World Water Day 2026: Green Plan for Water

Stuttgart, Germany, March 19, 2026. On March 22, World Water Day draws attention to a phenomenon that is increasingly becoming reality even in Germany: record-breaking heat waves are resulting in water shortages, while heavy rainfall is setting off destructive flash flooding with rising frequency. This is having a significant impact on the water balance and is causing the groundwater level to drop. A lot of German villages, towns and cities have already been affected by this. For Dr. Stephan Wasielewski, who heads the water infrastructure area at the consulting firm Drees & Sommer SE, a fundamental structural change is absolutely necessary: “We need to move beyond the thoughtless system of withdrawal, use and discharge. Sustainable, future-proof regions will be those that reuse water several times and keep water in circulation – this has become a key location factor for businesses too,“ the expert says.

Late summer of 2025: the Rhine River is at low water levels by historical standards; boats are stranded; delivery chains are interrupted; electricity supply and chemical production are under pressure; crops are failing; forests are burning; and insurance companies warn against incalculable risks. There is a common cause to these regional issues: it is more difficult for urban surfaces and soils to absorb and store water. Impermeable surfaces let rain run off unimpeded instead of retaining it; parched soil absorbs hardly any water when it does finally rain after long dry spells.

“This is a paradoxical problem that leads to a gradual imbalance and falling groundwater levels,” explains the environmental engineer Stephan Wasielewski, who earned his doctorate at the University of Stuttgart and has been researching and developing wastewater treatment technology, water reuse, and strategic water management for more than a decade. “There is a lack of precipitation, and when it does rain, it does not seep into the groundwater. In some areas it even causes devastating damage – a vicious circle of water scarcity and flood risk. In this way, entire regions are losing their ability to store water, and groundwater reserves are barely recovering after years of drought,” he adds.

Global Hydrological Overshoot: When Consumption Overtakes Nature

Countries and businesses around the world are currently withdrawing more water from the ground, rivers and reservoirs than natural systems can restore. Hence the United Nations (UN) has warned that the world faces ’global water bankruptcy’.[i] And Germany has been part of this trend for years. According to a study published by Boston Consulting Group and the German environmental association Nature And Biodiversity Conservation Union (NABU), the country has lost more than 60 billion cubic meters more water than the system can restore – a deficit that corresponds to the total volume of Lake Constance. Without consistent measures, the cost of inaction could amount to 625 billion euros by 2050.[ii] 

Stephan Wasielewski's work involves assisting the public sector and businesses find the best ways to deal with growing water stress. For years he has been developing solutions for the public sector and industrial firms. He has, for example, collaborated in drawing up the Water Supply Master Plan of the Ministry for the Environment, Climate and Energy Sector of the German federal state of Baden-Württemberg. Its goal is to ensure a sustainable water supply for 11.1 million people across an area of around 3.57 million hectares. The plan includes a water volume projection through 2050, detailed municipal supply maps, a systematic assessment of water supply security and customized recommendations for action for villages, towns and cities. This is the first time that a comprehensive picture of the future water supply in the federal state of Baden-Württemberg has been generated.[iii]

Industrial Sector: When Production Depends on Water

These planning tools such as the master plan at federal state level are essential for municipalities and for ensuring their water supply. This is not least because the establishment and continued operation of industry, and thus the creation and safeguarding of jobs, are particularly dependent on a reliable supply of water. Chemical and pharmaceutical companies, data centers, the food industry and the production of semiconductors – they all need large volumes of process water, in particular for cooling and cleaning processes. The manufacturing sector accounts for approximately 16 to 20 percent of annual water consumption in Germany, more than half of which is used by the chemical industry. [iv]

Requirements are also increasing: the Urban Waste Water Treatment Directive[MC1]  (UWWTD) of the European Union (EU) obliges large wastewater treatment plants to introduce a fourth treatment stage by 2045. The aim here is to reliably remove micropollutants, such as per- and polyfluoroalkyl substances (PFAS), and pharmaceutical residues or microplastics.[v]

Wastewater as a Resource

Yet Stephan Wasielewski does not view this merely as an imposition, but rather as an opportunity to fundamentally re-set industrial water management. The expert comments: ”Wastewater and rainwater are resources. However, we make little use of the available volumes today.“ Modern technologies, such as membrane filtration, biological treatment and digital control systems, are now available to enable companies to treat municipal wastewater into non-drinking water, or even into ultrapure water.

“Industrial water cycles can create a win-win situation. They ensure that everything runs smoothly, and they reduce the environmental impact,” says Stephan Wasielewski. 

“All in all, we must establish these cycles throughout the country. As long as we consume or discharge water instead of retaining it for as long as possible and reusing it several times, we will not be able to deal with the looming water shortage. We need to be thinking along the lines of a building, for example, that produces clean process water instead of dirty wastewater,” the expert continues.

