Research in hydrological sciences is constantly evolving to provide adequate answers to water-related issues. Methodological approaches inspired by mathematical sciences and physical sciences have shaped hydrological sciences from its beginnings to the present day. But nowadays with the increasing complexity of hydrological phenomena, hydrological sciences have integrated approaches from the social sciences which provide missing information for the study of complex hydrological objects which is the observation and perception of water resources by users. A methodological approach: the mixed methods with their different research designs make it possible to combine the quantitative approaches of the physical and mathematical sciences and the qualitative approaches of the social sciences to understand the object of study and propose adequate solutions for its management. We detail here, the use of mixed methods in research in flood hydrology, in research on low flow conditions and on the management of these hydrological extremes. Mixed methods contributions to these studies are diverse and pragmatically relevant for hydrology. They range from the densification of data on extreme flood events to reduce forecasting uncertainties, to the production of knowledge on low-flow hydrological states that are insufficiently documented and finally to support participatory management decision-making about extreme hydrological events and water management.