Ignacio Rodríguez-Iturbe

2009 William Bowie Medal Winner

Princeton University

Ignacio Rodríguez-Iturbe was awarded the 2009 William Bowie Medal at the AGU Fall Meeting Honors Ceremony, held on 16 December 2009 in San Francisco, Calif. The medal is for “outstanding contributions to fundamental geophysics and for unselfish cooperation in research.”


I am honored to summarize the seminal contributions of Ignacio Rodríguez-Iturbe to the understanding of water’s role in environmental geophysics and ecology. He is the foremost surface water hydrologist in the world and has expanded the frontiers of geophysics repeatedly by identifying and opening new research areas. I will highlight what I consider to be his three principal contributions.

His work on probabilistic rainfall modeling and measuring, and network design, produced a range of widely used models of the rainfall process. He was first to provide a sound theoretical basis for sampling the rainfall process in space and time. This statistical theory accounts for the multidimensional structure of the process and provides number, location, and operating duration of ground stations needed to sample rainfall with a given degree of accuracy. The work has become a standard reference in Europe and the Americas.

His theory of the geomorphological unit hydrograph was the first to connect the geomorphologic structure of the river basin to its hydrologic response, making a major impact upon the field. It brought understanding of the streamflow response of a river basin in a generalized fashion based upon topography—the “Holy Grail” of surface water hydrologists since before the days of Robert E. Horton! Subsequently, he brought to this problem ideas from fractal theory and the growth of biological networks, leading directly to a pathbreaking book with Andrea Rinaldo, Fractal River Basins: Chance and Self-Organization (Cambridge University Press, 1997), describing landscape formation within the general framework of self-organized criticality. The work provides, for the first time, a sound theoretical basis for the way drainage basins and their networks are arranged, a necessary starting point for theories of geomorphology and for the theory of runoff. My feelings about this contribution are perhaps best expressed in the following excerpt from its foreword:

Professors Rodríguez-Iturbe and Rinaldo bring a fundamental advance to both geomorphic science and hydrologic science by uncovering and exploiting “the deep statistical symmetry” inherent in the scale-free fractal form which unifies the characterization of river networks despite their extraordinary individual diversity…the authors propose and verify a condition of minimum energy expenditure for the entire fractal network which leads to their definition of “Optimal Channel Networks.” In so doing they establish for the first time the connection between optimality and fractal growth, and offer fascinating speculation on the difference between network structures based upon minimum energy expenditure and those resulting in maximum entropy. Finally, they demonstrate that Optimum Channel Networks are spatial examples of large, forced dynamical systems which self-organize into a critical state.

In ecohydrology, Rodríguez-Iturbe is currently focusing on how plants cope with the stress resulting from a variable natural water supply. This effort has produced another pioneering book, Ecohydrology of Water-Controlled Ecosystems (Cambridge University Press, 2004), with Amilcare Porporato. It models the biophysical connections between the hydrologic cycle and plant ecosystems with a rigor that is true to both the physics and the biology, opening another field at the forefront of environmental geoscience.

To summarize, the force of his personality, together with his intellect, and his energy have made Ignacio Rodríguez-Iturbe a world leader of the movement to deepen and extend the scientific foundations of hydrology. It is indeed fitting that he receive the 2009 AGU William Bowie Medal.

—PETER S. EAGLESON, Massachusetts Institute of Technology, Cambridge


Mr. President, ladies, and gentlemen:

It is for me a great honor to receive this medal that is associated with the names of so many giants of the Earth and geophysical sciences.

When I submitted my first paper, handwritten (!), from my hometown of Maracaibo to Water Resources Research and had it reviewed and accepted, I knew how much AGU would mean to me in the years to come. That was 40 years ago, and I want to start by thanking this wonderful community of geoscientists who have always been so generous with me.

I was very lucky to do my Ph.D. under the guidance of Vujica Yevjevich at Colorado State University. Dr. “Y” created a most exciting program responsible for the first advances toward a serious probabilistic approach to hydrologic phenomena. He also taught me to dream about yet unknown problems.

Hydrology has experienced truly dramatic changes in the past 40 years, going from an appendix of hydraulics to occupying its rightful place among the other Earth sciences. I have been extremely fortunate to participate in that exciting transformation in the company of many friends to whom I will be forever grateful. Peter Eagleson, former AGU president and the last Bowie medalist from hydrology, has been my dearest friend since he hired me at Massachusetts Institute of Technology as a young Venezuelan with peculiar English. Pete has always been a source of inspiration with his fearless initiative to dive into new and unexplored questions. Andrea Rinaldo and Michael Celia have been a constant source of the most generous support not only on research but also on life in general. I have no words to fully express my gratitude to them. Whatever I may have accomplished, I owe to the best possible group of doctoral and postdoctoral students anyone could ever dream of. Here in the audience are Rafael Bras, Eric Wood, Juan Valdes, Amilcare Porporato, Paolo D’Odorico, Kelly Caylor, Todd Scanlon, Andrew Guswa, Francesco Laio, Stefania Tamea, Rachata Muneepeerakul, and Enrico Bertuzo…an unbeatable team! They are a representative sample of the outstanding excellence of many others throughout the world. To all of them I can only say thanks.

I am grateful to many academic institutions in both the United States and Venezuela that supported my involvement in areas where success was doubtful and funding was scarce. Foremost on this list is Princeton, where I found an ideal academic home where the first priority is the excitement of the intellectual search, and where my links with ecology and the other Earth sciences have brought me close to areas and problems in the intersection of the historically different disciplines of biology and physical science. It is in this intersection—where hydrology plays a fundamental role—that I believe some of the most exciting areas of research are waiting for us: hydrologic drivers of biodiversity; climate change impacts in ecosystem functioning and regional hydrologic dynamics; the metabolic understanding of river basins; and hydrologic controls of disease spread. These are just a few examples of the fascinating landscape where imaginative designs, searching for general principles and marked by a strong aesthetic incentive, will fundamentally advance our understanding of nature.

I finish these words thanking Mercedes, my wife, who has been at the center of each day of the past 45 years of my life and whose generosity in the silent acts of every day reminds me that the world needs more than knowledge: It needs the profound happiness that overcomes sadness and pain. For that happiness, for this medal that AGU so generously awards me today, and for so many other things, not only my heartfelt thanks but also my deepest love go to her.

Thank you.

—IGNACIO RODRÍGUEZ-ITURBE, Princeton University, Princeton, N. J.