Report: Healthy water cities: From sewer to health booster
The summer of 2021 became an annus horribilis in terms of extreme weather. Heavy rainfall and flooding devastated communities across the world, including Nordrhein-Westfalen in Germany, Limburg in the Netherlands, Namur in Belgium, Gävle in Sweden and Hunan in China. The high water and mud flows caused riverbanks to burst, washing away buildings in Belgium and Germany and flooding homes and streets – leading to the deaths of hundreds of people.
In rain events this epic, most drainage systems cannot withstand such volumes of water. The sewer systems, many built over 100 years ago, were therefore sorely unprepared for such extensive flooding. Moreover, sewage, grey water and water supply pipes in European cities are deteriorating, and in 10-20 years sewage infrastructure might collapse due to material failure.
Climate change – which according to IPCC’s 2021 report is alarming – and urbanisation together pose huge challenges that demand our attention.
“The increased frequency of extreme weather conditions is creating elevated health and safety risks all over Europe. Actions are needed to minimise the risks of flooding, pollution and health hazards”, says Tia Savolainen, water management engineer at Sweco Finland.
At the same time, water shortages pose a great challenge even in Europe. Without any change in water consumption, demand for water is expected to exceed available water supply by 40% in 2030 due to the growing population, increased urbanisation, climate change and a shift in our food consumption.
In the third Urban Insight report on the theme Urban Health and Well-being, we highlight the water challenges identified by engineers and designers. We spotlight the water cycle and reveal potential breakthrough innovations in underground and surface water systems that directly impact our health.
To secure a future with sufficient clean water and successful water network management that prevents system failures, we propose three water strategies that deal with health challenges at the same time: Restore space for water and people, Reintroduce nature in cities, and Reduce, reuse and purify wastewater.
The health challenges of flooding, drought and pollution
Health and safety risks are increasing across the world due to flooding, droughts and polluted water. What can we expect from the future?
IPCC’s latest report shows that scientists now have more proof than before that climate change is causing these changes in weather patterns. “Europe is warming faster than the rest of the world”, IPCC says. “No matter how greenhouse gas emissions evolve, there will be more and more intense heat”.
Dry areas will become dryer, wet areas will become wetter
In all possible climate scenarios, the intensity and distribution of precipitation is changing and the risk for heavy rainfall increasing. Regional differences in Europe show that the Nordic countries will receive more rainfall and wind with a potential risk of flooding. West and Central European regions will see more and longer dry periods during the summer months with an elevated risk of wildfires.
Drought and flooding
The intensity of precipitation may temporarily exceed the infiltration capacity, causing flooding and erosion. Together with the increased soil sealing and impermeability, lower infiltration leads to water scarcity, low river levels and pumping up of natural groundwater reserves at a rate that can no longer be reversed. In this regard, excess water must be understood in the context of water shortages. Some of the causes of water shortages are related to how we occupy and use the land, cover surfaces and provide for rain drainage before water reaches the natural water cycle.
Health-related illness, water shortages and pollution
Most of those affected by extreme heath are the elderly and low-income groups, who face consequences like premature mortality due to hyperthermia, heat-related illnesses and fires in the home. Cities are confronting water shortages and deficient public space cooling. Another problem cities face is finding space for water capture and retention, and yet another aspect is how to purify polluted runoff and surface water.
On top of water damage, the population in recently flooded areas across Europe must now grapple with sanitation problems including huge volumes of mud, fuel and chemicals that were released into human habitats and the environment. Drinking water was also polluted as underground pipes cracked and sewage water leaked into the soil.
We know what we need to do. While we need to reduce the consumption of our planet’s resources, we also need to adapt. European engineers and designers, as well as city planners and water managers, have been studying and preparing for climate change adaptation for a long time.
Strategy 1: Restore space for water and people
In the report, we touch upon three water strategies that address health challenges. In this first strategy, restoring space for water and people, people’s health can be improved at the same time.
To prevent drought as well as flooding, upstream measures are being implemented. Water capture and retention in the landscape, reopening rivers, adding water to public spaces and permeable pavement construction all represent measures that can bring back water in our living environment, with beneficial effects on our health.
