24.01.2026

Natural Cooling Through Evaporation – Planning with Water Features and Wetland Habitats

Building design

How evaporative cooling makes cities more resilient, liveable and climate-resilient

Cool Cities Despite Climate Change? With smart planning and the help of water bodies and wetland habitats, this is not just a pipe dream, but one of landscape architecture’s most efficient and elegant responses to rising temperatures. Evaporative cooling is more than just a nice byproduct—it is a strategic tool for sustainable, livable, and resilient cities.

Natural Evaporation as a Key Mechanism for Cooling Urban Spaces
Planning Principles for Integrating Water Bodies and Wetland Habitats
Scientific Findings: How Water Bodies Influence the Urban Climate
Practical examples from Germany, Austria, and Switzerland—from successful riverside parks to innovative “sponge city” concepts
Challenges and obstacles to implementation: competition for land, maintenance requirements, water quality
Synergies with biodiversity, stormwater management, and urban livability
Technical and Legal Framework for Planners and Municipalities
Strategies for promoting acceptance and civic engagement
The role of monitoring, digital twins, and simulations in evaluating success
An Outlook: Why Evaporative Cooling Must Become the Backbone of Climate-Resilient Urban Planning

Evaporative cooling—the underestimated powerhouse of urban planning

Anyone who has ever rushed through a paved-over city center in the summer with a flushed face, only to feel the refreshing relief of a city pond, fountain, or shaded wetland, has experienced it firsthand: the natural power of evaporation. But what is often perceived in everyday life as a pleasant background sound is, in reality, a highly effective physical process that gives smart planners a powerful tool to protect against urban overheating. Evaporative cooling is based on the fact that when water transitions from a liquid to a gaseous state, it absorbs energy in the form of heat—and draws this heat away from the surroundings. It may sound like something out of a textbook, but it is the urban issue of the future par excellence.

The effect is no small matter: large bodies of water and wetland habitats not only provide localized cooling but also influence the microclimate of entire neighborhoods. They create islands of cool air, promote nighttime ventilation, and thus act like natural air conditioners. Unlike technical cooling systems, they require little maintenance, operate silently, and rely on an energy source that never runs out: solar heat. What has long been standard practice in Asian megacities is also gaining increasing attention in Central European cities—at least since the summer heat has been breaking new records here as well.

But evaporative cooling is not a magic bullet that can simply be turned on at the push of a button. It is the result of careful planning, hydrological analyses, and a healthy dose of courage to experiment. After all, every body of water, every wetland, behaves differently: shallow or deep? Still or flowing? Shaded or exposed to the sun? The parameters are numerous—and the right combination of them determines success or failure. For planners, this means that anyone who wants to cool using evaporation must understand and manage the complex interactions between water, soil, vegetation, and the atmosphere.

The key lies in integration. Water bodies are most effective when they are embedded in an overall concept that also includes green spaces, fresh-air corridors, and infiltration areas. The famous “sponge city” is not just a marketing gimmick, but describes precisely this approach: viewing cities as permeable, living systems that store, evaporate, and cool water. If this is achieved, the result is not only cooler but also more livable, species-rich, and resilient urban spaces.

Another advantage: evaporation areas are versatile. They not only improve the urban climate but also provide habitat for animals and plants, promote biodiversity, trap particulate matter, and can even contribute to rainwater management. This multifunctionality makes them one of the most efficient tools for sustainable urban development—provided they are planned consistently and professionally.

The challenge, then, is not “whether” but “how”: How can water bodies and wetland habitats be integrated into the city in a way that allows them to reach their full potential? And how can we gain acceptance among policymakers, administrators, and the public so that evaporative cooling becomes more than just a fig leaf for modern urban planning? Answers to these questions can be found by examining the scientific foundations, successful practical examples—and the stumbling blocks that can cause even the best concepts to fail.

Planning Fundamentals: Properly Sizing and Designing Water Bodies and Wetland Habitats

Anyone planning water bodies and wetland habitats faces a dilemma: On the one hand, the facilities should generate as much evaporative cooling as possible; on the other hand, municipalities and investors are competing for every square meter of usable space. The solution lies in the precise selection of location, size, depth, and surrounding vegetation. Scientific studies show that shallow, well-sunlit water bodies in particular have a high evaporation rate—though they also dry out more quickly and, in extreme cases, can become a source of heat when water becomes scarce. This requires a keen understanding of hydrology.

