The often observed processes involved in preferential water flow and c
hemical transport in porous media appear to be realistically described
using a dual-continuum (dual-porosity) approach. In this approach, th
e porous medium is conceptualized as two coexistent continua, one repr
esenting the bulk matrix and the other the macropore region. Fluid and
solute mass transfer between the two regions in the conceptual model
occurs under pressure and concentration gradients. However, oscillator
y behavior (overshoot problems in the macropore region) of the transpo
rt equation was observed fur high values of the advective solute flux
relative to the diffusive solute flux between the two regions, To circ
umvent this oscillatory behavior, the fluid coupling term in the trans
port equations was treated as an element-averaged, rather than a nodal
property. The model was extended to two space dimensions for evaluati
ng the impact of agricultural practices on solute leaching, A linear k
inetic sorption module in the transport equations and a simple plant r
oot extraction routine in the flow equations were also added. Although
the simulation results show promise, additional work will be needed t
o determine realistic model parameter values.