The introduction of a sustainable management of freshwater resources to biological and hydrological processes of ecohydrology research by the United Nations Educational, Scientific and Cultural Organization's International Hydrologic Programme and the Man and Biosphere Programme calls for multiple and overarching philosophical explanations in ecohydrology. This paper reviews philosophical theories underpinning research in natural sciences (hydrology and biology) and social sciences, with special emphasis on studying causes and effects of ecohydrological extremes such as water stress and drought. The ontology, epistemology and methodology of theories such as Empiricism, Realism and Structurations have been considered. Specifically, the application of the hypothetico-deductive method of Empiricism was first reviewed in guiding empirical modelling of a river basin. Then, the Retroduction method of transcendental realism was also reviewed for the guidance of distributed models. Critical realism was reviewed as a philosophy of local knowledge identification of causes and effects of ecohydrological extremes. Finally, an ambitious attempt was made in proposing Anthony Giddens' concepts of resources and human agency to bridge the gap between the natural and the social science philosophies. This suggests that there can be a common grand theory for both the natural and the social sciences, and the latter can be used to validate the theoretical foundations of the former and vice versa. The study will be useful for post graduates students, especially PhD candidates, who are normally required to review and justify the philosophical foundations of their studies. Copyright © 2015 John Wiley & Sons, Ltd.