How can we adapt together? Exploring barriers, drivers, and tools for collaboration between water and urban experts Open Access

The increasing frequency of climate change-related events such as droughts and floods is challenging the conventional paradigm of city governance and exerting growing pressure on established urban planning and management practices (Koop et al., 2022; Roque et al., 2023). Understanding how cities can adapt to these concurrent challenges, such as population growth, escalating urbanisation, and climate change, is essential. This adaptation journey encompasses various facets of city action and governance structures, involving entities with diverse responsibilities and often conflicting interests. However, it also presents opportunities for shared needs that can catalyse collaborative projects and water city government approaches (Hurlimann & Wilson, 2018; Göransson et al., 2023; Pék et al., 2024). Numerous examples abound, showcasing efforts to tailor cities to the challenges posed by climate change. However, most practical instances predominantly address adaptation to extreme phenomena linked to the ‘excess of water’ (Hurlimann & Wilson, 2018). Conversely, limited attention has been given to how cities adapt to emerging issues associated with the ‘lack of water’. This scarcity stems from various factors such as insufficient water availability at sources (either on an average or occasional basis), wasteful water practices, or the absence of adequate demand control, among other significant contributors (Hurlimann & Wilson, 2018; Rich et al., 2023). Notably, there is a noticeable dearth of studies exploring how collaboration with city planning, whether on a micro or macro scale, can play a role in mitigating these challenges, which are further exacerbated by the impacts of climate change (Bryson et al., 2015; Malekpour et al., 2020).

The challenges arising from climate change have also led to the emergence of various concepts related to urban adaptation. Noteworthy contributions from authors such as Fletcher et al. (2015) and Miranda et al. (2022) have been instrumental in understanding these concepts, as they define and catalogue the main concepts of water circularity and the adaptation of cities to climate change in the water sector. Considering the evolving water management challenges in urban areas, Marlow et al. (2013, p. 2) propose the overarching concept of sustainable urban water management (SUWM). They define that ‘as an aspiration, SUWM reflects a generalised goal to manage the urban water cycle to produce more benefits than traditional approaches have delivered’. Barron et al. (2017), also define that ‘SUWM is advocated by an increasing number of scholars as an alternative paradigm to traditional water infrastructure and approaches, which can address the complex challenges facing urban water management. SUWM is an umbrella concept that encapsulates the concepts of ‘integrated urban water management’ and ‘water-sensitive urban design’. Implementing SUWM measures includes soil permeabilisation, strategic flora distribution, urbanisation density, spatial planning considerations (including the location and type of activities), the proximity of constructions to watercourses, the establishment of ‘recycled water factories,’ drainage system types, and the delineation of ‘blue’ and ‘green’ zones. These measures embody actions that intricately connect spatial planning with urban water cycle management (Domene & Saurí, 2006; Ferguson et al., 2013a; Gober et al., 2013; Chan et al., 2018).

These types of measures emphasise the interconnectedness of urban water cycle management and spatial planning within the governance of cities. The symbiotic and collaborative development of these aspects is crucial for adapting cities to climate change and the challenges posed by increasing urbanisation. The trajectory cities embrace to strengthen collaborative steps within adaptation could serve as a guiding model for how urban areas can broaden their understanding and initiatives to cope with extreme weather events, including those associated with the ‘lack of water’. This paper delves into the perspectives of officials in cities that have already started this adaptation path, along with insights from key experts of international organisations such as the IWA, Water Europe, Energy and Climate Forum, and Lis-Water. The objective is to explore their perspectives on barriers, drivers, and tools for enhancing collaboration between water utilities and spatial planning authorities. In doing so, it enriches the existing body of knowledge, as established by scientific research and grey literature. In this article, a barrier to collaboration refers to any factor or obstacle that hinders an organisation or system from adjusting to new conditions, circumstances, or environmental changes. A driver for collaboration is a factor or force that encourages and facilitates adjusting to new conditions, circumstances, or changes in the environment (Kabisch et al., 2016). The drivers play a crucial role in promoting adaptability at the organisational level; understanding and leveraging these drivers can help organisations thrive in dynamic and ever-changing situations related to climate change (Ansell & Gash, 2008). Tools for collaboration, refer to resources, strategies, or instruments organizations can utilise to facilitate and implement desired changes. Specifically, these tools are instrumental in facilitating the adaptation of city planning, with a focus on the urban water sector, in the context of a changing climate (Malekpour et al., 2020). Drivers may incentivize the use of tools, and the barriers influence the success of the implementation of tools. Given the complexity of challenges cities currently face, a comprehensive understanding of these barriers, drivers, and tools is essential for designing any adaptation strategy.

