Question

Two observation wells penetrated into a confined aquifer and located 1.5 km apart in the direction of flow, indicate head of 45m and 20 m. If the coefficient of permeability of the aquifer is 30 m/day and porosity is 0.25 the time of travel of an inert tracer from one well to another...... days.

• A. 750
• B. 900
• C. 1120
• D. 430

Answer 1

The correct option is A 750

Hydraulic gradient, $i=\frac{Differenceinhead}{Length}$

$=\frac{45-20}{1500}=\frac{1}{60}$

Discharge velocity, $v=ki=30\times \frac{1}{60}=0.5m/day$

seepage velocity, $V_s=\frac{v}{n}=\frac{0.5}{0.25}=2m/day$

Time of travel of inert tracer from one well to another,

$t=\frac{Distancebetweenwells}{Seepagevelocity}$

$=\frac{1500}{2}$

$t=750days$