In recent years numerical simulation has been adopted more frequently to study fluid flow and solute transport in subsurface environments, especially in heterogeneous soils and aquifers. The purpose of this session is to highlight recent achievements of such numerical studies, which may include newer applications in saturated, unsaturated or multiphase systems, or that include chemical reactions, other coupled nonlinear phenomena, or reference other important linkages to multi-scale problems. Papers that address analyses of particular numerical techniques and grid design, the role of Monte Carlo studies, geostatistical methods, inversion technologies, the importance of experimental design, and links to field scale experiments or larger scale models are also welcome.