This article addresses the following research questions: (i) how collaboration between water utilities and spatial planning authorities under a climate change context is being considered in the management of the urban water cycle and city planning; (ii) which barriers, tools, and driving forces for collaboration are influencing the success of the city's adaptation in this context? This study brings to the fore replies to these questions by analysing the contributions of senior officials associated with water utilities and urban planning agencies from cities that have made significant progress in adapting to climate change. Moreover, it collects insights from senior officers and leaders of international organisations committed to this adaptation, offering a thorough overview of collaboration between water utilities and spatial planning authorities. The study focuses on identifying key barriers, drivers, and tools for fostering effective collaboration in urban areas. This offers a novel contribution to scientific understanding about collaboration for climate change adaptation in cities and clues to improve water management in cities.

The article is divided into six sections. Following this introduction, Section 2 presents a brief state of the art. Section 3 describes the methodology used to identify the interviewees and design, implement, and analyse the interviews. Section 4 presents the results obtained from the interviews, and Section 5 presents the discussion. Section 6 outlines the main conclusions.

In managing freshwater resources, cities play a significant role, as they can influence both water quantity and quality through land-use changes, overexploitation, and contamination (Li & Marina Bergen, 2017). Wong & Brown (2009) emphasised that achieving SUWM requires cities to prioritise water as a central component of urban development. They advocated for a holistic approach that integrates urban design with disciplines responsible for water provision. This integrated method recognises the interconnectedness of key design elements, which significantly influence the ecological footprint of urban areas. These impacts extend to critical aspects such as energy consumption, carbon emissions, water conservation, environmental protection, and biodiversity. Additionally, cities must develop social-political capital to effectively engage with water issues. Future urban landscapes must also embrace opportunities and technologies to enhance cities' resilience against the impacts of climate change, which have already introduced uncertainties regarding urban water supplies and extreme weather events (Li & Marina Bergen, 2017). Addressing these challenges necessitates cross-sector collaboration; as such partnerships are vital for tackling complex public issues like these (Bryson et al., 2006). This cross-sector collaboration, or in the context of this paper, the collaboration between urban and water sectors, involves sharing information, activities, capacities, resources, and decision-making among organisations and actors in two (or more) sectors. The aim is to achieve outcomes that are not attainable separately (Bryson et al., 2015; Malekpour et al., 2020).

The complexity of the interdependencies guiding the adaptation of the urban water cycle to climate change is multidimensional (Vinagre et al., 2023). However, the interrelationship between these dimensions remains unclear, particularly the role of institutional collaboration and the barriers, drivers, and tools that shape it. These factors influence, enable, and structure how a typical city addresses the challenges posed by climate change. The scientific literature already mentions a range of barriers, drivers, and tools for collaboration that deserve consideration. Regarding the barriers, the main items that appear in the literature include the perception that traditional centralised systems are more reliable and require less collaboration (Koop & van Leeuwen, 2017), a history of limited institutional collaboration (Gober et al., 2013), inadequate legislation for water reuse, which discourages cooperative efforts (Tompkins et al., 2010), governance uncertainties in decentralised systems requiring greater inter-institutional involvement (Moglia & Cook, 2019) and a lack of knowledge, time, trust, or perceived benefits of collaboration (O'Donnell, 2012; Ferguson et al., 2013b). Concerning the drivers that foster collaboration, the literature presents the need to resize cities according to the variation of their population and urbanisation (Marlow et al., 2013), the climate change perception (Craddock et al., 2021), the increased consumption of water (Larsen, 2015), the public perception of the waste of drinking water (Gober et al., 2010), the public sensitivity to self-sufficiency and circularity of the economy (Miranda et al., 2022) and pre-existing collaborations and effective conflict management strategies (Klijn et al., 2010).

