From Processes to Systems: A Discussion of Predictive Modelling of Flow and Transport in Geologic Systems

Much research has been done on many hydrologic processes related to flow and transport of solutes in geologic formations. Examples of these processes include dispersion and its scale dependence, matrix diffusion, flow channeling, and density driven flow. However, with the recent interest in flow and transport of contaminants or radionuclides in the subsurface as related to environmental remediation and nuclear waste disposal problems, the need is not only for an advanced understanding of these individual processes, but also for the capability of predicting such transport in the geological medium at a given site as a system. Processes like dispersion have been studied from the early days of hydrogeology while density driven flow is a clearly defined problem whose main difficulties may be technical, i.e., how to numerically calculate the process in three-dimensional complex media with sufficient accuracy. Other processes, such as flow channeling and matrix diffusion, have been relatively more recently addressed but are now well established.