A rheological model of the flow of an aqueous electrolyte solution near a polar interface is presented, which is based on general equations of electrostatics and mechanics of an isotropic inhomogeneous continuum. The main purpose of the theory is to account for the consequences of an additional orientation of water molecules caused by the electrical fields of the double layer. Equations of the rheological model are merged with a modified Poisson‐Boltzmann equation in which hydration effects and dielectric saturation are included. Results of a numerical simulation of the flow of 10−5N KCl solution in capillary slits of varying widths between 104 and 10 nm, with negative surface charge densities assumed to be 6.7, 0.3, and 0.13 μC/cm2, under pressure gradients in the range of 104 to 109 Pa/m, are presented and discussed.