Respecting the tools that emerge from the literature we find the progressive hybridisation of centralized and decentralised systems and the use of alternative sources of water systems that enforce the need for collaboration (Sapkota et al., 2015), the land use policy influencing demand and offer (Hurlimann & Wilson, 2018), the levels of collaboration and related levels of impact (Malekpour et al., 2020) the effective trust building (Edelenbos & van Meerkerk, 2015), the distributed leadership (Barrutia & Echebarria, 2019), the correct accountability of collaborative efforts (Rygaard et al., 2011; Frantzeskaki et al., 2014) and the pursuit of small wins in collaborative endeavors (Ansell & Gash, 2008).

Considering the conceptual context introduced in the previous paragraphs regarding the barriers, drivers, and tools for collaboration for adaptation, based on the literature, it is worthwhile to further explore the topic by studying how experts working on cities where progress for the transition to adaptation and recognised water and climate-related international organisations are perceiving the relevance of those concepts and which are most outlined for the success of collaboration.

Given the study's objectives, particularly the analysis of officials' perspectives on collaboration for adaptation, a set of interviews with water professionals was undertaken, focusing on three core aspects closely aligned with the research questions: gathering insights into various cities' efforts to adapt to climate change; delving into the primary barriers, drivers, and tools for collaboration for adaptation identified by interviewees and their critical perspectives on the success of the transition to adaptation. To this end, an interview protocol for the semi-structured interviews was designed to include four foundational questions: How have cities been adapting to climate change in the water sector? What is the role of collaboration between institutions in this adaptation? What are the main barriers, drivers, and tools for collaboration for adaptation? What role do national policies, legislation, and regulations play in this context?

The questions asked to city experts sought the identification of barriers (types and sources), drivers (for example, generic motivators and incentives, presence of joint task forces, involvement of the water service providers (WSPs) in city planning instruments), and tools (for example, collaborative measures outlined in the planning processes, citizen involvement, ‘array of ‘quick-fix’’ technical solutions). In the case of officials linked to other organisations, where a specific city context was not applicable, the questions were more open-ended and reflective but still aligned with the same three key aspects – barriers (which and by whom), drivers (financial considerations to foster collaboration; the role of national policies and legislation) and tools (collaboration mechanisms; taxation; known best practices). The topic of collaboration and its significance in cities' adaptation to climate change was consistently introduced to better explore how the interviewees perceive its importance and which types of barriers, drivers and tools they consider relevant.

The selection of interviewees from cities considered cities actively involved in on-site initiatives, ensuring firsthand experience with the challenges and opportunities inherent in their urban water management efforts. This approach aimed to provide a comprehensive understanding of the complexities involved, thereby contributing to a well-founded basis for this study. The study took into account the insights gleaned from the IWA's Water Wise Cities initiative (International Water Association, 2016), where strategic measures have been devised to enhance urban water resilience, and the cities actively involved in the UNaLab project (UNaLab Consortium, 2017), which has significantly enriched the European knowledge base on nature-based solutions (NBS). This emphasis on NBS served as an exemplary model, demonstrating how the integration of the urban water cycle with city planning can be effectively articulated to design resilient urban environments. It also highlighted opportunities for collaboration between water utilities and urban planning. The primary objective of the interviews with city officials was to uncover how these cities valued the collaboration between water utilities and spatial planning for water-related adaptation, along with the associated barriers, drivers, and tools, in their pursuit of enhancing urban resilience. Additionally, the selected cities were chosen to offer diverse climatic perspectives, addressing challenges that were complementary in some respects. The cities of Berlin, Brisbane, and Amsterdam (from the IWA Water Wise Cities initiative), as well as two cities from the UnaLab project, Tampere and Eindhoven, were subjected to in-depth analysis. The city of Lisbon was also included due to the accessibility of the authors and recognising the advancements made in recent years in the city's adaptation to climate change in the water and urban planning sectors. Table 1 presents the key characteristics of the cities under study.