Because space is scarce in dense urban areas, city planners and engineers need to look for innovative, creative solutions. But because space for water, nature, people and thriving communities is limited, we need solutions that can combine various functions. These can include rooftops for rainwater harvesting, rainwater tanks as urban furniture, floodable parking lots and squares as rainwater detention basins. Innovations and new technologies will need to take into account the extreme climate scenarios in order to provide safe and health-promoting solutions.
Extensive health effects
In the past, rivers were used as sewers and were covered to reduce the negative effects. However, due to proper sewer systems and wastewater treatment, river systems are recovering. Reopening rivers can improve the dimensions of physical, mental and social health. Reintroducing surface water in the urban context brings thermal comfort, cooling, safety improvements, views of wet vegetation and plants, access to green areas and improved recreation potential, which according to several studies all directly benefit our health. Indirectly they can make major contributions to the quality of the air we breathe through restored wetland vegetation.
Healthy blue networks
Integrated rainwater management is becoming an increasingly common practice in European cities. Open ponds, rain gardens, bioswales, urban rivers and other SUDS (sustainable drainage systems) can be restored in the green and blue networks of the city. These have a multifunctional role in the urban living environment and can provide a more pronounced evapotranspiration (heat exchange) and thus cooling effect. Studies have shown the benefits of water views and contact with water on our mental health.
Healthy water cities
Cities as well as citizens should take responsibility in shaping a healthy living environment. From private parcels to the design of public spaces, each element of the city has a role to play in maintaining the balance of the natural water cycle. Decoupling and reusing rainwater, decreasing water use and wastewater volumes are part of the solution at the parcel level.
Strategy 2: Reintroduce nature in cities
The second strategy is about using nature and soil in urban planning processes to remedy drought and flooding issues. A thorough understanding and use of the natural water cycle and natural processes not only benefits nature, but has a positive impact on people and their health. An example of this is the popular concept of sponge cities.
Safeguarding soil as water reservoirs
Our soils are challenged by flooding, water pollution and drought. Due to wear and tear on the existing network, climate change and more intense rainfall, the existing sewer system may become undersized or inadequate. A healthy soil with the right vegetation is not only important for preventing run-off, but also serves as a great water tank thanks to its vast surface and capacity to store water. It should be safeguarded to maintain water quality and the quantity of underground reservoirs, both considered indicators of our health.
Slowing the water cycle
Drought and flooding issues in the European region have the same cause: an increase in weather extremes due to a changing climate. But they are also an effect of changing land use patterns due to more drainage and more evaporation. The combination of a densely built region, high pressure on water resources and high pavement rate creates a shortcut in the water cycle, which literally flushes water as fast as possible out to the sea. As the population grows and urbanisation increases, many European governments are looking for solutions that contribute to slowing down this water cycle.
Mobilising soil teams
To address soil issues, we must first understand regional landscaping features, soil characteristics, groundwater levels and fluctuation, and natural and manmade drainage systems. Therefore, a multidisciplinary team is needed consisting of soil experts, groundwater modellers, ecologists and landscape architects who can consider the characteristics and their interdependence in order to get a clear idea of how the water system works.
The sponge effect
A sponge city is a nature-based solution that retains water at the source, slows waterlogging and flooding, and adapts the end-of-pipe system. It’s holistic and distributed and lets nature function as a resilient system that absorbs and cleans water – like a sponge.
Knowledge about managing stormwater has been around for thousands of years, and is particularly advanced with regard to monsoon climates. Chinese agricultural literature states that for every four hectares of land you cultivate, you have to reserve one hectare of land for water.
How can we turn cities into giant sponges?
To answer this question, we turned to Kongjian Yu. A professor of landscape architecture at Peking University, Yu is also an ecological urbanist, urban planner, landscape architect and founder of the planning and design office Turenscape in Beijing. So far, he has been involved in 600 projects of this kind across the world.
