Subtopic: Planning, design and layout of surface and sub-surface drainage systems
Question Statement:
Which of the following assumptions are invoked in Hooghoudt's steady-state subsurface drainage formulation?
Options:
(A) The soil is homogeneous and isotropic with hydraulic conductivity $K$
(B) The Dupuit-Forchheimer assumption of horizontal flow streamlines is valid
(C) Recharge from rainfall or irrigation is uniform and steady across the area
(D) The water table shape between drains is strictly a straight horizontal line
Answer Key:
A, B, C
Step-by-Step Solution & Explanation
Hooghoudt's Drainage Assumptions (ILRI / Ritzema):
- **A is TRUE**: Single homogeneous soil layer with hydraulic conductivity $K$.
- **B is TRUE**: Dupuit-Forchheimer horizontal streamline assumptions.
- **C is TRUE**: Steady, uniform recharge rate $q$.
- **D is FALSE**: The water table forms an elliptical/curved phreatic surface, not a straight horizontal line.
Correct options: **A, B, C**.