Comprehensive assessment of baseflow responses to long-term meteorological droughts across the United States

Baseflow is a critical component of streamflow, as it maintains flow during meteorological drought. However, our understanding of baseflow response to meteorological droughts is limited. In this study, we presented a flexible approach for detecting precipitation and baseflow droughts and their corresponding recovery. Using this framework, we analyzed data from 358 anthropogenically unaffected catchments to characterize the droughts and recovery properties of baseflow across the United States. Results showed that baseflow droughts were more severe than the precipitation droughts, with duration ranging between 9-104 months. There were delayed responses of baseflow to precipitation droughts, showing longer-lasting effects up to 41 months after the end of precipitation droughts. Our analysis also revealed that baseflow drought is controlled by climate and hydrologic responses of a catchment, whereas baseflow recovery primarily depends on post-drought climate conditions. Furthermore, the aridity index can differentiate the spatial patterns of baseflow responses to precipitation droughts. Decadal changes in baseflow droughts revealed that baseflow droughts have become more severe and prolonged due in part to the rise in temperature highlighting the impacts of climate change on baseflow in the mild temperate zone. Overall, this study provides comprehensive insights into baseflow drought detection and its response to precipitation droughts and underscores the importance of these processes for sustainable water resource management.