A key consideration is integration into the local water cycle. Ideally, water bodies and wetland habitats are fed by rainwater collected from roofs, paths, and open spaces. In this way, planners kill two birds with one stone: they relieve pressure on the sewer system during heavy rainfall and ensure that the evaporation areas do not become fallow even during dry summers. However, this requires intelligent control of the water supply—keyword: retention management. Digital tools and sensor technology can help regulate water levels according to demand and minimize losses.

Proper design is crucial. While a sprawling lake may look impressive, it is often problematic to maintain and care for. Smaller, modular wetland habitats and cascade systems offer greater flexibility and can be more easily integrated into densely populated neighborhoods. Riparian zones with reeds, grasses, and perennials not only enhance biodiversity but also act as natural filters and ensure a stable water balance. In addition, they offer a pleasant environment and invite people to relax—a factor that should not be underestimated when it comes to acceptance within urban society.

The technical design depends on local conditions. In historic city centers with narrow property lines, creative solutions are often required: evaporation basins along streets, planted rooftops with water reservoirs, or temporary wetland habitats on vacant lots. In new development neighborhoods, on the other hand, spacious ponds, streams, and retention areas can be planned from the outset. It is important that these features be understood not as isolated, individual measures but as part of an overarching open-space system—only in this way can a cohesive cooling network be created.

One aspect that is often underestimated is maintenance. Water bodies and wetland habitats require regular monitoring to prevent silting, algae growth, and pollution. Here, it is advisable to collaborate with specialized companies and—where possible—to involve committed citizens. Technical innovations such as automatic water level regulators, floating islands, or near-natural water purification systems can minimize the effort required and ensure the longevity of the facilities.

Ultimately, the early involvement of all relevant stakeholders—from water authorities and landscape architects to future users—is the best guarantee of sustainable success. Only in this way can solutions be developed that are effective and enduring not only on paper but also in everyday life.

Science and Practice: How Water Bodies Really Influence the Urban Climate

The impact of evaporation areas on the urban climate has been better researched today than ever before—and the results are impressive. Measurements taken at urban wetland habitats show that the ambient temperature can drop by up to five degrees Celsius in the summer. What matters is not only the absolute area but also the spatial arrangement: water bodies strategically located along fresh-air corridors or in wind-exposed areas distribute the cooling effect particularly effectively throughout the urban space.

The cooling effect is based on several physical processes. On the one hand, evaporation removes heat from the air; on the other hand, it increases humidity—which is perceived as pleasant during hot weather but can lead to increased fog formation in winter. Planners must therefore keep seasonal dynamics in mind and, if necessary, incorporate seasonal control mechanisms. In combination with trees and shrubs, this creates veritable “cooling corridors” that divert hot air masses and provide fresh breezes.

Another benefit: bodies of water act as giant thermal buffers. They absorb solar energy during the day and slowly release it at night. In this way, they prevent extreme temperature fluctuations—an important factor for the health of both people and vegetation. In densely built-up neighborhoods, where concrete and asphalt heat up during the day and barely cool down at night, wetland habitats create a welcome buffer zone.

Evaporation areas also have a positive impact on air quality. They trap dust, filter pollutants, and promote air circulation. Studies in cities such as Zurich, Vienna, and Hamburg show that the quality of life near bodies of water increases significantly: less heat stress, greater biodiversity, and better recreational opportunities. No wonder, then, that more and more municipalities are making targeted investments in the enhancement of waterfront areas, park ponds, and artificial wetlands.

Modern planning tools such as digital twins, climate simulations, and monitoring systems now make it possible to precisely calculate and visualize the effects of evaporation areas in advance. On this basis, various scenarios can be simulated—such as how an additional urban pond would affect the microclimate of a new residential development, or which combination of water and green spaces would provide the greatest cooling effect. The data obtained is an invaluable asset not only for planners but also for policymakers: it makes the impact of investments measurable and transparent.

Despite all these advantages, there are also limitations. The effectiveness of evaporative cooling depends heavily on the local climate zone, wind conditions, and the surrounding buildings. In narrow urban canyons with little air exchange, the cooling effect can be lost, while impressive results can be achieved in open parkland settings. For planners, this means that every project requires a customized solution that takes specific site factors into account and responds flexibly to changing conditions.

