Section 4: Soil and Water Conservation Engineering
Hydrology
Subtopic: Runoff estimation
Question Statement:
A recharge well of 300 mm diameter is constructed in a confined aquifer of 1000 m² d⁻¹ transmissibility. From the top of impermeable bed, the water level in the well is 50 m and the height of constant water level is 40 m. The constant water level occurs at a distance of 150 m from the center of the well. The possible maximum recharge rate is
Options:
(A) 3.16 m³ min⁻¹
(B) 6.32 m³ min⁻¹
(C) 9.48 m³ min⁻¹
(D) 12.64 m³ min⁻¹
Official Answer Key:
B
Step-by-Step Solution & Explanation
For a recharge (injection) well, the Thiem equation applies with the head reversed (buildup instead of drawdown): Q_r = 2πT(h_w − h₀)/ln(R/r_w), r_w = 0.15 m, R = 150 m, T = 1000 m²/d. Q_r = 2π(1000)(50−40)/ln(150/0.15) = 62,832/6.908 = 9095.8 m³/d = ≈6.32 m³/min.
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