Urban water runoff containing pollutants poses a significant threat to both public health and biodiversity. The evolving patterns of rainfall contribute to storm overflows, exacerbating the issue, and the discovery of new contaminants further compounds the problems at hand. It is crucial for urban planners, policymakers, and water utilities to collaborate effectively in order to address and mitigate the impacts of diffuse pollution. One potential and scalable approach for mitigation involves the implementation of hybrid Nature-Based Solutions (NBS). By systematically identifying and monitoring water pollutants, their sources, and the resulting impacts, NBS can be tailored and expanded based on societal needs, policy considerations, and urban design. The collaborative efforts and insights gained from three pilot locations will play a pivotal role in advancing the development of hybrid NBS as scalable and effective solutions. A core aspect of the dissemination and communication strategy is the close collaboration with sister EU-funded projects and the organisation of clustering activities to maximise the project's impact on the target audience beyond those identified by the project. This collaboration aims to ensure knowledge exchange and transfer, co-produce and co-present joint results and policies to the European Commission and raise awareness of water-related topics. This first version of the report on Clustering Activities (D6.5) includes the actions (physical and online) that have been organised among the D4RUNOFF sister projects in the first 18 months of the projects. This document will serve as a summary and an action plan for the upcoming months for the involved parties in Task T6.5.2. Delivered in M18, it will be updated to track and measure the performed activities and the impact of the planned events. The subsequent version of the deliverable will be submitted in M42 (D6.14), while mentions of the clustering activities will also be highlighted in D6.3 (M18) and D6.13 (M42).