Challenges and Innovative Approaches: Striking a Balance Between Aspiration and Reality

As compelling as the arguments for evaporative cooling may be, putting them into practice is often a balancing act. Competition for land, cost pressures, maintenance requirements, and legal hurdles frequently stand in the way of the “sponge city” ideal. Especially in inner-city areas, where land is a precious commodity, planners must find creative solutions to integrate water bodies and wetland habitats without sacrificing urgently needed development space. This calls for multifunctional open spaces that combine cooling, stormwater management, and quality of life.

One example of innovation is temporary wetland habitats that are activated during heavy rainfall events and serve as play or recreational areas during dry periods. Modular water storage systems that can be flexibly adapted to demand are also gaining importance. Some cities are already testing planted “floating islands” that drift on existing bodies of water and provide additional evaporation and filtration capacity. Such approaches demonstrate that technical ingenuity can further increase the effectiveness of evaporation areas—even in limited spaces.

A perennial issue is the question of water quality. During hot weather, stagnant bodies of water are prone to algal blooms, siltation, and foul odors—a nightmare for residents and urban planners alike. The only solutions here are consistent monitoring, preventing nutrient-rich inputs, and the use of near-natural purification systems. In some cases, targeted water exchange with flowing water bodies or groundwater can also be beneficial—provided the legal requirements are met.

Another obstacle is public acceptance. Not everyone finds open water bodies attractive—fears of mosquitoes, accidents, or the maintenance required are widespread. This calls for communication skills and public engagement. Community workshops, information campaigns, and participatory planning processes help to dispel reservations and foster a sense of connection. In Vienna, for example, new “sponge city” neighborhoods were developed from the outset in collaboration with residents—with resounding success.

Finally, the legal and technical framework must also be in place. The Water Framework Directive, nature conservation laws, land-use regulations, and local ordinances set strict limits but also offer room for innovative solutions. Planners and municipalities that want to succeed need not only expertise but also negotiating skills and perseverance. The good news is that an increasing number of funding programs, guidelines, and networks now support the implementation of nature-based cooling concepts—from the initial idea to the finished system.

Perhaps the most important factor for success, however, is a new way of thinking: moving away from purely land-use management toward dynamic, interconnected systems that view water, vegetation, and people as a single unit. Those who embrace this paradigm shift have the best chance of ensuring that evaporative cooling does not remain merely a nice bonus, but becomes the backbone of climate-resilient urban development.

Conclusion: Evaporative cooling—the backbone of tomorrow’s urban planning

The integration of water bodies and wetland habitats for natural cooling is far more than just an ecological trend. It is a necessity in the face of climate change and increasing urbanization. With smart planning, technical innovation, and public participation, impressive benefits for the urban climate, biodiversity, and quality of life can be achieved. The challenges are real but solvable—provided that policymakers, administrators, and planners work together and recognize evaporative cooling as an integral part of modern urban development.

The future of urban spaces is not only built but also modeled, simulated, tested, and continually adapted. Water bodies and wetland habitats are more than just decorative accents—they are the backbone of a resilient, livable city. Those who invest in evaporation today will gain a decisive advantage tomorrow in the fight against the heat. And best of all: City residents will appreciate it not only on the hottest days of the year—but day after day, year after year.

22.04.2025

Architecture

44 residential units in Saint-Denis from DREAM

Building design

The new building with 44 residential units by DREAM. Photo: Cyrille Weiner

Two decades after the devastating fire in a dilapidated residential building on Rue Fraizier in Saint-Denis, a new construction project marks a turning point in the urban development of the north of Paris. The Parisian agency DREAM (Dimitri Roussel) has realized a residential ensemble with 44 units there – half for rent, half as subsidized ownership according to the “Bail Réel Solidaire” (BRS) model. It is the first project of its kind in Saint-Denis. However, the ambitious gesture is less about architectural showmanship and more about functional, mass-produced housing that strives for social integration.

The new building stands on a site that has been derelict since the fire in 2001. The fire at the time drastically exposed the dilapidated conditions in the old building, which was being used by shark tenants. The ensuing vacancy was perceived not only as a physical defect, but also as a social one. DREAM now sees the project as a contribution to “repairing” the neighborhood – and to re-establishing trust in the urban space.

The 44 residential units are spread across several buildings and follow a clear principle: as much individuality as possible within the standardized production. Almost all of the apartments are open-plan, with many facing in several directions. The majority have generous outdoor spaces – balconies or gardens at ground level. Interior qualities have also been considered: separate entrance areas with storage space, daylight kitchens that can be closed off if required and large window openings with panoramic views are all part of the repertoire.

