Root zone storage capacity Sr is a significant variable for hydrology and climate studies, as it strongly influences the hydrological behaviour of a catchment. A climate-derived method (water-balance between precipitation and transpiration) was applied for estimating Sr values for 113 catchments in Australia. Various climate, hydrological and vegetation characteristics were compared with Sr, and the relations between them were analyzed. The eucalyptus forests ,evaporation and the seasonal pattern of climate were determined as more important variables. Principal Component Analysis and K-Means clustering method were applied for clustering these catchments, which indicating the co-evolutionary impacts of climate and vegetation on root zone storage capacity.