Flexible non-perennial streamflow simulation approach reveals structural controls on flow permanence

Non-perennial streamflow supports ecosystem function and water quality in many headwater systems. Furthermore, flow permanence characteristics in non-perennial streams are increasingly used to assess the federal, state, and tribal protection of headwater streams throughout the United States. Methods to characterize streamflow permanence for individual headwater systems have advanced considerably over the last several decades. However, the development of flexible, process-based modeling frameworks (i.e., those that can be transferred to other watersheds with limited modifications to model parameterization) to simulate streamflow permanence is currently lacking. In this study, we formulate a process-based hydrologic model to characterize streamflow permanence in two well-monitored headwater catchments with distinct structural underpinnings on the Cumberland Plateau in Kentucky, USA. Each model is calibrated and verified using discharge data collected at the watershed outlet, flow-state sensor data in ephemeral, intermittent, and perennial reaches, and headwater extent observed from field reconnaissance. We additionally demonstrate the potential for the model to be upscaled to larger watersheds within the Cumberland Plateau ecoregion, which may have utility in applying the model to other physiographic regions throughout the United States. Finally, we present preliminary findings that show how variability of watershed configuration impacts stream expansion and contraction rates and streamflow permanence throughout each catchment.