Technical Abstract: Climatic change will have strong impacts on riverine ecosystems and their associated riparian zones. In the southwestern United States, conservation and restoration of riparian habitats has become a priority for resource management agencies and conservation groups, and these areas are biodiversity hot spots within the arid/semi-arid landscape. Given the dependence of human societies on water, these areas are impacted by water resource development, both of ground and surface waters, with the potential for conflict heightened under an increasingly arid climate and a growing human population. Riparian vegetation and landscapes are likely to be most strongly influenced by climate-linked changes in surface and groundwater hydrology. Using the San Pedro River (Arizona, USA) as our primary case study, we review findings from two decades of research on the relationships between riparian vegetation dynamics, climate, geomorphic change, and both surface and subsurface hydrologic processes. The distribution, composition, and productivity of riparian vegetation are dependent on both surface flows and groundwater dynamics. Floods, both as a source of water and as an agent of ecological disturbance, are important for driving riparian vegetation dynamics. While influenced by both floods and groundwater dynamics, riparian vegetation also exerts important feedbacks on these processes, and on entire system response, via evapotranspiration and influences on bank stability and channel dynamics.