Why water move through a membrane?

Why does water move through a membrane?

because there is a balanced concentration gradient across the membrane of solute and solvent.

Water moves across cell membranes by diffusion, in a process known as osmosis. Osmosis refers specifically to the movement of water across a semipermeable membrane, with the solvent (water, for example) moving from an area of low solute (dissolved material) concentration to an area of high solute concentration