An experimental setup in Avignon (South of France) composed of an agricultural field and of a large scale undisturbed lysimeter for the multiscale study of preferential flow in soil and of groundwater recharge processes
Résumé
Preferential flow in soil is of major importance for the dynamic of groundwater recharge, on a
quantitative and qualitative point of view. This is particularly the case in Mediterranean regions
where this phenomenon is increased due to flood irrigation, high intensity rainfall events and
seasonal soil water deficit leading to soil shrinkage and cracking.
A large scale experimental setup devoted to a multiscale study of preferential flow in soil and of
groundwater recharge processes has been set up in Avignon, South of France in 2002. It is composed
of a large scale undisturbed lysimeter associated to a 0.7 ha field. Agricultural practices are the same
on both plots. The field plot is equipped with piezometers, groundwater level probes working at a
fine time step, water balance sites and porous cups for soil water sampling. The lysimeter is equiped
with soil moisture probes and tensiometers, and with an automatic device for measuring drainage
flow at the bottom of the lysimeter. Physical and hydrodynamic properties of the field plot and
lysimeter have been measured using geophysical devices (electrical tomography and electromagnetic
prospection) and the kinematic wave theory for preferential flow. Local hydrodynamic properties of
the aquifer are also known.
We present some results concerning (i) rainfall simulation on the lysimeter and on the field using
chemical tracers and water stable isotopes, (ii) drainage hydrographs obtained at the bottom of the
lysimeter under natural rains, (iii) groundwater level variations. This is an original experimental
device, combining tracers experiments, geophysical and physical monitoring of soil water and
groundwater dynamics, for studying in situ bypass flow in soil and rapid groundwater recharge at the
field scale.
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