Environmental Engineering Reference
In-Depth Information
-0.1
drawdown (neg) [m]
-0.2
-0.3
-0.4
-0.5
-0.6
confined
half-confined
unconfined
-0.7
-0.8
-0.9
-1
distance [m]
-1.1
0
5
10
15
20
25
30
35
Fig. 12.6
Steady drawdown of groundwater piezometric head in a confined, a half-confined and
an unconfined aquifer
pT
W
Sr
2
Q
sðrÞ¼
(12.5)
4
4
Tt
with:
Q
pumping rate [m
3
/s]
T
aquifer transmissivity [m
2
/s]
S
storage coefficient of the aquifer [1]
In the formula appears the function
W
, with an argument which is usually
abbreviated as
u
.
W
(
u
) is so important for well drawdown that it is named
well
function
in the corresponding literature. In the mathematical literature, the same
function is called the
exponential integral
and is mostly referred to as
E
1
(
u
). The
name is explained by the definition of
E
1
(
u
):
1
exp
ðBÞ
B
WðuÞ¼E
1
ðuÞ¼
dB
(12.6)
u
the well function can be found under its mathematical notation. It
is called by
expint
. In order to compute the formula given above, specify the
storage parameter
as new parameter:
In MATLAB
®