Purposive sampling was employed to identify and select the interviewees. The purposive sampling aimed to target respondents with significant core experience from diverse perspectives, ensuring informed and insightful responses during the interviews. This method involves choosing participants across a broad spectrum relevant to the study's topic, encompassing various perspectives to achieve a comprehensive understanding (Etikan, 2016). Purposive sampling is deemed suitable for qualitative analyses, mainly when it hinges on the expertise of individuals who meet specific criteria such as years of experience or holding key positions in entities contributing to the study's theme (Etikan, 2016). The interviewees included senior officers and directors in the six selected cities with the following distribution: Berlin (2), Amsterdam (2), Brisbane (1), Eindhoven (1), Lisbon (3) and Tampere (2). These individuals represented various sectors, including spatial planning, urban water, and departments specifically established for an integrated response to climate change within the cities (water-related).

In addition, interviews were also undertaken with key officials possessing recognised expertise in water management in the urban context with responsibilities in the International Water Association (Strategic Programs and Engagement), Water Europe, LIS Water, and Energy and Climate Forum.

Overall, the chosen interviewees, with an average of 24 years of experience in the urban water or planning sectors, underscore the wealth of knowledge and perspective provided by highly experienced experts for qualitative analysis. The 15 qualified semi-structured interviews undertaken, while of a small number, align with similar studies in the literature (e.g., n = 10, (Portman et al., 2022); n = 10, (Hacker et al., 2020); n = 12, (Mastroianni et al., 2021)). Table 2 presents the list of interviewees and their backgrounds.

The interviews were conducted between July and December 2023 via online video calls in English and Portuguese. Each call lasted, on average, approximately an hour and a half.

A three-step methodology was applied to analyse the interview responses. First, each author independently reviewed the responses to identify the barriers, drivers, and tools mentioned, ensuring an unbiased analysis. Second, the independent analyses were then discussed among the authors and merged into a comprehensive synthesis. Third, the responses were systematically categorised into the sets of barriers, drivers, and tools for collaboration referred to by the interviewees, as presented in Table 3 of the next section, where the findings of the empirical study are presented.

The broad results of the interviews are summarised in Table 3. The table shows the types of barriers, drivers, and tools referred to by the interviews according to their origin city and organisation. It is visible that the officials from the cities of Amsterdam and Eindhoven refer to richer sets of types of barriers, drivers and tools, followed by the officials of Berlin and Tampere. The analysis of these results is presented in the following paragraphs.

One of the barriers identified refers to the absence of national strategies and regulations that provide a visionary outlook, outline objectives, establish accountability mechanisms, and regulate and support the transition. This absence hampers the paradigm shift, particularly in cities where the local level of governance may not be inherently motivated to tackle this issue, even if mandated. Developing these strategies is considered pivotal in fostering a cohesive and harmonised approach to climate adaptation, encouraging local governance to embrace and implement effective measures. The presence of multiple layers of governance, not always aligned collaboratively, is considered to pose an additional barrier to formulating integrated strategies for city adaptation.

