 This study examined the hydrologic similarity of 280 catchments in the eastern United States using a six-dimensional signature space. The results showed that these catchments could be grouped into nine homogenous clusters based on their hydrologic responses. These clusters were then linked to climate and landscape attributes such as temperature, elevation, slope and vegetative cover. This study provides evidence that hydrologic similarity can be used to identify regions with similar hydrologic processes and thus enables the transferability of information among different catchments. This article was authored by K. Soutz, T. Wagoner, M. Savapalan and others.