Two sites, one dominated by Anthyllis cytisoides and the other by Retama sphaerocarpa in south-east Spain were instrumented to measure soil matric potential to a soil depth of 1 m and soil water content to 2·75 m depth within shrubs and grass areas. Soil cores and underground surveys were taken to estimate root length and soil texture, ground cover volume was measured and runoff traps were installed to estimate overland flow in grass and shrub areas. The outcome of the results was summarised as a conceptual model to describe the flow of water within patch vegetation, where the main dominating factor of patch vegetation was found to be the function of shrub canopy/root systems. The results illustrated that not only the dynamics of runoff/runon between grass and shrub areas were significant in redistributing rainfall, but also the morphology of shrub species caused significant differences to the accumulation and movement of water in shrub zones. A comparison of growth and flowering times of grass and shrub species showed that soil water availability for each species differs throughout the year. Such an understanding of water movement within patch vegetation of different species shows that sustainable management practices of semi-arid areas must take into account not only natural vegetation patterns, but also the function of each plant type. Copyright © 2011 John Wiley & Sons, Ltd.