This session presents recent developments in understanding, measuring, and modelling (sub)surface hydrology and solute/vapor transport processes in both, the saturated (groundwater) and unsaturated (vadose) zone, as well as across boundaries. It is well recognized that subsurface flow is an important hydrological process transporting water, nutrients and pollutants from terrestrial to the aquatic ecosystems. Quantifying such transport processes correctly is challenging since they occur at different spatio-temporal scales. Dispersion, mixing and chemical reactions are local phenomena that strongly depend on the interplay between large-scale system heterogeneity and smaller-scale processes. These processes are of practical relevance to identify the fate of contaminants in surface and subsurface water that can affect human health and the environment. In this line, subsurface runoff is the process transporting nutrients and pollutants to the aquatic ecosystems.

The aim of this session is to discuss the effect of medium and flow heterogeneity on pore up to catchment scales. We invite contributions on laboratory and field experiments, modeling, theory as well as applications. Themes include but are not limited to the applicability of macrodispersivity, mixing and reaction under spatially variable flow, the role of diffusive processes in modeling transport in porous media, transport upscaling from pore to field-scale, the relation between advection-dispersion models and dynamic structures of catchment hydrology like travel time distributions, new characterization methods of subsurface processes, advances in transport measurement and characterization techniques.