Another primary barrier referred to by experts as hindering the implementation of adaptive measures in urban areas relates to the insufficient emphasis and safeguarding of the ‘water’ theme in city design. Essentially, WSPs' approaches still predominantly address the urban water cycle through a linear lens, primarily focusing on ‘water supply’ and ‘water drainage’. Although responsibilities may differ across the cities examined, water treatment in spatial planning remains suboptimal, positioning water as an ancillary element rather than a central consideration in urban design, especially in the face of imminent challenges. None of the interviewees indicate a central role in climate change adaptation during the periodic reviews of spatial planning instruments for their cities. This implies that measures concerning the interplay between city planning and the urban water cycle soon will likely be incremental and opportunistic rather than systematically integrated. The current lack of centrality regarding the adaptation of cities to climate change in spatial planning instruments highlights a crucial gap that needs urgent attention to address challenges proactively. Therefore, there is a need for the topic of water to be integrated into territorial management instruments, which can only be achieved through collaboration among the diverse institutions responsible for water and land management. For instance, Lisbon's experts consider that the challenge arises from the placement of Wastewater Treatment Plants (WWTPs) in specific city areas and significant water consumers in other locations, such as urban parks, street cleaning, golf courses, or large industrial zones. Due to high capital expenditure (CAPEX) values, this frequently results in the impracticality of transporting reused water across the entire city. Therefore, they consider a need to strategically plan and foster physical proximity between water producers and consumers.

One barrier hampering cities' transition to climate change adaptation, which encompasses both stormwater management and addressing water scarcity, is the initial challenge of inadequate space within urban centers for implementing adaptation measures. This barrier, notably evident in cases such as Tampere or Eindhoven, posed obstacles to implementing nature-based solutions or biofilters in those cities. Additionally, a noteworthy concern is the ad hoc nature of some adaptation investments, which hinders a comprehensive understanding of how city-wide interventions can foster the necessary resilience and how to measure it effectively.

Another type of barrier to collaboration, as indicated by the interviewees, arises from a prevailing tendency towards conservatism. In some instances, it was noted that the managing entities show signs of aging and often lack the necessary training to facilitate a seamless transition towards climate adaptation. This challenge is exacerbated as the scale of the municipality decreases, given that these issues involve non-immediate returns and demand resources that many cities may lack. Even in larger cities with diverse functions, the prevalence of a ‘business as usual’ mindset, coupled with a ‘dearth of training’ in these critical subjects and ‘structural rigidity’, further obstructs dynamic progress in the adaptation of cities. A concerted effort to address spatial limitations, enhance training programmes, and foster flexibility within administrative structures is essential to promoting effective climate change adaptation.

According to the interviews, several factors are deemed pivotal in determining the success of cities in adapting to climate change. The analysis of the responses reveals that the impetus for effective adaptation and collaboration between institutions often originates from the political sphere using a typical top-down approach. This is primarily influenced by growing citizen awareness, which naturally has electoral repercussions. However, a prevailing notion suggests that while flood control measures, integral to adaptation, can and should be managed at the local governance level, measures about water reuse, often of a more technological nature and requiring robust financial viability, are better suited for centralised and enduring management through dedicated entities.

Another type of driver mentioned by the interviewees relates to the preference for an aggregated governance level that facilitates the articulation of significant adaptation measures on a larger scale, over a longer term, and with increased funding. Collaboration between SPAs and WSPs is considered not just a possibility but an essential alliance for city adaptation to climate change. However, from the analysis of the responses, it is concluded that existing collaborations tend to be more consultative than immersive, often confined to specific projects.

From the interviews, it emerges that at the city level, notable examples such as Amsterdam, Berlin, Eindhoven, and Tampere showcase the effectiveness of specialised multidisciplinary structures acting as ‘change facilitators’ propelled by collaboration. These structures and a well-organized communication process adeptly convey the concept of urban adaptation to climate change. They offer guidance and support and require technical input from public and private stakeholders. The presence of water reform blueprints, exemplified by Australia's National Water Initiative (Australian Government, 2004) and its ongoing renewal process (Water Services Association of Australia, 2023), played a crucial role in Brisbane. The interviewees considered that such initiatives allowed for the definition of objectives, targets, and opportunities for a comprehensive water sector transformation, particularly in the context of climate change, fostering unity among various levels of governance.

From the insights gathered from interviews with city experts, it is evident that the coordination between water utilities and city planning, when present, has revolved mainly around incrementally adapting the existing urban landscape and infrastructure to meet the demands of climate change on specific projects. None of the experts from the cities referred to the existence of a comprehensive rationale for redesigning urban spaces or a holistic adaptation to climate change, whether for protection against extreme events or the redefinition of spaces and networks to optimise water reuse. One key factor cited for this absence is the urban consolidation of cities, where the required investments and potential disruptions are perceived as herculean and financially unattainable, even in developed countries.

