Question

When 3.5 million ${\text{m}}^3$ of water is pumped out from an unconfined aquifer of $6.3{\text{km}}^2$ areal extent, the water table was observed to go down by 2.5 m. The specific yield of the aquifer is best approximated as

• A. 32%
• B. 28%
• C. 25%
• D. 22%

Answer 1

The correct option is D 22%

By considering volumetric approach,

$\text{Water pumped}=S_y\times \text{Area}\times \text{drawdown}$

$S_y=\frac{\text{water pumpdown}}{\text{area}\times \text{drawdown}}$

$=\frac{3.5\times {10}^6}{6.3\times {10}^6\times 2.5}$

$=0.2222\simeq 22\text{\%}$