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.