“People have to have a physical environment that allows us to move freely, to stretch out. We think of nature as a system. The pandemic and the lockdowns stopped us from moving and created physical and mental illnesses. The system we create in the cities allows people to move freely. Placemaking is also an important aspect of our work. For people to meet, create a community, find a cultural identity and sense of belonging”, Kongjian Yu says.
Strategy 3: Reduce, reuse and purify wastewater
The third strategy is linked to circular water strategies for reducing the exploitation of natural water resources. As our populations grow, total water consumption is increasing. By reusing water, we can decrease the volumes discharged into the rivers, which in turn will prevent flooding downstream. Our safety as well as our health can also be impacted through improved water quality.
Reduce our water consumption
To minimize the effect on our health by using water, it is important to reduce our water consumption. We can easily reduce water consumption in our households by implementing smart technology that reduces water consumption to a minimum, like buying energy-efficient washing machines, dish washers and shower systems, flushing the toilet less and buying smart taps. But our behaviour also has a major effect on our water consumption, too. Do we let the water run from the tap while brushing our teeth?
Reuse our wastewater
Another major impact can be obtained by reusing wastewater. Treated wastewater can be reused locally or from a centralised resource for applications requiring low-grade quality water, such as for toilet flushing. Nowadays, systems are even available for producing water suitable for drinking out of wastewater.
The risk of polluting sewer overflows
Due to climate change, more intense storms will occur more often. Traditional sewer systems are clogging more often, especially in urban areas with vast impermeable surfaces. Pluvial flooding and polluting sewer overflows are an increasing risk for our safety and health. A maximum integration of blue-green networks within our cities would make water management more economically feasible and therefore effectively improve water quality in outfalls.
Integrated water management tools
Besides the three design strategies, two robust tools are available for improving water management. The first is a vision as expressed in a water management plan based on European water legislation and the Water Framework Directive. The other essential tool that can help us prepare for future challenges is a digital asset management tool, which cities and water managers can use to integrate solutions and make the right decisions on budget, timing and safety.
When vision is aligned with planning
Cities throughout Europe are crafting policy documents that align their urban planning with water management plans in order to boost resiliency to water risks and better prepare for upstream and downstream impact (basin-sensitive cities). Water Plan Antwerp, Plan Bleu Lyon, Waterplan2 Rotterdam and others have sprung from visions drawn up by cities for coping with almost all water-related issues, such as flooding, water safety and the environment.
A multi-layered response
In the Netherlands, adaptation is being translated into a multi-layered approach. A first layer provides protection from flooding, with raised dikes and upstream measures. Second, when the dikes break, a bypass should protect the most vulnerable areas. And the final layer involves being prepared and having the necessary infrastructure to safely evacuate an area.
Tools for managing health in complex urban water systems
Water supply assets pose a risk to human health if not properly managed. Leaking industrial and municipal sewer systems, undersized or unsuitable water assets and the increasing effect of climate change can lead to health hazards. Leaking drinking water and sewage networks may cause water-related diseases and trigger severe environmental impacts from soil and water system pollution.
Assets shrouded in obscurity
Many are oblivious to the existence of more than 4 million kilometres of underground drinking water networks and 3 million sewer networks in Europe, which correspond to 19 trips from Earth to the moon. Another problem is a lack of understanding about the state of our assets. Some cities lack a database containing key information like the number of kilometres in their networks, or construction year, materials, location, economic value, direction of flow, volumetric efficiency, leaking probability and other metrics. The actual location of the network might not be digitalised or, in the worst case, even known. This causes problems, for example during construction or when the network lies in contaminated ground.
Maintenance and reconstruction
Infrastructure requires maintenance and investments to support healthy cities. Water infrastructure is in poor condition in Europe. Even in Finland, one of Europe’s wealthiest countries, it is estimated that 6% of the drinking water network and up to 12% of sewers are rated to be in extremely poor condition. An increase in the renewal rates of water supply networks is needed, as are other significant investments in the face of intensifying legislation and adaptation to climate change.
