This monograph is intended to present a personal perception of the birth, evolution and consequences of a single geological concept: the gravitational systems of groundwater flow. The concept seems to have been instrumental in redefining the scope of a single-issue water-supply problem into the many-faceted earth science sub-discipline of modern hydrogeology. It has shifted the paradigm of aquifer-bound groundwater flow to cross-formational water movement in hydraulically continuous drainage basins.

This view was corroborated recently by approximately twenty-five papers presented at the Annual Meeting of the Geological Society of America, Denver, October 28–31, 2007, in the two sessions of Topic 34, ‘Regional Groundwater Flow: …’ The papers demonstrated a still lively interest in the topic 45 years after the first publication of the concept (Tóth, 1962a, 1962b), a still broadening scope of research, and an increasing variety of practical applications, as exemplified by Glaser and Siegel (2007), Gleeson and Manning (2007), Mádl-Szőnyi, (2007), Otto (2007), Rudolf and Ferguson (2007) and Winter (2007).

My perception has evolved from my own research, practical experience and literature studies in hydrogeology over 47 years (Tóth, 2002, 2005, 2007). It is presented here as a distilled summary of the relevant parts of my earlier publications, lectures and courses. I hope to summarize the results and the consequences of that work in the form of a consistent, coherent and all-round story. Illustrative case studies and case histories have been taken from my field and theoretical work as well as from published literature.