On March 17, 2026, a German-Dutch group of professionals gathered in Gronau for the third and final workshop as part of the Cross-Border Stress Test JCAR-ATRACE – GPRW. The meeting built on the collaboration that has been in place since late 2023 and focused on jointly interpreting the results for the Vechte, Berkel, and Issel river basins and determining next steps for 2026–2027.
Joint Interpretation of Results
During the workshop, the results of the stress test were interpreted jointly: an analysis that puts the water system “under pressure” using an extreme scenario to identify vulnerabilities and potential consequences for areas such as water management, crisis management, and spatial planning decisions. Because water does not stop at the border, we also discussed how a shared understanding of upstream and downstream dependencies helps to better align risks and communication regarding them.
“The joint interpretation of cross-border map images stimulated valuable discussions and offers opportunities for a shared understanding of the system and a joint implementation agenda.”
— Angela Klein, Deltares
Technical Background
In the stress test, multiple scenarios were simulated using hydrological and hydrodynamic models. This workshop focused on the supraregional scenario of 200 mm of precipitation in 48 hours (with a wet initial condition), along with variants (including a drier initial condition or 300 mm of precipitation in 48 hours). Where possible, existing models from water managers were utilized to create the most comprehensive possible water management picture through a combination of these models. Presentations by TU Braunschweig and IfW, HKV Lijn in Water, and FloodWaive provided further insight into the technical background.
Results of the stress test
The results were presented using maps and indicators at the watershed level. Large areas could flood. Under these conditions, discharge rates could exceed historically measured levels, with potentially large-scale consequences: a total of 126 km² of urban area could be submerged by at least 1 cm, and critical infrastructure could also be exposed (fire departments, healthcare facilities, hospitals, and wastewater treatment plants). The greatest damage is estimated in the Vechte region (€3.6 billion), with significantly less damage in the Berkel river basin (€400 million).
Feedback and Action Plans
During the breakout sessions, participants divided into three groups (two focusing on the Vechte and one on the Berkel/Issel) to discuss the visualizations and how well they aligned with their expectations and local knowledge. Subsequently, they considered potential courses of action and measures. For each type of action (crisis management, spatial planning, flood mitigation measures, and water awareness), the following were discussed:
What each organization can already do with the results, which steps hold promise for GPRW and JCAR-ATRACE, and what additional information is still needed. This also led to specific follow-up points, such as utilizing the stress test results for the upcoming GPRW exercise in 2027 and as a basis for a joint action or area plan, or, in the future, establishing a link with drought to achieve a comprehensive stress test. The participants also expressed a desire to compare the 200 mm scenario with an HQ100 scenario and to calculate scenarios between these two in order to gain a better understanding of the tipping points in the system.
Next Steps
The feedback and ideas gathered will serve as input for the next steps and follow-up actions in 2026 and 2027. The organizers will share the presentation and an overview of identified measures and will distribute the final report in the second quarter with a request for feedback (a concise section covering methodology, scenarios, results, and recommendations, plus a technical background report on models and linkages). This report will also be shared in the knowledge base on the JCAR ATRACE website.
