical and social terms Combination of water reuse and conservation measures led to an 85% reduction in water use Rents have been kept low and affordable
		Impacts	Borough now more open for similar projects; however, rainwater regulations have since become stricter and less conducive to innovative technologies
	IL	Context	Commercial project, initiated by IKEA Sweden and its German subsidiary Located in the industrial boroughs of Lichtenberg and Marzahn-Hellersdorf, part of Berlin’s largest commercial area Public-private partnership
		Actors	IKEA Sweden and its subsidiaries Two boroughs and Berlin Senate (issuing permits)
		Instruments	A split wastewater tariff (with lower payments for run-off from permeable surfaces) was an incentive for retaining water on site
		Processes/dynamics	Internal IKEA process, with little interaction or consultation with the boroughs Well incorporated in the Berlin East Side commercial area
		Outputs	Reduction of both energy and water consumption
		Impacts	Borough officials encourage other developers to follow IKEA’s example, but no measurable impact
Barcelona	JdP	Context	Vertical garden on a dividing wall in a dense neighbourhood lacking green areas
		Actors	Office for the Improvement of the Urban Landscape (Barcelona City Council) Other city council agencies (water, energy, parks and gardens)
		Instruments	Self-funded through commercial advertising
		Processes/dynamics	Initiated by the Barcelona city council, top-down Part of a programme to improve urban landscape after the redevelopment of El Pedró square Integration of URH with renewable energy After some initial problems, well received by owners and neighbours
		Outputs	New green area
		Impacts	Model for replication on other dividing walls in Barcelona
	CC	Context	New social housing project on a hilly terrain in north-eastern Barcelona Rainwater harvesting system to reduce street flooding and sewer overload and replenish aquifers
		Actors	Department of Urban Planning (Barcelona City Council) and especially some planners with interests in these systems Other city council agencies (water, parks and gardens)
		Instruments	Funded by the city council
		Processes/dynamics	Initiated by the Barcelona City Council, top down Initial reluctance by some actors (the water agency did not see Sustainable Urban Drainage Systems - SUDS - as safe enough) Project led by a landscape architect
		Outputs	Gardened public areas to store and facilitate infiltration of rainwater
		Impacts	Reference for the drafting of a blueprint on “Good Practices” for SUDS in Barcelona
	SCdV	Context	Wealthy Barcelona suburb with important outdoor water uses
		Actors	Sant Cugat City Council Contractors and real estate agents Companies installing URH systems
		Instruments	Local ordinance to save water making URH systems mandatory for houses with gardens of a certain size URH systems funded by homeowners
		Processes/dynamics	Initiated by the Sant Cugat City Council, top down Thresholds for garden areas requiring an URH system lowered in successive versions of the ordinance
		Outputs	Reduction in the consumption of water from the public network (not quantified)
		Impacts	Model for other local policies on water retention in the Barcelona area