Darcy’s law describes:

Correct option is A

Darcy’s law:

Where:
· q = water flux
· K = hydraulic conductivity
· dh/dl = hydraulic gradient
Used for saturated flow.
Why other options are wrong
· (b) Evaporation described by Dalton’s law, not Darcy.
· (c) Water retention curve from capillarity equations, not Darcy.
· (d) Osmotic potential follows Van’t Hoff law.