We present small-angle X-ray scattering (SAXS) studies of the water evaporation process from controlled porosity glass (CPG) coated with a polysaccharide-polyimine copolymers layer. The comparison of SAXS data with power law scattering and the level of scattering intensity for the material from which water is evaporated shows that SAXS is useful in defining a stage of evaporation or its degree. The results show the applicability of the SAXS method regarding the observation of changes in the thickness of the surface polymer layer during water evaporation. The possibility of estimating the polymer transition layer thickness in dried and wetted samples is an additional advantage of the SAXS method employment in the investigation of polymer-porous material systems.