Subtopic: Steady and unsteady flow in confined and unconfined aquifers
Question Statement:
Water from a confined aquifer having transmissivity of 1000 m² day⁻¹ is pumped through a fully penetrating well of 300 mm diameter at a rate of 1200 m³ day⁻¹. If the radius of influence is 400 m, the drawdown in the well under steady-state flow condition in meter is ________. [round off to two decimal places] (Take π = 3.14)
Official Answer Key:
1.48 to 1.53
Step-by-Step Solution & Explanation
• Thiem's equation for confined aquifer: Q = 2πT·sw/ln(R/rw) ⟹ sw = Q·ln(R/rw)/(2πT)
• rw = 0.15 m, R = 400 m: ln(400/0.15) = ln(2666.67) = 7.889
• sw = 1200×7.889/(2×3.14×1000) = 9466.3/6280 = 1.507 m
Computed value: 1.51 m (within official range 1.48–1.53)
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