The proposed model allows estimating polymer membrane transport properties. It is based on a microscopic description of charge and water transport in a single capillary with a uniform distribution of charge at the wall. The equations are solved analytically for two geometries: cylindrical capillary and parallel plates. Macroscopic transport properties of the whole membrane are then deduced by upscaling the capillary model. Their variations with temperature and water content are evaluated and compared to data available in the literature. In addition, the influence of the pore size and of the effective charge density are studied. (C) 2008 The Electrochemical Society.