The floor plan design is based on the charter of Plaine Commune, the inter-municipal association responsible for the area. The urban positioning of the buildings responds to morphological and climatic analyses of the site. A typical planning response is, for example, the staggering and orientation of the volumes to optimize daylight and natural ventilation.

In terms of design, DREAM dispenses with design experiments. Instead, the architectural expression arises from the materiality and rhythm of the façade. Wooden slats, metal panels and open balcony structures made from a combination of wood and metal structure the outer shell. Great importance was attached to prefabrication: The timber frame construction walls, including cladding, windows and shading elements, were manufactured entirely in the factory. The self-supporting balconies also arrived on site pre-assembled.

This strategy has several advantages: Firstly, it increases the quality of execution, and secondly, it reduces the construction time – a factor that plays a particular role in the densely built-up and socially sensitive Saint-Denis. All in all, the result is a residential building that relies on CO₂-reduced construction methods without playing this off visually.

What is striking about the project is the effort to establish communal zones alongside the private living space – a concept that is often referred to elsewhere as “third places”. In Saint-Denis, the elements are simple but effective: a large, inviting entrance area, green inner courtyards with passageways and roof gardens that serve as places to retreat and meet. The lobbies act as semi-public buffer zones between the street and the apartments. Visual references to the courtyard are intended to provide not only light but also social control.

The whole project was designed in collaboration with the public housing association Plaine Commune Habitat. The aim is to appeal to a heterogeneous group of residents – both people on low incomes and young families who want to build up property through the BRS model.

With a construction cost of around seven million euros and a living space of 2,775 square meters (SHAB), the project is within the scope of what is feasible in a subsidized context. The “NF Habitat” certification and compliance with the French thermal insulation regulation RT 2012 with a 20 percent reduction underline the ecological focus.

Those involved in the project include Bollinger+Grohmann (structural engineering), ENEOR (building services), Le Sommer (certification) and Topager for the landscape architecture. Cap-Exe was responsible for coordinating the various trades.

What can be deduced from the project in Saint-Denis for the current housing debate? Certainly not a new type. Rather, it shows how a combination of solid planning, serial production and municipal control can make a contribution to sustainable urban development – beyond creative exaggeration, but also without falling into banal functionality.

The architecture remains restrained but deliberate. It unfolds its effect through everyday use – as a place to live, to meet and to reappropriate a long-neglected urban space.

31.10.2024

Ukraine war: Мы за мир

Building design

As a result of the war in Ukraine, the European architecture scene has quickly taken a public stand against the Russian war of aggression. G+L also stands in solidarity with the Ukrainian people and government.

BIG, David Chipperfield Architects, Foster + Partners, gmp, Herzog und de Meuron, MVRDV, OMA, Snøhetta, Zaha Hadid Architects – as a result of the war in Ukraine, which violates international law, the who’s who of the European architecture scene publicly opposed the Russian war of aggression in a very short space of time at the end of February/beginning of March 2022. Within just a few days, numerous offices expressed their solidarity with the people in Ukraine and with all those who stand for peaceful coexistence – above all via social media. In the case of Chipperfield, HdM, OMA and Zaha Hadid, the public statements were followed by an immediate halt to all construction projects in Russia. BIG also announced in a statement that the office would not be carrying out any projects in Russia or for the Russian government. However, it is not clear from this whether a construction freeze has been imposed or whether there are simply no Russian projects currently in progress.

First the governments, then the private sector. Today, our globalized world also makes it possible for corporations, companies or even planning offices to impose sanctions. So while Apple, Siemens, Starbucks, McDonalds, Coca-Cola, Pepsi and the management consultancies KPMG, PWC, EY and Deloitte are suspending their business in Russia as a result of the war of aggression, or Elon Musk is actively supporting Ukraine with the help of his satellite internet service Starlink, including reception systems, the world of architecture is also drawing its own conclusions. This is worth a special look, as it was or is precisely non-democratic regimes such as Russia or China that have provided the big star offices with unique construction projects in recent years. The M+ Hong Kong designed by HdM only opened at the end of 2021. While at the turn of the year in Moscow, the Renzo Piano Building Workshop RPBW converted the GES-2 power station into a center for visual and performing arts for the V-A-C Art Foundation.

