Event name: PhD Symposium on subsurface hydrology in land surface models
Event dates: 25th Nov. 2016
Event location: Forschungszentrum Jülich, Building 14.6, Room 241

Prof. Dr. Sascha Oswald and Dr. Rafael Rosolem were invited to give talks at the PhD Symposium of Roland Baatz on ‘Subsurface hydrology in land surface models’. The presentation stressed the relevance of field scale observations for improved understanding of land surface processes. The talks were introduced by Prof. Dr. Harrie-Jan Hendricks Franssen (FZ Jülich) head of the research group on ‘Stochastic analysis of terrestrial systems’.

Prof. Dr. Sascha Oswald is a full professor at the Institute for Earth and Environmental Sciences at University of Potsdam. He received his Ph.D. in Environmental Sciences from the ETH Zürich in 1999. After working as physicist at Colenco Power Engineering, research fellow at University of Sheffield, senior assistant at the Institute for Terrestrial Ecology at ETH Zürich, he became senior researcher at the Helmholtz Center for Environmental Science, UFZ Leipzig, in 2004. From 2009 onwards, Sascha Oswald became Professor for Water and Matter Transport in Landscapes at the University of Potsdam.

Dr. Rafael Rosolem is Lecturer in Water and Environmental Engineering at the University of Bristol. He received his Ph.D. in Hydrology from the University of Arizona in 2010. He became research associate and research assistant Professor at the University of Arizona and worked on the COsmic-ray Soil Moisture Observing System (COSMOS) project. From March 2013 onwards, Rafael Rosolem joined the Faculty of Engineering at the University of Bristol.

Rafael Rosolem introduced novel results on the representation of preferential flow paths in a chalk aquifer in a catchment scale land surface model. The presented study revealed the influence of chalk hydrology on land surface processes. The subsurface of the Joint UK Land Environment Simulator (JULES) was parameterized with an additional model to account for water flow in macro porosity. Simulation results were compared from field and remote sensing measurements in the Kennet catchment in Southern United Kingdom. The presentation was followed by a discussion on available methods for measurement of land surface variables relevant at the catchment scale.

Sascha Oswald introduced novel methods for snow depth observations and root water concentration measurements. The Cosmic Ray Neutron Sensing method was used to measure neutron intensity at a high altitude Alpine observation site. Neutrons are moderated by hydrogen which allows the observer of neutron flux to draw conclusions on the presence of water and snow in the vicinity of a Cosmic Ray Neutron Sensing device. Snow depths was measured at the point and field scale using single point laser beams and laser altimetry (LiDAR), respectively. Observed neutron flux decreased exponentially with increasing snow depth even if snow depth was several decimeters high. The observations were used to derive an empirical model to determine snow depth at the field scale from neutron flux measurements. The second part of the presentation used neutron flux measurements to monitor water concentration within roots at the laboratory scale. The experiment was conducted in a laboratory under controlled conditions. Plants were grown in a specially designed box, which was illuminated by neutron beams. The monitored neutron flux allowed the observer to induce the location and water saturation of plant roots within the examined box. The neutron tomography of water migration within plants allows soil and plant physicists to quantify drivers and processes for plant water uptake.

These presentations were followed by a reception to commemorate the successful PhD defense of Roland Baatz. The symposium was well received by participants from the Agrosphere Institute and the TR32 with intense discussions on challenges and opportunities in land surface modeling and observation.