Vadose zone hydrology and groundwater hydrology are interdisciplinary scientific fields with the primary aim to understand and describe the fate and transport of water, nutrients and contaminants in the subsurface. The scientific disciplines are closely associated with soil science, soil physics, soil and aquatic chemistry, geology, geophysics, geostatistics, microbiology, numerical mathematics and engineering, amongst others. Progress in subsurface hydrology hinges on the integration of developments in its various fields, including measurement methods in the heterogeneous subsurface, across a variety of scales.

Key problems are (among others) (1) The physics of flow in real heterogeneous, anisotropic geologic media and its coupling with chemical and biological processes to reveal how transport and transformation mechanisms contaminate and purify soils and ground water. (2) The scaling of dynamic behavior, i.e., the understanding how processes can be aggregated or disaggregated to disparate spatial and temporal scales. This is directly related to the question how the underlying dynamics can be represented in a way that can be used to generalize measurement methods for depicting the properties of complex, real systems. (3) Land surface-atmosphere interactions. Here, the focus is on understanding the reciprocal interactions between the atmosphere and soil at the land surface as a function of surface properties at several influencing scales.

This session focuses on visions and perspectives in vadose zone and groundwater hydrology, including the possibilities and problems of coupling the systems across a variety of scales. The session addresses progress and developments in modeling (numerical techniques, parameterization techniques), measurement methods, conceptual issues and scale issues. One block will focus on groundwater and one block will focus on unsaturated zone. The session consists exclusively of invited contributions.