Jacques Herzog on democratic architecture

For us in the editorial team, this immediately (and once again) triggers the question of how political planning can be, but also how political planning must be. What is exciting in this context is that Jacques Herzog in particular has repeatedly publicly addressed the question of democratic architecture. You can think what you like of him and the HdM projects, but he takes a stand. As he did in an interview in 2020 with Lukas Gruntz from architekturbasel.ch. Referring to the historic urban development of St. Petersburg, Venice, Rome and Paris, he said here: “Perhaps more beauty is created in a non-democratic context because the context is more extreme, more radical.” But he also continued: “From our point of view, an enlightened and democratic society, architecture must be anchored in the population and ideally emerge from the needs of the population.” Sentences that should make us think. Now more than ever.

Ukraine war: Coop Himmelb(l)au under pressure over Crimea project

Lighthouse projects in non-democratic regimes must be better considered in future. I wonder what is going through Wolf D. Prix’s head at Coop Himmelb(l)au right now? His office was criticized even before the war of aggression. Since 2020, the Viennese have been planning two of the four cultural buildings that Vladimir Putin wants to be built by 2023. The particularly tricky case is the planned opera house on the Crimean peninsula, which was annexed by Russian occupiers in 2014 in violation of international law(more on this in an SZ-Plus article). With reference to the lighthouse project, Ukrainian President Volodymyr Zelensky imposed economic sanctions against the Viennese architecture firm and six of its representatives on January 21, 2022.

Wolf D. Prix: Coop Himmelb(l)au is building an opera house, not barracks

According to an SZ.de article by Gerhard Matzig, who interviewed Prix on the subject, this was preceded a year and a half ago by threats from the Ukrainian embassy to Coop Himmelb(l)au. Prix would not be allowed to build the opera house in Sevastopol or the architectural firm would soon be ruined. And according to Gerhard Matzig in his article, Prix has now also been advised to distance himself from the project and Putin. When asked by Matzig whether he would do so, Wolf D. Prix sighed on the phone. Prix is of the opinion that he is not building a barracks, but an opera house. As a cultural project, this is not subject to the embargo regulations. Unsurprisingly, as of mid-March 2022, Coop Himmelb(l)au still has no statement on the Ukraine war.

Ukraine war: Russian planners make their mark

But now back to those who openly oppose the war. Because it’s not just the European star offices that are flying the flag. According to SZ.de, a total of 6,500 Russian architects, designers and urban planners also signed an open letter on the website of the Russian architecture magazine “Project Russia” between February 26 and March 4, 2022, calling for an immediate end to the war. The tragedy is that this appeal also fell victim to the “fake news” law against critical reporting on the Russian army signed by Vladimir Putin on March 4, 2022. Only a short version of the campaign with a picture of a dove of peace can now be seen on the site. It says here in Russian: “Unfortunately, we were forced to remove the text of the letter under threat of criminal liability under the law that came into force today. We are for peace!”

One profession, one passion

Meanwhile, however, the Union of Architects of Ukraine also called on the International Union of Architects to expel the Union of Architects of Russia from the organization. “Those who do not condemn Russia’s actions support them,” the Süddeutsche Zeitung quotes the President of the National Union of Architects of Ukraine, Oleksandr Chyzhevsky, as saying in a letter to the UIA. If you let this statement sink in, you have to ask yourself – even if you condemn Russia’s actions in the strongest possible terms – whether we really want to live in a world in which people from one industry, one profession, one passion, go against each other simply because of their nationality. For this very reason, the G+L editorial team would like to join our Russian colleagues: Мы за мир. We are for peace. And we condemn the Russian government’s attack on Ukraine, which violates international law, and stand in solidarity with the Ukrainian people and government.

Ukraine war: bdla and BAK also active

While German landscape architecture firms are still quite reluctant to express their solidarity, the bdla published an official solidarity statement #StandWithUkraine on March 2, 2022. The bdla declared its “deepest regret about the war in Ukraine, the loss of human lives.” It condemns this attack, which violates international law. The bdla’s thoughts are particularly with its colleagues from its partner association, the Guild of Landscape Architects of Ukraine. In the same letter, the bdla refers to the initiative of the Federal Chamber of Architects. This has set itself the goal of becoming active beyond expressions of solidarity. For this reason, the BAK is making its network available to the Ukrainian Association of Architects. The goal: sleeping places for refugees. Find out more here.