Current simulations involve methane hydrates in marine-sediment clay interlayers and ab initio calculations of clay mineral structures. A central problem in subsurface hydrology is the detailed mathematical description of water flow through a heterogeneous porous formation with highly irregular layering or lensing of earth materials. This variability is reflected by a pronounced, explicit dependence of the hydraulic conductivity on spatial position at an appropriate local continuum scale. However, few models are available that are not conditioned on specific statistical assumptions about spatial variability. One useful approach to obtaining a more general model is based on the theory of dynamical systems.
Emphasis is placed on the qualitative properties of the flow.
The questions posed and settled, therefore, are global in character, applicable to a broad class of groundwater flows. No particular model of the spatial variability of the hydraulic conductivity is considered, and no hypotheses of a stochastic nature are invoked concerning spatial variability. Current topics under investigation include chaotic advection of solutes in groundwater and wave propagation through unsaturated soils. Selected Publications Martin-Neto, L., R. Rosell, and G. Sposito. Correlation of spectroscopic indicators of humification with mean annual rainfall along a temperate grassland climosequence.