The predominant focus has been on incremental and, in some cases, opportunistic measures, as the overarching and integrated adaptation of cities has not yet assumed a central role in city planning. For instance, the expert from Eindhoven reported that incremental adjustments to their road networks have been made to ‘enhance resilience against extreme flood-related events’. The experts from Amsterdam outlined 14 concrete implementation collaborative design measures promoted under the Amsterdam Rainproof program (Amsterdam Rainproof, 2014), aimed at ‘increasing the city's and private owners’ resilience to extreme events’. The program adopts a ‘brownfield’ intervention perspective, actively involving citizens in some cases, with investment and participation from private owners.

Similarly, experts from Tampere refer to a logic of specific interventions, developing numerous biofilters and constructing wetlands in a public investment framework. Additionally, they refer to the fact that private investors have contributed to the construction of green roofs and walls, driven by the city's ‘Green factor’ initiative, wherein the city sets targets for the ratio of green area to lot area in detailed city plans. These examples, although valid, illustrate a trend towards localised and targeted initiatives rather than a comprehensive reimagining of city structures in the face of climate change. In this line of thought, except for particular situations, experts from the city of Berlin, grappling with the incapacity of its drainage infrastructure to cope with more frequent extreme events, suggest a trend towards prohibiting the discharge of water generated on individual lots into public rainwater collectors, provided there is sufficient soil space for infiltration. In instances where a connection is permitted, an annual contribution is levied based on the waterproofed area of each urban property, determining the corresponding fee. For unitary networks, the construction of new connections is strictly forbidden.

Regarding flood control approaches, interviews reveal that cities primarily implement measures such as the obligation to retain water on each property, as seen in Amsterdam, Berlin, and Tampere. Collective solutions are also embraced, mainly through the construction of water retention and infiltration infrastructures in public spaces. In certain cities studied, such as Amsterdam, Eindhoven, Berlin, and Tampere, experts note the existence of a stormwater-related tax. Notably, in cities like Tampere, the revenue generated from this tax is directed toward the construction of adaptation measures like NBS, which sets them apart positively in terms of the speed of implementation compared to other cities lacking such funding mechanisms.

Interviews with non-city experts revealed that national regulations defining fundamental parameters and adaptation objectives are crucial for the widespread adaptation of cities and the effective implementation of measures. Similarly, detailed municipal regulations outlining specific goals and objectives for the entire city and at the level of individual land parcels or new construction projects act as a catalyst for this transformative change.

The following section discusses these results considering the literature.

The results of the interviews, given the predominantly empirical nature of the interviewees, enriched scientific knowledge by providing a new perspective on the barriers, drivers, and tools already discussed in the scientific literature, which tend to be presented more theoretically. Indeed, although the need for cross-sector collaboration is already highlighted in the literature, some barriers, drivers, and tools for its implementation have not been identified. Examples of newly identified barriers include the difficulty of interventions in well-established urban areas, the lack of a national strategy, many layers of governance, and the lack of technical knowledge and financial capacity. Among the drivers, we emphasise the importance of political kick-offs and political support, the presence of change facilitator teams, and national strategies that motivate and enforce change in cities, along with municipal regulations that compel collaboration between entities. Finally, newly identified tools include the rapid availability of technical solutions for implementation by citizens and entities, deeper collaboration between producers and consumers of reused water, collaborative design, and aspects related to implementing measures in private sectors through appropriate taxation and pricing.

Considering the research questions and the results obtained, the subsequent paragraphs will delve into an analysis of how climate change adaptation is being considered in managing the urban water cycle and city planning and which factors are influencing the success of this transition. They will also focus on drawing lessons for enhancing collaboration between city planning and the urban water cycle within the climate change framework and escalating urbanisation, especially those related to water scarcity. As each city has its context, emphasis will be placed on examining structural measures that have played a pivotal role in instigating a paradigm shift in the studied cities. Additionally, attention will be given to exploring how these structural measures can be effectively disseminated and adapted to different contexts.

