The 'Dupuit-Forchheimer assumptions' for unconfined aquifer flow include:
Choose the correct answer
Flow is always vertical only
Flow is horizontal; velocity proportional to water table slope dh/dx (not actual angle) — valid for gentle water table gradients
Soil is isotropic and impermeable
No groundwater exists in unconfined aquifer
Correct Answer
B. Flow is horizontal; velocity proportional to water table slope dh/dx (not actual angle) — valid for gentle water table gradients
Why is this the answer?
Dupuit assumptions: (1) Flow is horizontal (streamlines are horizontal in unconfined aquifer); (2) Velocity gradient is proportional to slope of water table dh/dx at that point (not to angle). These simplify to: q = −kh(dh/dx). Valid for mild water table slopes (< 1:10). Breaks down near wells (steep gradients) and at seepage faces. Gives parabolic water table between drains.
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