Osmosis is the process where movement of water particles takes place through diffusion from the higher water concentration zone (lower salinity zone) to the lower water concentration zone (higher salinity zone) through a semi-permeable layer.
The movement of water molecules through a semi-permeable layer (e.g. clay layer) separating solutions in which the chemical potentials of the water molecules are unequal; the water moves to the solution with a higher salt concentration creating a pressure gradient over e.g. the clay layer.
Why is osmosis important?
Osmosis can occur due to pressure release from aquifers with a higher salinity, thereby the water quality of the aquifer.