Geoscience Reference
In-Depth Information
Fig. 10.8
An illustration of a rather artifi cial situation when meteorological conditions decisive
for potential evaporation (evaporativity) remain absolutely constant during a long time for a soil
initially water saturated (
θ
S
) throughout its profi le. The evaporation rate from the soil during the
fi rst stage of evaporation is constant with its value depending only upon meteorological conditions
(
top graph
). During this stage, although the soil water content at the soil surface readily decreases,
it remains close to saturation at depths not very far from the soil surface (
left part
of
bottom graph
).
The second stage of evaporation rate begins at time
t
4
(
right part
of the
bottom graph
) with an
abrupt decrease and followed by a gradually less decreasing rate illustrated in the
top graph
.
During the second stage, the soil water content at the surface remains at a critical minimum value
