Question

In a field test, a time of 6 hr was required for a tracer to travel between two observation wells 42 m apart. If the difference in water table elevations in these wells are 0.85 m and porosity of the aquifer is 20%, then coefficient of permeability of the aquifer is ___________ mm/sec.

• A. 19.26

Answer 1

The correct option is A 19.26
The tracer records the actual velocity of water

$V_a=\frac{42}{6\times 3600}=1.944\times {10}^{-3}m/s$

$=1.944mm/sec$

Discharge velocity,
$V=n{V}_a[n=0.2]$

$=0.2\times 1.944$

= 0.389 mm/sec

Hydraulic gradient,
$i=\frac{0.85}{42}=0.0202$

$\Rightarrow V=ki$

$\Rightarrow$ Coefficient of permeability,
$k=\frac{0.389}{0.0202}=19.26mm/sec$