Theoretical basics
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9.3.1 The van Genuchten/Mualem modell
With this model the effective saturation
r
s
r
e
S
and
the unsaturated conductivity
K
in relation to the matric potential
h
are
predetermined by the following equation formula (van Genuchten,
1980):
1
/
1
)
)
(
1
(
)
(
n
n
e
h
h
S
2
1
/
1
1
)
1
/
1
(
)
(
1
)
(
1
)
)
(
1
(
)
(
n
n
n
n
n
s
h
h
h
K
h
K
Here the residual water content
r
, the water content at saturation
s
, the inverse value of the bubble point potential
[cm
-1
] and the
pore size distribution
n
[-] are the fitting parameters for the retention
function. Furthermore, the tortuosity parameter
[-] and the
saturated conductivity
are fitted to get the conductivity function.
s
K
9.3.2 The bimodal van Genuchten/Mualem Model
This model suggested by Durner (1994) describes the retention and
conductivity function by overlapping of two individual van Genuchten-
functions (Priesack and Durner, 2006).
2
1
1
/
1
)
)
(
1
(
)
(
j
n
n
j
j
e
j
j
h
h
S
,
}
]
)
(
[1
)
(
{1
]
)
(
[1
=
)
(
2
2
1
=
1
/
1
1
2
1
=
1
/
1
2
1
=
j
j
j
n
j
n
j
j
n
j
j
j
j
n
j
n
j
j
j
s
w
h
h
w
h
w
K
h
K
j
j
The
j
are indexes for the parameters of each van Genuchten
function, and
are the weights of both partial functions. The
following restriction applies:
j
w
1
0
j
w
and
1
j
w
.