As expected, the maturity of managing entities plays a crucial role in determining a city's readiness to adapt to climate change, particularly in the context of becoming water-sensitive (Wong & Brown, 2009). The stage of transformational progress within a city becomes a pivotal factor influencing its disposition towards climate adaptation challenges (Ferguson et al., 2013b). Cities grappling with fundamental issues in water supply and sewage management tend to prioritise resolving these immediate concerns over preparing for the inevitable impacts of climate change, despite their increasing visibility.

In less developed countries, where necessities like water supply and wastewater sanitation remain unresolved due to their embryonic stage of development, the incorporation of SUWM measures is often sidelined (Li et al., 2015). The managing entities in these regions focus on addressing fundamental needs, with climate change concerns taking a backseat. Nevertheless, this underdeveloped stage presents a unique opportunity to establish robust foundations for future development. By approaching the situation with awareness, a well-defined strategy, and adequate financial support, these countries can avoid the more opportunistic and reactive paths followed by more developed nations. In essence, they can ‘build well from the beginning’ and create sustainable solutions, provided the necessary resources and commitment are in place.

Beyond those studied in this article, numerous cities have implemented various measures to adapt to climate change (van Leeuwen et al., 2012; Voskamp & Van de Ven 2015; Puchol-Salort et al., 2021). These efforts encompass a range of structural interventions to prepare them for this challenge. Notable measures, particularly in city planning, building and management, include the implementation of blue or green infrastructures, water reuse, water reuse building networks, xeriscaping (the process of landscaping or gardening that reduces or eliminates the necessity for irrigation), green roofs, restrictions on lawn implementation, and the use of pervious pavements, among others (Vinagre et al., 2023). Despite these efforts, there remains a notable absence of contributions from the WSPs in city planning and building guidelines, particularly concerning collaboration with the urban water cycle.

Considering the opinions of the officials, an increasing integration of perspectives between SPAs and WSPs is essential for a proper water transition in cities. Still, collaboration between these different ‘silos of responsibility’ remains sporadic. In most cases, it is project-based and not viewed from a joint genesis. The challenge of integration persists in viewing ‘water’ in a broad sense as a ‘transversal’ theme rather than a ‘vertical’ one, deserving independent importance. Despite initiatives such as the EU Blue Deal emphasising water as a strategic priority (European Economic & Social Committee, 2023), the overarching perception remains that water lacks a central role.

A robust sectoral regulatory body and the establishment of a national strategy for the water sector, including its adaptation – as in Australia (Australian Government, 2004) – proved to be instrumental, not only in acknowledging the intrinsic value of water but also in defining shared objectives, productivity benchmarks, and efficiency targets. These strategic frameworks provide a sense of security for entities involved in the transformational process, fostering a more ambitious and innovative vision within the context of climate change. Additionally, it facilitates regional comparability and enables informed decisions on optimal investment choices.

At the local level, the existence of departments dedicated to facilitating ongoing collaboration, even with limited staffing, also represented a crucial step towards aligning city planning and the urban water cycle. These dedicated efforts, coupled with investments in joint measures for climate change adaptation, contributed significantly to the focus on the interconnection between these two vital areas. Moreover, the infrastructural and operational maturity of WSPs and SPAs, coupled with secured financial funding, further enhanced the proactive stance of cities in addressing the challenges posed by climate change, even when such challenges may not be immediately apparent. This comprehensive approach, encompassing strategic planning, collaborative efforts, and financial stability, positions cities to effectively confront and adapt to the impacts of climate change in the water sector.

