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Our quantitative understanding of the terrestrial water cycle dates back to Pierre Perrault who in 1674 “measured” the water budget of a 145 km2 headwater catchment of the River Seine near Dijon, France. He showed that rainfall volume explained sufficiently the water carried off by rivers and removed by evaporation. This study demonstrated that ‘underground condensation in reservoirs’ was not needed to explain streamflow or plant transpiration—a concept previously debated since the ancient Greeks. Subsequently, the catchment water balance (inputs-outputs=change in storage) has become one of the most important equations in the geosciences. However, recent work using stable isotope tracers shows a much more complex water cycle than simple hydrometric observations suggest. At scales from global to microscopic, the water cycle appears highly compartmentalized, with much water poorly mixed at timescales well beyond the annual measurements of input and output. This talk summarizes recent work and attempts to make a case for thinking about the stored inventory of old water in our water balance accounting model.
About the Speaker: Dr. Jeffrey J McDonnell
Jeffrey J. McDonnell was born in Toronto, Canada and has a BSc (Hon) from the University of Toronto, MSc from Trent University and PhD and DSc from the University of Canterbury, where he was a Commonwealth Scholar. He has taught at Utah State University, SUNY College of Environmental Science and Forestry and Oregon State University, where he was Richardson Chair in Watershed Science and University Distinguished Professor. Since 2012, he has been Professor of Hydrology and Associate Director of the Global Institute for Water Security at the University of Saskatchewan. Jeff’s work focuses on new ways to measure, understand and model streamflow generation processes. He has co-authored >300 articles on watershed hydrology and co-edited the Elsevier textbook “Isotope Tracers in Catchment Hydrology”. He was the founding Editor of HPToday and sits currently on a dozen journal editorial boards. He is an elected Fellow of the Royal Society of Canada (Canada’s National Academy of Science), and an elected Fellow of the Geological Society of America and the American Geophysical Union. He is the 2016 winner of the International Hydrology Prize (Dooge Medal) from the International Association of Hydrological, UNESCO and World Meteorological Organization. Previously, he has received the Dalton Medal from the European Geophysical Union and the Birdsall-Dreiss Distinguished Lecturer Award from the Geological Society of America. Jeff is currently President of the AGU Hydrology Section and Visiting Distinguished Professor at Tsinghua University.