GATE 2020 CE (CE1) – Question 60
An unconfined homogeneous aquifer of area 3.00 km² initially has water table elevation 102.00 m. Natural recharge of 0.90 million m³ raises it to 103.20 m. Subsequent pumping lowers it to 101.20 m. Find pumped volume (million m³), to two decimals.
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Correct answer: 1.4 to 1.6
Explanation
Specific yield is $S_y=0.90\times10^6/(3\times10^6\cdot1.2)=0.25$. Pumping drawdown is $103.2-101.2=2$ m. Removed volume is $S_yA\Delta h=1.50\times10^6$ m³. **1.50 million m³**.