The equation governing flow of water in saturated soil is:

Correct option is C

Correct option: (c) Darcy’s equation
Why (c) is correct:
· Darcy’s law specifically describes laminar flow of water through saturated porous media, such as soils.
· It relates water flow rate to:
· Hydraulic gradient
· Hydraulic conductivity of soil
· It is the fundamental equation in soil physics and groundwater hydrology.
Conceptually:
· Flow ∝ hydraulic conductivity × hydraulic gradient
· Applicable only under saturated conditions.
❌ Why other options are incorrect
· (a) Poiseuille’s equation
· Applies to flow in capillary tubes, not porous soil media.
· (b) Bernoulli equation
· Used for energy balance in fluid mechanics, mainly for open or closed conduits, not soil pores.
· (d) Navier–Stokes equation
· A general fluid motion equation, too complex and not directly applied in routine soil-water flow problems.
�� Key Points
· Darcy’s law governs saturated soil water flow.
· Valid under laminar flow conditions.