Achieving water security is a major challenge to address as we tackle climate change. This is part of the adaptation agenda, and in many water-stressed parts of the world there need to be improvements in decision-making around water resources to make adaptation more effective and equitable in policy and practice. The Grantham Research Institute is involved in a new project called ‘BASIN’ that aims to draw insights from behavioural and psychological sciences to improve decision-making in this area. Recognising that barriers and opportunities exist at multiple scales, the project will examine adaptation behaviours and practices from the individual level to the more systemic, organisational, and political levels. Such a focus on behaviour, particularly in sub-Saharan African contexts where water insecurity is still widespread, is long overdue.