Question

Two observation wells penetrating into a confined aquifer are located 1500 m apart in the direction of flow. Heads of 50 m and 25 m are indicated at these two observation wells. If the coefficient of permeability for the aquifer is 30 m/day and its porosity is 0.25, the time of travel of an inert tracer from one well to another is

• A. 75 days
• B. 750 days
• C. 1200 days
• D. 3000 days

Answer 1

The correct option is B 750 days

Let the inert traces travel by a distance 'dx' in time 'dt'

$\therefore$ $V_s=\frac{dx}{dt}=Actualvel.offlow$

$V_s=\frac{v}{n}=\frac{dx}{dt}$

Now, $V=ki$

$\Rightarrow$ $V_S.n=ki$

$\Rightarrow$ $\frac{dx}{dt}.n=ki$

$\Rightarrow$ $\frac{1500}{t}0.25=30\times \frac{(50-25)}{1500}$

$\Rightarrow$ $t=750days$