From reactive to proactive asset management
Asset management can no longer be purely reactive. It is vital to proactively manage infrastructure assets to ensure long-term urban health through sustainability, resilience, and security of water assets. Asset management is a systematic process that guides the planning, acquisition, maintenance, operation, renewal and disposal of property as well as information management related to finances and property.
Continuous monitoring of water quality
Real-time online water quality monitoring is also a part of asset management. Water quality monitoring ensures that the water distributed meets quality standards. It also reveals the impact of the network on water quality, providing information on the type of water pumped into the network and how it changes.
In Europe, water and wastewater systems face the challenge of doing more with less financial resources. Cities are expanding while water and wastewater assets age and water resources become scarce. Aging assets cause rising repairing costs. Water infrastructure is expensive and in poor condition in Europe because of insufficient maintenance funds. Capital investments in the sector are below the level needed to maintain the existing infrastructure.
By reacting proactively to increasing investment needs, water supply prices stay lower in the long run. This is because it is more expensive to fix an already broken system, the effects of which might be multiplied, than to carry out regular proactive maintenance so the problem will not occur in the first place.
Conclusions and recommendations
Torrential rains and floods during the summer of 2021, together with the alarming report from the IPCC about more extreme weather, are turning even more eyes towards our water supplies and water management in European cities. Our health and the health of our ecosystems largely depend on the quality of our underground and surface waters. Keeping underground infrastructure in good condition is crucial. In that sense, there is a large role for urban water engineers to play in preventing future health issues.
We need to adopt and strengthen water management in our cities. Yet our underground infrastructure is aging and in poor condition. We are facing huge costs in terms of coping with water pollution, droughts and flooding as well as the costs of rebuilding underground infrastructure.
To secure a future with sufficient clean water and successful water network management that prevents system failures, we propose three water strategies that address health challenges at the same time; Restore space for water and people, Reintroduce nature in cities, and Reduce, reuse and purify wastewater.
1. Restore space for water and people
To prevent droughts and flooding, upstream measures are being implemented. Water capture and retention in the landscape, reopening rivers, water in public spaces and permeable pavement construction are all measures for bringing back water to our living environment, with beneficial effects on our health.
Reopening river beds has the potential to store runoff excess during peaks of more frequent storms. In addition to preventing pluvial flooding, multiple health benefits are gained. Reintroducing surface water in the urban context brings thermal comfort, cooling, safety improvements, views of wet vegetation and plants, access to green areas and improved recreation potential, which according to several studies all create direct benefits for our health.
Because underground sewers are hidden from view, inhabitants are unaware of these systems and their related problems, causing a lack of political engagement to address these problems. But if rivers are restored in the visual landscape and provide more interactions, people’s engagement and relationship with our environment will increase.
In addition, a natural rainwater network (restored water cycle or an artificial underground network) can contribute to more useful water management. This also leads to a more efficient wastewater treatment system, which again would improve the quality of urban rivers and make water available for the public again.
Space for water, nature, people and thriving communities is limited, so we need solutions that can combine various functions. These include rooftops for rainwater harvesting, rainwater tanks as urban furniture, floodable parking lots and squares as rainwater detention basins.
2. Reintroduce nature in cities
A thorough understanding and use of the natural water cycle and natural processes not only benefits nature, but has a positive impact on people and their health. Environmental factors such as water quality, air humidity, sound and scents all influence our well-being, physically and mentally.
Recognising soil as a surface that has a direct impact on our water quality and water management and our most important water reservoirs complements the idea of using nature to solve future challenges in water management practices. Besides reserving space for natural infiltration, new technologies are also introducing the practice of enhanced infiltration. Enhanced infiltration processes entail capturing rain, or drained or treated wastewater, and diverting it to the groundwater layers or to surface infiltration zones.
3 ways to safeguard soil as water reservoirs:
- Minimize groundwater consumption to keep it as a strategic reserve during peak consumption or droughts.
- Refill and restore. Pavement and reduced rainwater infiltration today pose a huge challenge. Instead of leading the water through long pipelines directly to the sea, we should return to natural infiltration and keep water local.
- Prevent pollution. We must stop polluting our groundwater, for instance by keeping our sewer systems in good condition.
