Question Bank • QB_SUB_IDE_0208
MCQ • 1 Mark
Section 5: Irrigation and Drainage Engineering
Subsurface Drainage: Hooghoudt & Steady-State Equations
Subtopic: Hooghoudt spacing for drains on impermeable barrier
Question Statement:
Hooghoudt's steady-state drain spacing equation ($S^2 = \frac{8 K_2 d h + 4 K_1 h^2}{q}$) assumes:
Options:
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(A) Steady-state rainfall/recharge rate $q$ with horizontal and radial flow components accounted by equivalent depth $d$
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(B) Unsteady transient drainage without an impermeable floor
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(C) Zero soil hydraulic conductivity below the drain level
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(D) Infinite drain depth with zero hydraulic head
Step-by-Step Solution & Explanation
Hooghoudt derived steady-state drain spacing assuming steady recharge $q$, two-layered permeability ($K_1, K_2$), and converted radial flow near the drains to equivalent horizontal flow using equivalent depth $d$.
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