Wassertropfen fällt in ruhiges Wasser, erzeugt konzentrische Kreise.

Water Management

The increasing scarcity of water is also attracting increasing attention in Germany. We are already seeing the first signs of changing climatic conditions - through longer periods of drought or the accumulation of heavy rainfall or storms. We assume that these will become more frequent in the future. Even if there is no risk to our real estate portfolio in the foreseeable future, we are monitoring developments closely so that we can prepare our tenants and our buildings for any changes as early as possible.

For our property portfolio, there are currently no indications of immediate water-related risks, for example with regard to the supply of drinking water or the technical functioning of our buildings. Nevertheless, we continuously monitor relevant information and expert assessments on climate and water developments and incorporate them into our location and neighbourhood planning, so that we can review organisational or structural adjustments where necessary.

Management Approach

We identify water-related risks for our portfolio using both external and internal instruments. For an initial assessment, we use tools such as ENCORE and the maps provided by the WWF Water Risk Filter to identify locations with elevated risk in terms of water stress or flooding caused by heavy rainfall. In a second step, we perform a more detailed assessment using our Climate Risk Tool and the digital geoinformation portals of the federal states. The results are reviewed twice a year as part of our regular risk assessment and are documented in the risk report where relevant. For the current five-year observation period, as well as from a longer-term perspective, there are currently no material water-related risks for our portfolio.

Changing climatic conditions – such as longer heatwaves, heavy rainfall events or droughts – can affect vegetation, infrastructure and costs. Against this backdrop, we examine preventative measures aimed at limiting potential impacts and increasing the resilience of our neighbourhoods to weather events. Water is considered as a factor that plays a role in the design of outdoor areas and the management of neighbourhoods, both in terms of the usability of open spaces and operational efforts.

In the area of water management, we focus in particular on recording and controlling water consumption and on exploring options for using locally available rainwater and – where technically and legally permissible – greywater. Technical solutions such as controlled infiltration via retention areas, green roofs or infiltration basins are deployed to retain or infiltrate rainwater on-site and relieve drainage systems. Depending on location and design, such measures can also influence thermal stress in the neighbourhood and the development of vegetation. At the same time, suitable irrigation concepts can help ensure the water supply for green spaces. Our planning guideline “Sustainable Outdoor Areas” provides the overarching framework, setting out principles for the design of outdoor spaces with blue-green elements.

To further develop our approaches, we work together with specialised institutions and partners. This includes, among other things, a cooperation with the Fraunhofer Institute to plan an integrated water management system in the Bochum-Weitmar pilot neighbourhood, as well as participation in the KlimaKoop.Kommunen network, where approaches to neighbourhood development are shared and refined.

Water-related issues are particularly relevant in the residential environment and in new construction. At Executive Board level, the Chief Rental Officer is responsible for implementation in the residential environment, while the Chief Development Officer oversees new-build activities. Both areas collaborate on risk analysis, open space planning and the development of measures in order to identify location-specific challenges and plan appropriate solutions.

Our measures

Heavy Rainfall / Flooding

Heavy rainfall events can cause damage to infrastructure and buildings within a short period of time and affect the residents concerned. Our standard processes therefore include measures aimed at limiting risks and potential damage. These include, among other things, the preparation of flood risk assessments, which provide the basis for planning water management in our neighbourhoods.

When planning measures, we take into account that heavy rainfall can lead to temporarily elevated water levels. Depending on the location and technical conditions, options for managing rainwater – such as cisterns, soakaways or infiltration basins – are reviewed and implemented where appropriate. Green roofs can help delay or temporarily store the runoff of rainwater. Where local conditions permit, retention areas are also designated that can be used as temporary floodplains along watercourses.

For planned construction, refurbishment and neighbourhood development projects, water management is treated as an integral part of the planning process. The binding planning guideline “Sustainable Outdoor Areas” provides the framework, describing requirements and examples for corresponding measures.

Water Scarcity

While heavy rainfall events can temporarily exceed the soil’s absorption capacity, prolonged dry periods reduce its ability to retain water and can alter groundwater levels. Concepts for controlled distribution and temporary storage of water – for example by retaining and delaying the runoff of rainwater – are designed to take the soil’s storage and absorption capacity into account. In this context, “sponge city” approaches are discussed as a way of managing rainwater so that urban areas are relieved and local water balances are supported.

In regions with pronounced dry phases and limited water resources, appropriate land and water management is particularly important. For our property portfolio, no locations have currently been identified with a particularly high level of water-related stress. Nevertheless, we review measures that can retain or infiltrate rainwater on-site and align the design of outdoor areas with local conditions.

Typical elements of our neighbourhood water management include the use of infiltration basins and retention areas, as well as green roofs and soakaway systems. Roof drainage is planned so that rainwater is not discharged exclusively into the sewer system but – where technically and regulatorily feasible – is instead directed to local infiltration. Appropriate grading can be used to channel water towards adjacent vegetated areas. The use of permeable surfaces for paths and parking spaces reduces impermeable cover on the sites and increases the proportion of areas through which water can penetrate the soil. Retention basins can also be designed as usable open spaces, for example for play areas or structurally rich green spaces. On areas with limited infiltration capacity, additional zones are created where water can evaporate.

Efficient water use

We have only limited influence over the individual water consumption of our tenants. Ultimately, decisions on day-to-day usage lie primarily with the households themselves. We regularly inform tenants about how to use water responsibly, including through our customer magazine “zuhause”, which is published three times a year. In addition, refurbishment and conversion measures include the installation of fittings and sanitary elements designed for adjusted water flow, for example toilet flush systems or taps. Regular functional and visual inspections in our buildings help us identify irregularities such as potential water leaks and initiate maintenance work.

Wastewater from our property portfolio is discharged via public sewer systems and treated in municipal or regional wastewater treatment plants. There is no direct discharge of wastewater into oceans or groundwater.

At our office locations, sanitary facilities are designed to limit water consumption. At our corporate headquarters in Bochum, drinking water systems are available for the approximately 1,000 employees working there, meaning that daily needs are largely met via fixed dispensing points and the use of single-use beverage packaging is reduced. At our customer service location, the move from Duisburg to a new property in Essen involved a switch to modern building and sanitary technology; consumption levels are evaluated to track developments in water demand.

Our Projects

Sponge City 52° North

In Berlin-Grünau, we have developed a sustainable residential quarter on a former industrial wasteland based on the concept of the sponge city. This means that special consideration is given to the integration of biodiversity and infiltration areas.
Learn more.

KlimaKoop.Kommunen network

Vonovia is participating in a Fraunhofer ISI research and networking project with municipalities and the housing industry with a pilot neighborhood in Dortmund-Huckarde. Together with the Fraunhofer Institute, we are developing and presenting the quarter as a possible model neighborhood for measures and funding opportunities for blue-green infrastructure. Learn more.

Planning guideline for sustainable open spaces

Vonovia's planning guideline creates a binding framework for the planning, construction and operation of sustainable open spaces in Vonovia and BUWOG's residential neighborhoods. In particular, this also includes measures for the development of a blue-green infrastructure.