Geoscience Reference
In-Depth Information
wetting of the surface by rain,
movement of water within the material (descent by gravity and
capillary rise),
drainage to the bottom of the material of the excess water not
retained,
surface drying through evaporation,
pumping of water by the roots of plants for feeding their
transpiration.
To enable monitoring of these phenomena, the material is divided
into 5-cm layers, parallel to the surface, and the hydric functioning of
each of these layers is studied. At the end of four years, the balance is
calculated (Fig. 3.1). For each layer the mean of daily water contents (as
a proportion of the maximum possible) and the annual means of hydric
fluxes (cm water that passes through these layers) are represented.
The variation in the soil water of the concentration of an ion added to
the rainwater and presumed not to interact with the solid phase (e.g.
chloride) is also calculated.
Mean annual
0
100 units
hydric fluxes
This point corresponds
annual rainfall
entering the soil
(scale in cm)
(horizontal
scale in cm,
from 0 to 100)
to the
Daily mean level of
This point
corresponds to
the annual
drainage (the
portion of the
rainfall not
retained by the
soil)
saturation
(horizontal scale in
%)
Relative concentration of
salts
(horizontal scale
of proportion of the
initial concentration,
from 0 to 100 times)
Fig. 3.1
Monitoring of the characteristic variables of hydric functioning in the profi le.
Figure 3.1 is just an example. The curves have variable shapes
according to the conditions considered, namely, the characteristics of
the climate, the vegetation and the material. But beyond these variations,
it is always observed that the anisotropy created in the vertical plane
by the positions of the source of water (the surface) and by the position
of the outlets for the water (the top, the bottom and also the middle
because of pumping by roots) is enough to create, within a physically
homogeneous material, specific layers according to moisture, drainage
