The Speaker:

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.

He received his bachelor’s and master’s degrees from Dartmouth College, and his Ph.D. from the University of California, Berkeley.  He was a member of the Berkeley faculty from 1991 through 2010, most recently as the Goldman Distinguished Professor for the Physical Sciences and Director of Berkeley’s Central Sierra Field Research Stations. 

He is currently the Professor for the Physics of Environmental Systems at ETH Zurich, the Swiss federal technical university, where he teaches hydrology and environmental fluid mechanics.  From 2007 to 2012 he 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 senior scientist. 

He became a Fellow of the American Geophysical Union in 2008.  He was the European Geosciences Union’s 2013 Bagnold Medalist (for fundamental contributions to geomorphology) and the American Geophysical Union’s 2016 Langbein Lecturer (for lifetime contributions to hydrology).

Abstract of talk:

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.

As time permits, I will also outline new methods for quantifying landscapes’ nonlinear and nonstationary behavior directly from observational data.  These methods reveal that some catchments exhibit much more nonstationary and/or nonlinear behavior than others do. They also show that some catchments exhibit strong spatial heterogeneity in their response to precipitation, resulting from spatial heterogeneity in land use and subsurface characteristics. Results from this approach may be informative for catchment characterization and runoff forecasting; they may also lead to a better understanding of short-term storage dynamics and landscape-scale connectivity.