Water security determines social attitudes about dams and reservoirs in South Europe.

River barriers affect river dynamics and aquatic biota, altering the entire ecosystem. Nevertheless, dams and reservoirs provide goods like water supply and low-carbon energy that are becoming increasingly critical under current climate change. To know to what extent dams and reservoirs are important to the population, we explored social attitudes towards dams and reservoirs using a face-to-face questionnaire in two regions of contrasting climate and water security in Spain, a country with one of highest densities of dams in Europe.