Collaborative knowledge co-creation through citizen science and professional research involves bringing together diverse stakeholders, including members of the public (citizen scientists) and trained experts (professional researchers), to collectively generate new insights and knowledge. This approach is particularly important when addressing environmental issues as it fosters community engagement, awareness, a sense of ownership and environmental responsibility within the community. This paper discusses key lessons learned from collaborative knowledge co-creation on the Temenica River, a small Karst river in south-eastern Slovenia, particularly vulnerable to environmental change, including climate variability, land use change, water use and pollution. The paper presents a model for a small-scale, community-led environmental initiative, supported by the LEADER/CLLD method of rural development, demonstrating the power of collaboration between citizens and professional researchers - geographers in tackling water-related challenges in river communities. Various knowledge co-creation activities (workshops, focus groups, etc.) are explored, and it is shown how locals and professional stakeholders could be effectively mobilized to actively participate in data collection, information exchange, co-creation of new knowledge, producing various tools, promoting the topic and capacity building. This increased engagement of local people potentially leads to more informed decision-making in small river basin management, better resource management practices, and greater public support for environmental conservation eff orts. The paper offers insights for future eff orts to engage communities in responsible, more sustainable, and resilient river management.