The last decade has seen a reformulation of the disciplinary basis of hydrology, which will be even more accentuated during the years ahead, with a dramatic increase of the intimate links between hydrology and the life sciences. We are convinced that the role of the hydrologic cycle throughout a wide range of temporal and spatial scales will be seen as a keystone in some of the most crucial areas related to biocomplexity, biodiversity, and the nature of the environment.

This book deals with the spatial and temporal linkages between hydrologic and ecological dynamics. It is a book on ecohydrology, which we define as the science that seeks to describe the hydrologic mechanisms that underlie ecological patterns and processes. The interplay between climate, soil, and vegetation is central to hydrology itself and it is crucially influenced by the scale at which the phenomena are studied as well as by the physiological characteristics of the vegetation, the pedology of the soil, and the type of climate. Ecohydrology is a key component of what are loosely called biogeosciences, in reference to the interrelationship among the biological, geophysical, and geochemical approaches to understand the earth system. Hydrologic phenomena play a commanding role in this field and hydrologically oriented research has much to contribute towards what surely will be one of the most exciting scientific frontiers of the first part of the twenty-first century.

As Peter S. Eagleson has eloquently said: