The strong nonlinearity of the governing PDEs, coupled with the spatial heterogeneity and anisotropy of the subsurface media parameters, continues to pose significant challenges in mathematical and numerical modeling of subsurface flow and transport processes. These challenges become pronounced under changing climatic conditions, where increasing hydroclimatic variability and extreme events can induce rapid transitions in soil moisture and phase dynamics, flow regimes, and freshwater availability within subsurface environments. The conventional modeling approaches may struggle to adequately resolve these highly transient and nonlinear processes across multiple spatial and temporal scales. In parallel, increasing natural and anthropogenic influences are introducing a wide range of emerging contaminants, such as microplastics, PPCPs, PFAS, and other persistent pollutants, into soil and groundwater systems, whose transport, retention, transformation, and fate in variably saturated subsurface environments have yet to be studied properly. Simulating the complex interactions among these emerging contaminants, soil particles, pore-water chemistry, air-water interfaces, and biological processes further challenges the existing modeling frameworks. Besides, certain complex flow and transport phenomena in subsurface hydrology require problem-specific mathematical formulations and robust numerical strategies to obtain stable, accurate, and physically consistent solutions. This session invites contributions that advance the mathematical, numerical, analytical, statistical, and data-driven modeling of subsurface flow and transport processes. Contributions addressing methodological developments, model applications, laboratory- or field-scale investigations, and multiphysics and multiscale modeling approaches are particularly encouraged. Contributions related to the following topics, and beyond, are welcome:
● Microplastics in vadose zone – insights into pore-scale complexities and modeling strategies.
● Advanced mathematical modeling approaches for transport dynamics of emerging contaminants in variably saturated subsurface environments.
● Coupled modeling of flow, solute transport, and exchange processes between surface and subsurface systems.
● Numerical and analytical modeling of seawater intrusion in coastal aquifers.
● Numerical modeling of non-Darcian flows through subsurface media.
● Development and application of AIML modeling surrogates in subsurface hydrology.