Since adaptation efforts in cities regarding ‘lack of water’ are less developed compared to those addressing ‘excess of water’ (Li & Marina Bergen, 2017; Hurlimann & Wilson, 2018), there is an imperative need to enhance the urban design process, considering the availability of water, whether freshwater or reused, as a potent factor influencing the expansion of cities, both in location and typology of use. Addressing water reuse measures presents challenges, especially in adapting city centers and buildings to incorporate new infrastructures like recycled water treatment, distribution facilities or internal networks. The spatial mismatch between treatment facilities, often situated outside city centers, and recycled water consumers create long distances between recycled water production and consumption points, posing a threat to the economic viability of projects. In large-scale city expansions, whether in greenfield or brownfield developments, strategic consideration of the location of these ‘recycled water factories’ and their correlation with potential consumers becomes crucial, mainly when water scarcity is a prevalent concern. Defining a clear hinterland of influence for each central recycled water production facility could be a strategic planning instrument.

In consolidated city centers, adaptation to climate change proves challenging due to historical constraints, limited space, or interference with private property. Regulatory mechanisms recommending or mandating technical adaptation measures, as exemplified by cases in Tampere and Berlin, are essential. While specific measures can be left to developers' discretion, predefined targets must be met. Establishing standard technical measures facilitates a smoother transition and accelerates the learning curve, as demonstrated by initiatives like Amsterdam Rainproof (Amsterdam Rainproof, 2014). Collaboration with diverse stakeholders, particularly universities combining scientific knowledge with regional and national information, proves instrumental in supporting the transition to climate change adaptation, as referred to by Malekpour et al. (2020). Communication and citizen engagement are also vital components, acknowledging that adaptation must be comprehensive, involving all facets of a city. Recognising the enormity of the adaptation challenge, appropriate financing becomes crucial, whether through central state budgets or citizen contributions, striking a balance that ensures the sustainability and effectiveness of city adaptation initiatives.

This study acknowledges certain limitations that arise from the use of purposive sampling, the sample size, the age of the interviewees, the focus on stormwater, the context of each city and the selection of geographies often markedly distinct from each other. While this deliberate diversity enhances the richness of the study, it also introduces a potential challenge of incoherence in responses to contextual questions. Despite these limitations, the study is original and significantly contributes to the existing literature. The multifaceted exploration of case studies of cities' adaptation to climate change is a distinctive aspect of this research. Nonetheless, we endeavored to gather insights from impartial entities and experienced individuals with a global perspective. This approach enables a broader scope for the study, considering the context of less developed regions. Given the scarcity of studies that delve comprehensively into this complex subject, the insights provided, even within the acknowledged constraints, contribute valuable perspectives and findings to the broader body of knowledge. The study thus represents a noteworthy effort to address the current gap in research. It offers a foundation for future investigations into the multifaceted dynamics of urban adaptation to climate change.

This article delved into the perspectives of officials in a set of cities that have already started an adaptation path, along with insights from key experts of international organisations such as the IWA, Water Europe, Energy and Climate Forum and Lis-Water to identify major barriers, drivers, and tools for enhancing collaboration between water utilities and spatial planning authorities. In doing so, it enriches the existing body of knowledge, as established by scientific research and grey literature. The findings outline that collaboration among the mentioned agencies can be enhanced by addressing barriers such as inconsistencies between urban water and planning master plans and the lack of training for technical staff. This would better respond to drivers like political initiatives and the implementation of national policies while also optimising tools such as collaborative design between the urban water and spatial planning sectors. The study developed in this article highlighted the importance of national policies and a legal and institutional framework that engages and motivates the various actors for the necessary climate transition. The importance of interinstitutional collaboration between the multiple stakeholders and city planning and urban water management was also highlighted as essential to foster the articulation of measures and resources among urban planning and water cycle management agencies. This collaboration can be materialised in several ways. Still, the existence of a political focus on the theme of climate change, agile and dedicated departmental structures that help to build this symbiosis, the emergence of the relevance of the theme ‘water’ in territorial management instruments and a correct involvement of the community are essential aspects for its implementation. There is also a clear need for further studies and practice on the relationship between the various actors towards a joint response to the challenges of climate change.

All relevant data are included in the paper or its Supplementary Information.

The authors declare there is no conflict.