An existing model for the simulation of solvent flux, transmembrane pressure and velocity in spiral-wound modules has been combined with results on the critical flux of spacer filled channels to simulate the colloidal fouling of an RO spiral-wound module leaf. A number of situations were examined where critical flux was absent, was present or was partially exceeded. These results were found to correspond to information obtained from membrane autopsies - that fouling is distributed unevenly over the surface of a membrane leaf. We were further able to show that the total resistance reaches a steady state over time. The model was also used to simulate situations in which feed conditions were controlled to ensure a fixed production rate.