Water Management

Management Approach

We use ENCORE and the WWF Water Risk Filter maps to obtain an initial approximate relevance assessment and identify potential risk areas in regard to water stress and flooding due to heavy rainfall. As part of a further step, we use our climate risk tool, which was developed in-house, and the digital geoinformation portals of the federal states to obtain a more precise risk assessment. The risks are reassessed by the risk owners twice each year as part of the Controlling department’s regular risk assessment and – if relevant – addressed in the Annual Report’s risk report. We do not currently foresee any water-related risks for either the five-year period covered by the company-wide risk management system or in the long-term outlook that extends to 2030 and 2050. This being the case, water-related targets and the integration of these topics into the business strategy are not (yet) relevant to Vonovia. 

Nevertheless, we are already preparing for potential climatic changes. To this end, we are working on measures that will help to mitigate extreme weather conditions in microclimates or cool urban heat islands. This requires innovative water management that can also withstand future challenges. There is significant potential in local rainwater seepage systems (based on retention basins and green roofs, for example) and using rainwater to water gardens. This potential also applies to operating costs. Our water management pursues the aims of lowering water consumption and using local rainwater and greywater. We set out our goals for a blue-green infrastructure in our planning guidelines for sustainable open spaces. 

To further develop our measures, we exchange information or cooperate with relevant stakeholder and specialist groups – for example, with NABU-NRW on the vitalization of habitats through the use of retention basins, with the Fraunhofer Institute on integrated water management planning in the Bochum-Weitmar pilot neighborhood or with the KlimaKoop.Kommunen network on establishing a holistic water management system in Dortmund-Huckarde.

While heavy rainfall events overwhelm the soil’s absorption capacity in the short term, extended periods of drought cause the groundwater level to drop, leading to a further reduction in the soil’s ability to store water. Conversely, a controlled, slow and continuous supply of water can increase the soil’s storage capacity – just like a sponge. The “sponge city” concept thus improves the water cycle and the urban climate by delaying the runoff of rainwater and reducing heat stress through evaporation. 

This is particularly important in regions that experience a high level of water stress, i.e. severe water scarcity. Even if we have not currently identified any areas in our real estate portfolio that are at such risk, introducing measures at an early stage will help to improve the urban climate and therefore people’s comfort of living. 

Typical water management measures in our neighborhoods therefore include the use of retention basins and areas as well as green roofs and other drainage systems. Water from the roof drainage systems no longer runs into the public sewage system, but is allowed to infiltrate the ground in the neighborhood itself. Planted areas around the buildings can then be watered using targeted gradient planning. The increased use of seepage paving on paths and parking lots also contributes to lowering the extent to which our land is sealed and creates more space for natural ground drainage. We make optimal use of these areas by integrating additional recreational facilities or habitats into retention basins, for example. In areas where only very limited rainwater infiltration is possible, we install additional evaporation basins.