What is a river basin? Assessing and understanding the sociocultural mental constructs of landscapes from different stakeholders across a river basin

•We explored the spatial and sociocultural mental constructs of the river basin concept.•We combined semi-structured interviews and hand-made drawings.•We found a knowledge gap on exploring potential biases in participatory processes.•Stakeholders hold complex mental constructs related to the river basin concept.•A shared understanding is essential to conduct effective participatory processes.