Geoscience Reference
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z
+
z
+
x
+
x
+
(a) t
+
= 0.013
(b) t
+
= 0.518
z
+
z
+
x
+
x
+
(d) t
+
= 4.762
(c) t
+
= 2.274
Fig. 10.4 Successive positions of the water table (dashed line) and of lines of equal hydraulic head
h
+
=
h
/
D
(solid lines), in an aquifer with
D
c
+
=
0
,
B
+
=
1
.
0, (
aD
)
−
1
=
0
.
36,
n
=
3 and
b
=
1
.
5. The indicated time values are scaled with [(
θ
0
− θ
r
)
D
]
/
k
0
. (From Verma
and Brutsaert, 1970.)
represent some aspect of the transport in the partly saturated flow zone. However, the
numerical calculations show that the effect of a change in
b
alone is very small, and also
that the calculated outflow rates are relatively insensitive to changes in
n
of only a few
units. Because
n
and
b
usually vary within a modest range for most soils, they are relatively
unimportant as compared with (
aD
)
−
1
. This is illustrated in Figures 10.7, 10.8, 10.9 and
10.10. In Figures 10.9 and 10.10 the outflow rate is shown for an aquifer whose breadth
B
+
has been increased from 1 to 5. (The saturated two-dimensional case with a free surface (see
Section 10.2 below) is shown for comparison.) Comparing these two figures, one sees that
the difference between curve 1 and 2 decreases as
B
+
increases. Thus the effect of decreasing
(
aD
)
−
1
from 0.36 to 0.10 becomes less pronounced as
B
+
increases. This suggests that in
nature, where the values of
B
+
are usually much larger than the values considered here,
the effect of capillarity is likely to be even more pronounced than these numerical results
