31 Jan 2022
31 Jan 2022
Status: this preprint is currently under review for the journal HESS.

Recession discharge from compartmentalized bedrock hillslopes

Clément Roques1,2, David E. Rupp3, Jean-Raynald de Dreuzy1, Laurent Longuevergne1, Elisabeth R. Jachens4, Gordon Grant5, Luc Aquilina1, and John S. Selker4 Clément Roques et al.
  • 1Univ Rennes 1, CNRS, Géosciences Rennes - UMR 6118, F-35000 Rennes, France
  • 2Centre for Hydrology and Geothermics (CHYN), Université de Neuchâtel, Neuchâtel, Switzerland
  • 3Oregon Climate Change Research Institute, College of Earth, Ocean, and Atmospheric Sciences, Oregon State University, Corvallis, OR, USA
  • 4Biological and Ecological Engineering Department, Oregon State University, Corvallis, OR, USA
  • 5Pacific Northwest Research Station, Forest Service, U.S. Department of Agriculture, Corvallis, Oregon, USA

Abstract. We used numerical modelling to explore the role of vertical compartmentalization of hillslopes on groundwater flow and recession discharge. We found that when hydraulic properties are vertically compartmentalized, streamflow recession behaviour may strongly deviate from what is predicted by groundwater theory that considers the drainage of shallow reservoirs with homogeneous properties. We further identified the hillslope configurations for which the homogeneous theory derived from the Boussinesq solution approximately hold and conversely for which it fails. By comparing the modelled recession discharge and the groundwater table dynamics, we identified the critical hydrogeological conditions responsible for the emergence of strong deviations. The three main controls are i) the contribution of a deep aquifer connected to the stream, ii) the heterogeneity in hydraulic properties, and iii) the slope of the interface between shallow permeable compartment and deep bedrock one with lower hydraulic properties. Our results confirm that a physical interpretation of the recession discharge exponent b from the classical equation −dQ / dt = aQb, and its temporal progression, are information that can only be interpreted with knowledge on structural configuration and heterogeneity of the aquifer.

Clément Roques et al.

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Clément Roques et al.

Data sets

Model results presented in HESS-2022-7, HydroShare Clément Roques

Clément Roques et al.


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Short summary
Streamflow dynamics is directly dependent on contribution from groundwater, with hillslope heterogeneity being a major driver in controlling both spatial and temporal variabilities of recession discharge behaviors. By analyzing new model results, this paper identifies major structural features of aquifers driving streamflow dynamics. It provides important guidance to inform catchment to regional scale models with key geological knowledge influencing groundwater – surface water interactions.