Over an area of $50\text{ km}^2$, the water table of an unconfined aquifer dropped by $1.80\text{ m}$ during a dry season. If the specific yield of the aquifer is $S_y = 0.20$, the volume of groundwater depleted in million cubic meters ($\text{Mm}^3$) is ________ (answer in integer).
Answer Key:
18
Step-by-Step Solution & Explanation
Depleted groundwater volume $\Delta V$ is given by:
$\Delta V = A \times \Delta h \times S_y$
Given:
• $A = 50\text{ km}^2 = 50 \times 10^6\text{ m}^2$
• $\Delta h = 1.80\text{ m}$
• $S_y = 0.20$
$\Delta V = (50 \times 10^6) \times 1.80 \times 0.20 = 50 \times 0.36 \times 10^6 = 18.0 \times 10^6\text{ m}^3 = 18\text{ Mm}^3$