Hydrological models often lack a strong theoretical foundation, having structure and process parameterizations that are inconsistent with the understanding developed in research watersheds. In this context, this session welcomes contributions that explore the following main questions:
(1) What are major theories that can support hydrologic model development?;

(2) How can we represent small-scale processes that combine to produce large-scale fluxes (emergent behavior, space-time scaling)?;

(3) How can we make use of optimality principles (or ecological and landscape evolution principles) to constrain model behavior? Are such principles useful in an anthropogenic world?;

(4) How can we reflect the structure of the landscape in the structure of models?; and

(5) How can we develop a rigorous approach to evaluate and select among competing model alternatives in presence of highly uncertain observed data?

The intent of this session is to bring together different theories that explain individual processes, process interactions, patterns and scaling behavior; to accelerate the implementation of these theories in our models; and to discuss the testing and refinement of these theories using a mix of quantitative and qualitative analyses.