The International research unit CAOS explored the link between “form” and “functioning” of eco-hydrological landscapes. The objectives were ultimately a) to improve experimental strategies such that they maximize information gain at a minimum necessary field work, b) to explore the minimum necessary complexity of process models by identifying and avoiding redundant computations using information theory and c) to understand whether changing form and functioning of hydrological landscapes is in accordance with thermodynamic organizing principles. CAOS research connected groups from Hydrology (KIT, Univ. Fribourg, Univ. GFZ Potsdam, BOKU Vienna, LIST Luxembourg) Atmospheric Sciences (Univ. Hohenheim, MPI Jena) Geophysics (UfZ Leipzig, Univ. Potsdam), Geoecology (TU Braunschweig) and Remote Sensing (LIST, KIT).

Special issue:

• Linking landscape organisation and hydrological functioning: from hypotheses and observations to concepts, models and understanding (HESS/ESSD inter-journal SI)
• Thermodynamics and optimality in the Earth system and its subsystems (ESD/HESS inter-journal SI)