Fundamentals of hydrodynamic modeling in porous media

The vadose zone (VZ) comprised from the unsaturated zone (UZ) and the saturated/ unsaturated interface region (SUIR) is an important link between the saturated zone and land surface. The VZ provides storage capacity for both water as one possible fluid and contaminants; a reactor medium for physical, chemical, and biological processes; and a delay time between the release of multicontaminants into the UZ and their transfer by flow of multifluids into the saturated zone. The quantitative relationship between the amount of contaminants released at the soil surface by anthropogenic activities external and/or internal to the VZ, for example, agricultural, industrial, and urban activity, and the resulting concentrations in groundwater is uncertain [6]. The UZ is believed to be with “natural attenuation” potential, which led to consider soil aquifer treatment as an efficient tertiary process for sewage effluents after secondary treatment, a technique that seemed to be a psychological projection of the granular filter methodology [7]. Qualitative decision driven from water scarcity conditions triggered in Israel the directing of rainwater falling on the roofs into the subsurface. Yet, simulations prove that in an urban environment characterized by patchworks of permeable and impervious surfaces, the underground migration of contaminants may be enhanced due to the highly nonuniform recharge of rainwater [1]. In what follows we will specifically refer to the need of accounting for nonhabitual approaches to address the modeling of hydrodynamics in porous media.