Instructive surprises in the hydrological functioning of landscapes
Colloquium
Landscapes receive water from precipitation and then transport, store, mix, and release it, both downward to streams and upward to vegetation. How they do this shapes floods, droughts, biogeochemical cycles, contaminant transport, and the health of terrestrial and aquatic ecosystems. Because many of the key processes occur invisibly in the subsurface, our conceptualization of them has often relied heavily on physical intuition. In recent years, however, much of this intuition has been overthrown by field observations and emerging measurement methods, particularly involving isotopic tracers. I will summarize key surprises that have transformed our understanding of hydrological processes at the scale of hillslopes and drainage basins. These surprises have forced a shift in perspective from process conceptualizations that are relatively static, homogeneous, linear, and stationary to ones that are predominantly dynamic, heterogeneous, nonlinear, and nonstationary.
A physicist by training, James Kirchner has worked in fields ranging from hydrology, aqueous geochemistry, and geomorphology to evolutionary ecology and paleobiology. Much of his current work focuses on the flow, chemistry, and geomorphology of mountain streams.
Until recently he was the Professor for the Physics of Environmental Systems at ETH Zurich, where he taught hydrology and environmental fluid mechanics before reaching mandatory retirement age in 2024.
He also served as the director of the Swiss Federal Institute for Forest, Snow, and Landscape Research (WSL), where he supervised a scientific staff of 550, and where he remains as a guest senior scientist.
Before coming to Switzerland, he was the Goldman Distinguished Professor for the Physical Sciences at Berkeley and the director of Berkeley's Central Sierra Field Research Stations. He is an EGU Bagnold Medalist (for fundamental contributions to geomorphology) and an AGU Fellow and Langbein Lecturer (for lifetime contributions to hydrology).
He was named by King Carl XVI Gustaf of Sweden as the Royal Professor for Environmental Sciences for 2025/26; in this capacity, he has recently been studying the ecohydrology of boreal landscapes in collaboration with SLU Umeå and the Krycklan Catchment Study.