Overview | Energy and the Earth System | Land Surface Dynamics | The Diverse Biosphere

Catchments as Organised Systems

The overall aim of the DFG-funded research unit From Catchments as Organised Systems to Models based on Functional Units (FOR 1598) or CAOS is to provide a new framework for building hydrological models that allow a much more realistic representation of the surface and especially subsurface architecture of catchments at the lower mesoscale (10–200 km2). Key methodological objective is to unite a) the recent observation and exploration technology from soil physics, geophysics, remote sensing and hydrology with b) our understanding of landscape formation and soil structure development and c) reductionist process models as learning tools to assess novel information on surface and subsurface structures as well as on distributed process dynamics. Key theoretical objective is to develop a model and mathematical framework that allows better integration of this information into the model identification process and thus facilitates communication between experimentalists and modellers. Research will be conducted in the hydrological observatory “Attert basin” that has been operated by the Gabriel Lippman Research Institute in Luxemburg since 2003 and is among the best investigated basins in the World.

Our contribution is to investigate the use of optimality principles to better describe and predict the effects of spatial patterns and temporal dynamics of the structural soil and vegetation properties that modulate soil-vegetation-atmosphere transfer (SVAT). In particular, it will compare biologically motivated principles (e.g. the maximum net carbon profit hypothesis) with thermodynamic principles (e.g. the maximum entropy production (MEP) hypothesis). The project will also analyse the relationship between free energy dissipation, work and entropy production in the context of heat, water and carbon exchange to put the applicability of the MEP principle into perspective with the use of free energy for self-maintenance of living systems.

As part of the means to achieve these aims, a soil-vegetation-atmosphere transfer (SVAT) model will be developed that (a) simulates a range of observable and hydrologically relevant vegetation properties, (b) integrates with the overall model of the CAOS research unit, (c) allows the calculation of all the relevant thermo-dynamic properties of the system and (d) optimizes different thermodynamically and biologically motivated goal functions. An efficient implementation of optimization and thermodynamic diagnosis in the model will be a major part of the model and methodology development.

Finally, the model results will be compared with a range of available observations to test the utility of the different proposed organizing principles for hydrological prediction.