Changing climate increases discharge and attenuates its seasonal distribution in the northeastern United States

• The impacts of scale on discharge magnitude and timing.
• Increases in annual discharge regardless of river regulation or land development.
• Increases in annual discharge consistent with increases in annual precipitation.
• Dry and wet years have become drier and wetter, respectively.

Study regionThe Hubbard Brook Experimental Forest is well-established as a Long-Term Ecological Research (LTER) site for climate change and anthropogenic impacts studies on hydrological processes. It is located at the headwater regions of the Merrimack Watershed, the fourth largest basin in New England, USA. The watershed is mostly forested (67%) with some developed regions (16%).Study focusWe assessed the scale-dependency of streamflow response to climate variation, river regulation, and development for dry, average, and wet years using long-term precipitation and discharge records.New hydrological insights for the regionThe effects of basin scale were limited to discharges with exceedance probability less than 15% and greater than 60% and were expressed as lagged discharge in large sub-basins and earlier discharge in small catchments. Annual discharge responded to increases in annual precipitation but not to river regulation or land development. In general, the temporal trends showed less discharge in dry and greater discharge in wet hydrologic flow classes.