Reporter Topic: Instructive surprises in the hydrological functioning of landscapes

Reporter: Prof. James Kirchner, ETH Zurich

Time: 15:00, May.19, 2024

Location: Room 202, Academic Hall of State Key Laboratory

Brief Introduction of Report

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.