As water scarcity and climate change intensify, managed aquifer recharge (MAR) emerges as a vital strategy for sustainable water management. While its technical and environmental benefits are relatively well-documented, assessing its broader societal impacts on communities and ecosystems remains a complex challenge due to the difficult socio-economic valuation process. In other words, the success of MAR implementation goes well beyond monitoring the groundwater levels but: How to measure this achievement beyond the conventional hydrological metrics? How to easily quantify the environmental, social and economic benefits of MAR and what indicators shall be used for that?

This was the main theme of the Second EUTOPIA Groundwater Workshop and Conference organised on 12-14 March 2025 by the INOWAS Research Group on Managed Aquifer Recharge at Technische Universität Dresden in collaboration with the Research Group on Groundwater at the Department of Water and Climate at Vrije Universiteit Brussel. The event is part of the Integrated Community "Digitisation for Hydro-Climatic Risk Reduction" of the EUTOPIA University Alliance. The conference included two events, a two-day training course and a roundtable discussion, following the successful experience of the first conference in this series organised by VUB in Brussels in April 2024.

For the training course, we focused on planning and optimization of MAR schemes using the web-based groundwater modelling platform INOWAS (www.inowas.com). The platform contains several simulation tools, including a MODFLOW-based interface that enables users to setup, run and discuss groundwater flow models directly from their browsers. At first, the participants created a conceptual model that represented a specific MAR configuration, followed by its numerical implementation on the INOWAS platform and the presentation of the simulation results.

It was truly mind-blowing to witness the motivation and commitment of all participants and the strong collaboration enabled by the breakout groups among PhD and MSc students from different European universities. For such a short time, it was a great achievement to complete the design of a conceptual MAR scheme, to translate it into a numerical model and to use a completely new software to understand its impact on the underlying aquifer system. Everybody did so great and I we were very grateful to see our INOWAS platform pushed to its limits, getting also very valuable feedback and suggestions for future updates.

The conference continued over the third day with a roundtable discussion and a new list of participants. After getting busy with all the technical challenges related to MAR modelling during the first two days, it was time to leave the comfort zone behind us and glance at MAR from a totally different perspective. Splitting again in breakout groups, we reviewed the available technical, environmental, social and economic valuation tools for MAR with the aim to identify knowledge gaps and propose converging indicators and metrics that can be used for an integrated quantification of MAR societal benefits. The tasks included the expansion of the list of assessment methods, their ranking using a set of evaluation criteria (such as required data, skills, or resources, applicability across scales and sectors, application accuracy etc.), and identification of strengths and limitations of each method and their associated indicators.

Overall, the conference enabled the establishment of new partnerships and strengthened the existing collaborations within EUTOPIA University Alliance and MAR community, enabling the participants to identify shared interests, complementary expertise, and potential collaboration opportunities. During the three days, we had participants from the following institutions:

• Technische Universität Dresden (TUD)
  Institute of Groundwater Management
• Vrije Universiteit Brussel (VUB), Belgium
  Department of Water and Climate
• Freiberg University of Mining and Technology (TUBAF)
  Institute of Geology
• Dresden University of Applied Sciences (HTWD)
  Faculty of Civil Engineering
• Wageningen University and Research (WUR), Netherlands
  Public Administration and Policy Group
• Competence Center Water Berlin (KWB)
• Leibniz-Centre for Agricultural Landscape Research (ZALF)
• Martin-Luther-University Halle-Wittenberg (MLU)
  GeoEcology Department
• ERATOSTHENES Centre of Excellence, Cyprus
  Department of Environment and Climate
• University of Silesia in Katovice, Poland
  Institute of Earth Sciences
• arche noVa e.V. - Initiative for People in Need
• RANAS Switzerland
• Acacia Water, the Netherlands
• Swiss Federal Institute of Aquatic Science and Technology (EAWAG)
  Department Water Resources and Drinking Water
• Dresden Groundwater Reseaerch Center (DGFZ)

We are very grateful to the financial support provided by the German Federal Ministry of Education and Research (BMBF) and the Free State of Saxony as part of the Excellence Strategy of the federal and state governments that allowed us to organise the logistics of the conference. We are also very thankful to Prof. Marijke Huysmans and her team at the Department of Water and Climate - VUB for their visit to Dresden in such a large number, especially to Dr. Miguel Moreno Gomez for acting like a bridge between both universities. A big thank you goes also to Dr. Andre Lindner, Managing Director of the TUD's School of Civil and Environmental Engineering, to Prof. Peter Krebs, Dean of the Faculty of Environmental Sciences, to Prof. Andreas Hartmann, Director of the Institute of Groundwater Management at TUD, and to Ms. Kerstin Le Merdy, EUTOPIA University Alliance. And last but not least, to the entire team contributing the event organisation: Catalin Stefan, Serena Caucci, Falk Händel, Fritz Kalwa, and Nancy Reimann.