GATE 2021 CE (CE1) – Question 60
A 20 cm diameter well fully penetrates a 30 m confined aquifer. Steady pumping is 40 L/s, drawdown at the well is 4 m and influence radius is 245 m. Find hydraulic conductivity in m/day, rounded to integer.
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Correct answer: 34 to 38
Explanation
Thiem’s confined-aquifer equation is $Q=2\pi Kbs/\ln(R/r_w)$. Here Q=0.04 m³/s, b=30 m, s=4 m and rw=0.1 m. Thus $K=0.04\ln(245/0.1)/(2\pi30\times4)=0.0004140$ m/s, or 35.77 m/day. **Answer: 36 m/day**.