Geoscience Reference
In-Depth Information
Electrical conductivity
Transition from one
profile to the other
during the year
A
Salinity profile A
Situation in
summer: capillary rise of salts
.
Salinity profile B.
partial
desalinization (irrigation or rains
in the rainy season)
Salinity profile D.
Process of
permanent desalinization or impeded
salinization
B
D
Fig. 13.8
Annual changes in salinity in the Camargue (Servant 1975).
Although the salts can rise in the dry season, the salinity profiles are
generally of type D when the annual rainfall is high (humid Atlantic
regions). Then the salinity increases with depth according to the leaching
of sodium by the rainwater. This is the same thing that happens in the
northern part of Algeria (Djili 2000). On the other hand, in sub-desertic
zones, the salts remain in the surface layer.
Role of the general climate
When the groundwater is saline, the process of accumulation of salts is
more marked in soils when:
Role of the groundwater
the groundwater is near the surface,
it is rich in salts,
the soil has a high hydraulic conductivity in unsaturated condition
(the salts rise more easily to the surface in loams than in sands
and in clay soils),
the P - PET is favourable for evaporation.
On a small scale (a few metres), if the land is slightly undulating and
if the soil is fine-textured, salts accumulate at the high points as shown
in Fig. 13.9 (Franzen 2005).
Role of topography
Accumulation of salts
Runoff during rainy season
Capillary rise
Leaching
Water table
Fig. 13.9
Accumulation of salts on high points when the texture is fi ne (Franzen 2005).
