Preventing and managing diffuse pollution in urban water runoff Good quality of fresh water is essential for human wellbeing and health, for supporting healthy aquatic ecosystems and biodiversity, and crucial for agriculture and food production, three major components of the European Green Deal. Despite significant progress in reducing conventional water pollutants and improving freshwater quality, pollution loads from urban point and non-point sources remain an important challenge, particularly exacerbated in water scarce areas. Urban storm water runoff is a large contributor to diffuse pollution that impairs the quality of receiving waters and ecosystems and public health. Impacts of climate change, affecting e.g. the variability and intensity of precipitation, the concentration of pollutants and the temperature of runoff water, may further aggravate the problem.Additional knowledge is needed on sources and transport pathways of diffuse pollution conveyed by urban runoff and storm water overflows, including emerging threats and challenges posed by climate change. This accurate knowledge is essential for developing preventive and mitigation strategies focussing on source control and storm water management measures.Proposals in this field should aim to develop holistic approaches at city/catchment level ensuring resilient urban water runoff quality by considering different spatial and temporal scales and contexts, and different technologies. Urban runoff water quality management plans should consider micro-pollutants, contaminants of emerging concern, behavioural changes and societal and technical developments, including in relation to urban planning, buildings and mobility, construction and manufacturing materials, as well as sound risk management approaches. The identification and selection of measures to manage storm water quality will require engaging with relevant stakeholders, water utilities, public authorities and industry to develop guidance for decision makers and policy makers on urban runoff and storm water control measures and deploy easy and ready-made options for end users’ implementation.Actions in this topic should also aim to develop innovative and integrated concepts and technologies, including digital advances, for urban drainage systems by combining advantages from blue-green-grey solutions and decentralised approaches to preventing and managing water pollution from urban runoff and storm water overflows.In general, the participation of academia, research organisations, utilities, industry and regulators is strongly advised, as well as civil society engagement whenever necessary, also aiming to broaden the dissemination and exploitation routes and to better assess the innovation potential of developed solutions and strategies.If appropriate, applicants are advised to seek complementarities and synergies, while avoiding duplication and overlap, with relevant actions funded under Horizon 2020 calls[[Including access and use of data and information collected through long-term environmental monitoring activities supported by national and/or European research infrastructures.]], as well as targeted topics supported in the last Horizon 2020 and Horizon Europe calls, addressing micro/nano-plastics, persistent and mobile pollutants, such as per- and polyfluoroalkyl substances (PFAS), pharmaceuticals and contaminants of emerging concerns (CECs), pathogens and antimicrobial resistance.In order to better address some or all of the expected outcomes, international cooperation is encouraged.In this topic the integration of the gender dimension (sex and gender analysis) in research and innovation content is not a mandatory requirement.