Plain English Summary

Key Points:
• Diel hydrologic fluctuations create hyporheic flow path lengths and residence times that span orders of magnitude
• Diel hydrologic fluctuations can produce hyporheic flow path residence times and lengths equivalent to those driven by geomorphic features
• Hyporheic flow path residence time and geometry are not directly coupled

Abstract

The relative roles of dynamic hydrologic forcing and geomorphology as controls on the timescales and magnitudes of stream-aquifer exchange and hyporheic flow paths are unknown but required for management of stream corridors. We developed a comprehensive framework relating diel hydrologic fluctuations to hyporheic exchange in the absence of geomorphic complexity. We simulated groundwater flow through an aquifer bounded by a straight stream and hillslope and under time-varying boundary conditions. We found that diel fluctuations can produce hyporheic flow path lengths and residence times that span orders of magnitude. With these results, hyporheic flow path residence times and lengths can be predicted from the timing and magnitude of diel fluctuations and valley slope. Finally, we demonstrated that dynamic hydrologic boundary conditions can produce spatial and temporal scales of hyporheic flow paths equivalent to those driven by many well-studied geomorphic features, indicating that these controls must be considered together in future efforts of upscaling to stream networks.

Citation

Schmadel, N.M., Ward, A.S., Lowry, C.S., and Malzone, J.M. (2016): Hyporheic exchange controlled by dynamic hydrologic boundary conditions. Geophysical Research Letters. DOI: 10.1002/2016GL068286

This Paper/Book acknowledges NSF CZO grant support.