Major flood events have the potential to impact water quality. In this study, the effects of the September 2013 South Platte River flood in Colorado were assessed on the urban water cycle and basin-wide scales using time-series water sampling of three source waters (tap water, wastewater treatment facility effluent, and receiving stream) and a longitudinal sampling of the South Platte River and its major tributaries. Samples were analyzed for 52 major and trace elements.