Effective decision-making in urban water management requires integrating outputs from specialized models. Berlin’s drinking water supply relies on induced bank filtration and managed aquifer recharge from the Spree and Havel rivers. However, river inflows into Berlin are declining -e.g., in summer 2019, the Spree’s inflow was half that of an average dry summer year- and are expected to decrease further over the next decade due to the ending of coal sump water discharge into the Spree. Long-term impacts from climate change are anticipated to exacerbate this trend. Additionally, an analysis of streamflow data and bank filtrate rate-corrected groundwater extraction has identified regions where maximum monthly extractions from drinking water wells already exceed the lowest monthly river flows in Berlin. This imbalance, combined with increasing water demand driven by population growth, leads to a higher proportion of treated wastewater in Berlin’s streams. As a result, risks to drinking water quality intensify, and the complexity and costs of water and wastewater treatment escalate. Furthermore, higher extraction levels are associated with increased bank filtrate fractions, amplifying system stress and emphasizing the need for sustainable water management practices.

In collaboration with the Belin Waterworks (Berliner Wasserbetriebe), we applied a well-calibrated FEFLOW© model of the Berlin-Friedrichshagen waterworks to simulate bank filtrate rates under various recharge and groundwater extraction scenarios. The model was run under three historical well configurations (2010, 2015, and 2019) and then well pumping rates were adjusted in the same relative configuration under three groundwater recharge scenarios.

A review of prior investigations revealed groups of well galleries exhibiting similar changes in bank filtrate fractions in response to extraction levels; our results complement these former investigations. Bank filtrate behavior across well galleries was found to depend on several factors, including well depth, distance to the riverbanks, the presence of opposing riverbanks, and regional groundwater heads. Relating bank filtrate change groups to site characteristics and bank filtrate fractions in other Berlin develops a city-wide understanding of changes in bank filtrate.

Future FEFLOW© modeling scenarios, including commissioning and decommissioning of well galleries, and implementing managed aquifer recharge will be essential to address remaining uncertainties. Outputs from this modeling effort contribute to regional dynamic water balance modeling for Berlin’s semi-closed water cycle in order to support sustainable water management decision-making amid evolving climatic and regulatory challenges.

Per- und polyfluorierte Alkylsubstanzen (PFAS) stellen auf-grund ihrer Persistenz und Toxizität ein wachsendes Risiko für Wasser-ressourcen dar. In einer achtmonatigen Messkampagne wurde Regen-wasserabfluss eines Berliner Industriegebiets auf 26 PFAS und andere Industriechemikalien untersucht. Zusätzlich wurde ein urbaner See beprobt, der ausschließlich durch Regenwasserabfluss und Grundwasser gespeist wird. PFAS-Konzentrationen im Regenwasserabfluss lagen zwischen 5 und 35 ng/L, PFOA und PFHxA waren am häufigsten nachweisbar. Die Konzen-trationen lagen im Bereich vorgeschlagener Umweltqualitätsnormen für Oberflächengewässer mit Maximalwerten deutlich darüber. Im See wurden deutlich höhere Konzentrationen (bis 99 ng/L) gemessen, die vermutlich durch Altlasten des benachbarten Flughafens und nicht primär durch Regenwasserabfluss verursacht werden. Im Vergleich zu Kläranlagenab-läufen waren die gemessenen PFAS-4-Konzentrationen im Regenwasser-abfluss in dieser Studie um den Faktor 3-10 niedriger. Für Gewässer sind Kläranlagenabläufe auch durch die größeren Volumina als Eintragspfad von PFAS wahrscheinlich von größerer Relevanz als Regenwasserabflüsse. Dennoch ist Regenwasserabfluss insbesondere in Schwammstadt-konzepten mit Versickerungssystemen als potentiell relevanter Eintrags-pfad für PFAS zu betrachten. Die Ergebnisse zeigen die Notwendigkeit eines besseren Verständnisses urbaner PFAS-Quellen für ein effektives Wasserschutzmanagement.

A measurement campaign of wastewater temperatures was carried out in a section of the Berlin wastewater network. These results were used to carry out a temperature simulation using the EPA SWMM-Fork SWMM-HEAT. It was shown that a good agreement between measurements and simulations is possible for predominantly residential areas, even if the network was only moderately thermally calibrated (MAE ≤ 1 °C).

The present report summarizes the benefits of the eleven digital solutions demonstrated within DWC-WP2 in the form of fact sheets. The document aims to help cities and water utilities in finding appropriate solutions for their operational, environmental or public health deficits. The report is the final version which was submitted in Nov. 2022 after incorporating the recommendations and amendments by the EC.