Abstract
Hydrodynamic disconnectivity between surface water and groundwater is
common in arid environments. It is also prone to affect shallow streams
in wetter climate. Sediment layers with low permeability, owing to
clogging, for instance, reduce hydrodynamic connectivity. The resistance
of this clogging layer, results in unsaturated infiltration, which is
characterized by the non-linear Richards equation. Either due to lack of
field information, parsimony regarding computational resources or mere
misunderstanding of the system, infiltration is often assumed saturated
or drastically simplified in hydrogeological models. Here we show the
existence of three simple generic asymptotic solutions to the
unsaturated problem of vertical steady-state infiltration through a
clogged profile, which we associate to three regimes: one dominated by
the clogging layer, one by the underlying sediments and one depending on
both layers. We also argue that infiltration rate roughly grows linearly
with ponding depth. These observations motivate a refined definition of
clogging potentially helpful in model selection as well as two novel
approximate infiltration formulas. Our refined generic analytic
framework is useful to better understand and formalize infiltration.