Hydrologic impacts of cascade dams in a small headwater watershed under climate variability

•We developed a framework that integrates SWAT and IHA.•Dams significantly regulate water in small flood events.•Dams reduce streamflow by enhancing evapotranspiration.•Dams could cushion the pulses in wet years and fragment the pulse in dry years.•Dams may amplify the effects of climate variability. Cascade damming poses a threat to watershed health; however, little is known about the hydrologic impacts of cascade dams in the context of simultaneous disturbance from climate variability. A comparison modeling approach that integrates Soil and Water Assessment Tool (SWAT) and Indicators of Hydrologic Alteration (IHA) was proposed in this study to evaluate the hydrologic impacts of cascade dams under climate variability in a small headwater watershed in Southeast China. The results showed that the verified SWAT with the reservoir module had higher Nash-Sutcliffe Efficiency values than those derived without the reservoir module. Cascade dams significantly regulated water in small flood events and reduced streamflow by enhancing evapotranspiration. Climate variability influenced the dam operation on streamflow regime. It was found that dams might cushion the pulses in wet years or fragment the pulses in dry years. Dams amplified the effects of climate variability, represented by increasing baseflow index in wet years. This research demonstrated that the comparison modeling approach proposed could provide useful insights into the hydrologic impacts of cascade dams under climate variability.