Climatic signatures in regulated flow regimes across the Central and Eastern United States

Study region: 42 catchments distributed throughout Central and Eastern U.S. Study focus: Enhanced hydroclimatic variability threatens human water uses, and there is an urgent need to quantify projected alterations of flow regimes. This issue has been largely addressed in unregulated rivers through the development of similarity frameworks relating climate properties with the hydrologic response of catchments. However, the impact of damming on climate signatures of river flow regimes is largely unexplored. To fill this gap, this study investigates unregulated streamflows of a selection of sites using a climate-based similarity framework. Then, the corresponding regulated regimes are analyzed to understand how the obtained regime classification is affected by regulation. New hydrological insights for the region: Our results reveal that flood control dams retain but dampen climate signatures of flow regimes, reducing the regional heterogeneity of downstream hydrographs. Conversely, in the study area, urban water supply structures promote climate-independence of river regimes and tend to break the link between climate and river flows, thereby promoting the spatial diversification of the hydrologic response. The observed impact of each specific water use is explained based on quantitative indexes that relates to the regulation capacity of reservoirs and their degree of exploitation. Overall, climatic signatures are still detectable in most regulated streamflows, though climatic control on river regimes is largely concealed by the profound hydrological alterations induced by dams.