3. Reduce, reuse and purify wastewater
As our populations grow, total water consumption is increasing. By reusing water, we can decrease the volumes discharged into rivers, which in turn will prevent flooding downstream. Our safety as well as our health can also be impacted through improved water quality
Water consumption can be reduced by using smart new technologies. Reusing wastewater for low-grade purposes or even drinking water production will reduce our emissions and total environmental costs.
We should harvest our rainwater, or at least mitigate urban drainage, through infiltration wherever possible. Rainwater must be part of the architecture of our cities, creating places for recreation and nature experiences and increasing well-being, physical health and cognitive function. A separate rainwater collection system with a maximum reduction of water consumption and discharge would reduce the total volume of water requiring treatment. It would make water management more economically feasible and therefore effectively improve water quality in outfalls.
Embracing our relationship with water also involves keeping and using water locally for as long as possible. Rainwater resuse and infiltration in the ground will lead to a major reduction in flow discharge, preventing high economic costs for sewer systems and major buffer systems, but also preventing flooding and water scarcity during droughts.
Reusing wastewater locally helps to directly reduce water capture, production and consumption. Specific waste loads from this wastewater can be treated using more enhanced technology, leading to a reduction in surface water pollution and, again, increasing the quality of our environment and our health. Although the technology is currently available, it needs to be used in a smart way to control costs and risks. Dual networks consisting of drinking water and non-drinking water support the use of water of the right quality at the right place, helping to relieve pressure on water supplies and aging infrastructure and to address tightening regulations. This creates a window of opportunity for enhancing the reuse of rainwater and treated wastewater.
Integrated water management tools
Besides the three design strategies for cities, two robust tools are available for improving water management. The first is a vision as expressed in a water management plan. The other essential tool that can help us prepare for future challenges is a digital asset management tool, which cities and water managers can use to integrate solutions and make the right decisions on budget, timing and safety. Management software aims to help cities manage their assets, by mapping, visualizing and providing easy access to data. By reacting proactively to increasing investment needs, water supply prices can stay lower in the long run.
For more details on conclusions and recommendations, download the full report.
Healthy water cities: From sewer to health booster
About the authors
Steven Raes, bioengineer in environmental technology, Sweco, has been active in water engineering and management for more than 20 years. He has been involved in all aspects of the total water chain, with water production, water use and wastewater treatment as the point of departure. His practical experience utilises existing technologies in a new challenging and overall sustainable economic context. He starts from the broad context of the problem and determines solutions based on technical possibilities and potential risks. He is involved in projects from scope through to commissioning, all with the goal of realising a vision.
Tia Savolainen M. Sc. (Tech.) is a water supply management engineer at Sweco Finland in Tampere. Savolainen’s engineering experience includes several asset management projects in water supply companies’ risk management as well as financial and rebuilding planning. In addition, she has held operational roles in wastewater networks and sewage treatment plants, run a water supply company, and studied the chemistry of biogas rea
Demet Antakyali, Environmental Business Consulting team, Sweco Germany
Susanne Tettinger, Country project leader Urban Insight, Sweco Germany
Antti Ryynänen, business unit manager, Sweco Finland
Pekka Raukola, former development engineer Turun Vesihuolto Oy and Planning manager Sweco Finland
Michal Bucko, landscape designer, cluster BUUR, Sweco Belgium
Filip Lauryssen and Jonathan Orbie, Energy team, Sweco Belgium
Greet De Messemaeker and Annelies Beuckels, Water team, Sweco Belgium
Special Thanks To
Prof. Kongjian Yu, landscape architect, University of Beijing, Turenscape
Enrico Moens, Annette Buunen-van Bergen, Aad van Duijvenvoorde, Amanda Vierwind
Stephanie Berendsen, Sweco Netherlands
Jill Bederoff and Per Olof Lindsten, journalists
Isabelle Putseys, expert leader Urban Insight
Emma Sterner Oderstedt, Project Manager, Sweco Group
Jonathan Eriksson, Illustrator Sweco