What happens to water movement in an isotonic solution?
Isotonic relationship exists when two compartments separated by semipermeable membrane possess identical effective osmolarity of impermeable solutes, typically around 300 milliosmoles per kilogram for mammalian cells corresponding to 0.9 percent sodium chloride or 5 percent dextrose clinically used for infusion. Osmotic pressure pi equals iCRT is identical on both sides, so water chemical potentials equal and thermodynamic driving force zero. Nevertheless molecular agitation does not cease; water molecules continuously cross lipid bilayer by solubility diffusion and through aquaporin-1 channel
Ref: Alberts et al., Molecular Biology of the Cell, Chapter 11: Isotonic Solutions and Dynamic Equilibrium of Water Flux.