New German standard for rainwater infiltration solutions

In October this year, the German Water, Wastewater and Waste Management Association (DWA) approved the regulations (worksheet) DWA-A 138-1 “Rainwater infiltration systems – Part 1: Planning, construction and operation”, which is a document of a similar level to the Latvian national standard.

Cities with significant population density face major challenges in rainwater management, especially because climate change is increasing the frequency, duration and intensity of extreme weather conditions, such as heavy rainfall and heat waves. This overloads the wastewater system and contributes to the increase in summer heat. According to the German Water Resources Act (WHG), rainwater must be managed decentrally or discharged directly into a water body using a sewage system in which rainwater is not mixed with domestic wastewater. The DWA-A 100 “Guidelines for integrated urban stormwater management” regulations set the overall goal of having as little impact on the natural water balance as possible as a result of development. Looking to the future and taking climate change into account, decentralized stormwater management is becoming a priority: stormwater is collected and used on site (if possible and permissible), evaporated, infiltrated into the soil or discharged into local surface waters, taking into account soil and water protection requirements.

History of the regulations

DWA (Deutsche Vereinigung für Wasserwirtschaft, Abwasser und Abfall) is the German association for water management, wastewater and waste management, whose role is to develop safe and sustainable water and waste management. As a politically and economically independent organization, it works professionally in the areas of water management, wastewater, waste and soil protection.

At European level, DWA is the association with the largest number of members in this field and occupies a special place thanks to its professional competence in developing regulations, educating and informing both experts and the public. The association has approximately 14,000 members, who are managers and experts from municipalities, universities, design offices, institutions and companies.

The regulations for rainwater infiltration systems have developed over a long period of time. In January 1990, the ATV-A 138 worksheet “Construction and design of systems for decentralized infiltration of relatively unpolluted rainwater” was first developed. In 2005, the regulations were revised to create the DWA-A 138 worksheet “Planning, construction and operation of infiltration systems”. The updated regulations were published for public consultation in 2019 and have now been supplemented and approved.

The DWA-A-138 worksheet provides an overview of currently known rainwater infiltration solutions that have proven themselves in practice. Information is included on the infiltration of rainwater into groundwater and the necessary hydrogeological conditions for its implementation, as well as on the necessary measures for the protection of soil and groundwater. The first part summarizes the currently known infiltration methods and systems that have proven themselves in practice, while the second part (DWA-A-138-2), which is under development, provides specific examples and practical advice.