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Passive Monitoring to Determine Aquifer
Diffusivity - Time-Lag Method Calculations
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Linear regression
calculations for the representative aquifer response lag
time relationship
| Well Number |
Distance to River
(meters) |
Peak Time
(seconds) |
Time
Lag (seconds) |
Regression Distance
(meters) |
| River |
0 |
1519200 |
0 |
-45 |
| 0343 |
477 |
1674000 |
154800 |
450 |
| 0387 |
631 |
1738800 |
219600 |
657 |
| PO14 |
730 |
1742400 |
223200 |
669 |
| P008 |
579 |
1717200 |
198000 |
588 |
| P001 |
713 |
1728000 |
208800 |
623 |
| 0302 |
261 |
1674000 |
154800 |
450 |
| PO20* |
21 |
1652400 |
133200 |
381 |
| PO17* |
52 |
1638000 |
118800 |
335 |
* Note:
Not used in calculating regression line due to suspected
turbulent flow in the aquifer during flooding.
Regression
Output:
|
Constant |
-45.18692 |
|
Std
Err of Y Est |
101.15256 |
|
R
Squared |
0.880364 |
|
No.
of Observations |
7 |
|
Degrees
of Freedom |
5 |
|
X
Coefficient(s) |
0.0032 |
|
Std
Err of Coef. |
0.00053 |
Diffusivity
calculations for Monitoring Well P008
| Allow: T =
(S x² to)/(tl² 4pi) and K
= T/b |
| If x |
= 588.26
(Note: Selected distance, in meters, from river.) |
| If to |
= 928800.00
(Note: rise time of flood wave in the river was
464,400 seconds (129 hrs). Multiply by 2 for peak
decline 928,800 seconds) |
| If tl |
= 197856.00
seconds |
| If b |
= 9.14
meters |
| Then, for
these values, T/S = 0.65 m²/s |
where:
|
b |
= thickness of the saturated aquifer
at well in meters |
|
x |
= distance from the river in meters
(from regression) |
|
to |
= period of uniform stage in seconds |
|
tl |
= observed flood peak lag time in
seconds |
|
pi |
= 3.14159 |
|
T |
= transmissivity in m²/s |
|
S |
= storage coefficient
(dimensionless) |
|
T/S |
= diffusivity in m²/s |
|
K |
= hydraulic conductivity in m/s |
Transmissivity
and hydraulic conductivity calculated from assumed
storativity values
| If
S is: |
Then
T equals: |
Then
K equals: |
| 0.001 |
6.53E-04
m²/s |
7.15E-05
m/s |
| 0.002 |
1.31E-03
m²/s |
1.43E-04
m/s |
| 0.003 |
1.96E-03
m²/s |
2.14E-04
m/s |
| 0.004 |
2.61E-03
m²/s |
2.86E-04
m/s |
| 0.005 |
3.27E-03
m²/s |
3.57E-04
m/s |
| 0.006 |
3.92E-03
m²/s |
4.29E-04
m/s |
| 0.007 |
4.57E-03
m²/s |
5.00E-04
m/s |
| 0.008 |
5.23E-03
m²/s |
5.72E-04
m/s |
| 0.009 |
5.88E-03
m²/s |
6.43E-04
m/s |
| 0.01 |
6.53E-03
m²/s |
7.15E-04
m/s |
| 0.02 |
1.31E-02
m²/s |
1.43E-03
m/s |
| 0.03 |
1.96E-02
m²/s |
2.14E-03
m/s |
| 0.04 |
2.61E-02
m²/s |
2.86E-03
m/s |
| 0.05 |
3.27E-02
m²/s |
3.57E-03
m/s |
| 0.06 |
3.92E-02
m²/s |
4.29E-03
m/s |
| 0.07 |
4.57E-02
m²/s |
5.00E-03
m/s |
| 0.08 |
5.23E-02
m²/s |
5.72E-03
m/s |
| 0.09 |
5.88E-02
m²/s |
6.43E-03
m/s |
| 0.10 |
6.53E-02
m²/s |
7.15E-03
m/s |
| 0.11 |
7.18E-02
m²/s |
7.86E-03
m/s |
| 0.12 |
7.84E-02
m²/s |
8.58E-03
m/s |
| 0.13 |
8.49E-02
m²/s |
9.29E-03
m/s |
| 0.14 |
9.14E-02
m²/s |
1.00E-02
m/s |
| 0.15 |
9.80E-02
m²/s |
1.07E-02
m/s |
| 0.16 |
1.05E-01
m²/s |
1.14E-02
m/s |
| 0.17 |
1.11E-01
m²/s |
1.21E-02
m/s |
| 0.18 |
1.18E-01
m²/s |
1.29E-02
m/s |
| 0.19 |
1.24E-01
m²/s |
1.36E-02
m/s |
| 0.20 |
1.31E-01
m²/s |
1.43E-02
m/s |
| 0.21 |
1.37E-01
m²/s |
1.50E-02
m/s |
| 0.22 |
1.44E-01
m²/s |
1.57E-02
m/s |
| 0.23 |
1.50E-01
m²/s |
1.64E-02
m/s |
| 0.24 |
1.57E-01
m²/s |
1.72E-02
m/s |
| 0.25 |
1.63E-01
m²/s |
1.79E-02
m/s |
| 0.26 |
1.70E-01
m²/s |
1.86E-02
m/s |
| 0.27 |
1.76E-01
m²/s |
1.93E-02
m/s |
| 0.28 |
1.83E-01
m²/s |
2.00E-02
m/s |
| 0.29 |
1.89E-01
m²/s |
2.07E-02
m/s |
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