Linked from
The 17 pages that link to Pressure gradient, each with the reason it gives.
PressureRelated: Pressure gradients drive fluid acceleration and flow.
Euler equationsRelated: Pressure gradients accelerate fluid when viscosity is absent.
Hagen–Poiseuille equationRelated: The pressure drop along the tube drives the flow.
Darcy's lawBroader topic: Darcy's law makes flow proportional to this driving gradient.
CurrentRelated: Pressure differences can initiate and accelerate fluid flow.
Flows in porous mediaRelated: It is a principal driving force for flow through porous solids.