Subtopic: Planning, design and layout of surface and sub-surface drainage systems
Question Statement:
The following data were obtained from an agricultural land requiring a pipe drainage system for groundwater control: Hydraulic conductivity = 8.3 cm h⁻¹, drainable porosity = 5%, reaction factor = 0.31 per day and equivalent depth to the impermeable layer = 2.8 m. The drain spacing computed by the Glover-Dumm formula will be
Options:
(A) 60 m
(B) 190 m
(C) 50 m
(D) 6 m
Official Answer Key:
A
Step-by-Step Solution & Explanation
Glover–Dumm formula: S² = π²Kd/(αf), with K in m/day = 0.083×24 = 1.992 m/day, d = 2.8 m, α = 0.31/day, f = 0.05. S² = π²×1.992×2.8/(0.31×0.05) = 55.06/0.0155 ≈ 3552 → S ≈ 59.6 m ≈ 60 m.
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