Question

An unconfined aquifer of porosity 35%, permeability 40 m/day and specific yield of 0.15 has an area of $100{\text{km}}^2$. If the water table falls uniformly throughout the aquifer area by 0.2 m during a drought, the volume of water lost from storage is ________.

• A. $1.5{\text{Mm}}^3$
• B. $3.0{\text{Mm}}^3$
• C. $7.0{\text{Mm}}^3$
• D. $8.0{\text{Mm}}^3$

Answer 1

The correct option is B $3.0{\text{Mm}}^3$

$\text{Volume lost}=S_y\times \text{Drawdown}\times \text{Area}$
$=0.15\times 0.2\times 100\times {10}^6{\text{m}}^3$
$=3\times {10}^6{\text{m}}^3=3{\text{Mm}}^3$