RECENT ADVANCES IN UNDERSTANDING THE HYDROLOGICAL VARIABILITY OF NON-PERENNIAL STREAMS AND RIVERS WITH IMPLICATIONS FOR MANAGING THESE HEADWATER SYSTEMS (Invited Presentation)

Over half of global rivers and streams are non-perennial, yet these systems are more poorly monitored and characterized than their perennial counterparts. Better understanding the distribution and drivers of non-perennial flow regimes is critical for understanding their hydrologic, biogeochemical, and ecological functions. We describe recent advances in understanding the hydrological variability of non-perennial streams and explore the implications of these findings across sub-daily to decadal temporal scales and from reach to continental spatial scales. An examination of the global distribution of readily available and easily accessible non-perennial streamflow observations provides insights into the many reasons no flow might be reported at monitoring locations, and provides a guide for prioritizing areas for additional measurements. The spatial patterns and drivers of no flow duration, no flow timing, and dry-down dynamics across the U.S., Australia, and Europe are used to discern groupings of locations with similar non-perennial flow regimes. Changes in non-perennial flow dynamics over time are described to elicit emergent patterns in non-perennial flow regimes. We reflect on the implications of these findings for the management of non-perennial headwater streams and ecosystems in the context of continued climatic and landscape change. In addition, we discuss ongoing and future opportunities aimed at further improving our ability to estimate non-perennial streamflow dynamics and to forecast no flow conditions in headwater areas.