Environmental Engineering Reference
In-Depth Information
15
10
5
0
0
2
4
6
8
10
12
14
16
18
20
Fig. 12.7
Unsteady drawdown of groundwater piezometric head in a confined aquifer due to
pumping according to Theis; parameters given in text, for times t
ΒΌ
10
3
,10
4
,10
5
and 10
6
S = 0.1;
Then specify the time for which drawdown is to be computed:
t = [1000000];
Calculate and plot the results by the following commands:
s = (Q/(4*pi*T))*expint(S*r.*r/(4*T*t));
plot (r,-s);
Figure
12.7
depicts the resultinmg drawdowns at four different time instants.
12.5 Automatic Transmissivity Estimation
The formulae given in the previous sub-chapters can not only be used for the
computation of the groundwater drawdown and lowering of piezometric head but
also for parameter estimation. In so called
pumping tests
water is pumped from one
well, while drawdown is observed in some surrounding boreholes or piezometers.
The result is a series of drawdown values; an example data set is given in Table
12.1
.
The conductivity or transmissivity of the aquifer is to be determined, i.e. we have
a task of inverse modeling as already introduced in Chap. 10.