Sponge Cities: How Municipalities Conserve Water – Instead of Wasting it

Most local authorities also need to rethink their approach to water issues. Ramona Jones, water and climate expert at Drees & Sommer explains: “We should not be deceived by the seemingly abundant water supply in Germany.“ She advises on projects that demonstrate how towns and cities can reclaim water. “It is important to implement climate-adapted and water-sensitive urban development proposals at this stage, before the pressure becomes overwhelming everywhere,” she adds. Municipalities determine how rainwater is managed in everyday life, and thus the resilience of entire regions. They need to retain water within the urban space and make it accessible and usable, rather than quickly draining it away as has been the case up to now.

The Lake Phoenix development in the German city of Dortmund shows how this can be achieved. Drees & Sommer’s consulting experts provided advice on the project. As an artificially created retention basin, it provides protection against flooding while also demonstrating how a former industrial wasteland can be transformed into a multifunctional working and living space near the water, that enhances quality of life. The ‘sponge city’ principle must be embedded in urban planning: a city designed to absorb water like a sponge and to retain excess water for reuse when needed – instead of letting water run off into drains as quickly as possible.[vi]

Water Level at Telegrafenberg Hill: ‘Green Lung’ at its Limit

Another example is the Telegrafenberg hill in the German city of Potsdam. In 2025, Drees & Sommer was entrusted by the GFZ Helmholtz Centre for Geosciences with the task of developing a comprehensive landscape plan. The aim was to stabilize the water balance of the long-established campus. The site acts as a green lung, a cold air lane and an important infiltration area. Many of the trees in this area are over a hundred years old. However, climate change and drought-related stress are taking a heavy toll on them. Studies show that around 78 percent of the stand has already been damaged. The sandy soil retains very little water, long-lasting periods of drought alternate periods of intense rainfall. Ramona Jones says: “The water drains away quickly or, if it can be retained, it seeps into the ground very rapidly. Either way, it cannot be delivered to the trees.“

The project team has analyzed the soil, historic structures and the vegetation. At present, the rainwater flows underground into a central trough, far from areas that urgently need water. “So the question is: how can we extract the water and make it usable? By decentralizing and distributing it across several troughs, for example, and then bringing it to the trees,” explains the water and climate expert. Digital models show how water flows across the terrain and where new storage and infiltration areas would be suitable. In parallel with this, the experts examined how the site could be encouraged to regenerate naturally, using deep-rooted species with resistance to drought and fire. These species would stabilize the trees over the long term. “The general aim is to use green spaces to bring the natural water cycle, as it exists in rural areas, back into the urban environment. And there are a lot of positive side effects, improvements to the microclimate, for instance, or the enhancement of biodiversity,” Ramona Jones points out. 

Transforming Berlin’s Schoolyards into Water Reservoirs 

Berlin’s Lichtenberg district demonstrates how also urban high-density areas can adapt to a changing climate. The local district authority commissioned Drees & Sommer to analyze how 24 schools can usefully use rainwater. A common problem for many large cities is an overstretched combined sewer system that cannot cope with heavy rainfall. The water flows away instead of staying in the district – with consequences for flooding, heat and vegetation. 

The report shows how schoolyards, roofs and green areas can be used as storage and infiltration spaces. Ramona Jones gets to the very heart of the matter: “Vegetation needs long periods of water, but climate change has made this less reliable in many regions.” She adds that this makes retaining rainwater on the land essential: not as an exception, but as the norm.

The study carried out in Lichtenberg concludes that there is great potential for improvements – but there are also structural hurdles. Many areas can be disconnected and unsealed. Hence, asphalted schoolyards can be turned into green spaces that not only retain water but also considerably enhance the quality of stay for students and teachers. 

“When looking at the issue of rainwater, a lot of stakeholders need to be involved, including all the official bodies that have a say in the matter, from monument preservation bodies to the water authority. It is very complex.“ In addition, many municipalities lack staff capacity. Funding applications tie up resources, planning conflicts with other responsibilities, and priorities shift. “But we are seeing that municipalities are increasingly becoming more active. They are also taking advantage of the relevant funding opportunities from the federal government,” comments Ramona Jones. Within the frame of the funding guidelines for measures to adapt to the consequences of climate change, for example, the Federal Ministry for the Environment has a funding program that offers support for municipal projects aimed at accelerating their climate adaptation measures.

Just like towns, cities and businesses , however, private households also have a responsibility, for example in their use of drinking water. As environmental engineer Stephan Wasielewski stresses: “Many uses do not require drinking water. Flushing the toilet, watering the garden, cleaning: rainwater and process water are good enough for this.” Using water tanks, unsealing surfaces, and installing water-saving fixtures can noticeably reduce water usage. Detect leaks at an early stage, adjust watering on the basis of soil moisture, and operate appliances in eco-mode. These are all small routine habits, but they do have an impact.” Every liter saved reduces both energy consumption and utility bills. After all, the treatment and transport of drinking water use up electricity – and as resources become scarcer, costs continue to rise. “We use drinking water like any other everyday resource. Yet it is our most valuable food. We must use other sources for all other types of use,” he adds.