Direct Observation of Hillslope Scale StorAge Selection Functions in Experimental Hydrologic Systems: Geomorphologic Structure and Preferential Discharge of Old Water

Minseok Kim, Till H.M. Volkmann, Yadi Wang, Antonio A. Meira Neto, Katarena Matos, Ciaran J. Harman, Peter A. Troch

Research output: Contribution to journalArticlepeer-review

Abstract

Spatially integrated water transport dynamics at the hillslope scale have rarely been observed directly, and underlying physical mechanisms of those dynamics are poorly understood. We present time-variable transit time distributions and StorAge Selection (SAS) functions for a 28 days tracer experiment conducted at the Landscape Evolution Observatory, Biosphere 2, the University of Arizona, AZ, USA. The observed form of the SAS functions is concave, meaning that older water in the hillslope was preferentially discharged than younger water. The concavity is, in part, explained by the relative importance of advective and diffusive water dynamics and by the geomorphologic structure of the hillslopes. A simple numerical examination illustrates that, for straight plan-shaped hillslopes, the saturated zone SAS function is concave when the hillslope Péclet (Pe) number is large (and thus when the advective water dynamics are more pronounced). We also investigated the effect of hillslope planform geometry on the saturated zone SAS function using a model and found that the more convergent the plan shape is, the more concave the SAS function is. A numerical examination indicates that the unsaturated zone SAS function is concave for straight and convergent hillslopes when the soil thickness is uniform. The concavity of those subcomponent SAS functions signifies that the hillslope scale SAS function is concave for straight or convergent plan shape hillslopes when the hillslope Pe number is high.

Original languageEnglish (US)
Article numbere2020WR028959
JournalWater Resources Research
Volume58
Issue number3
DOIs
StatePublished - Mar 2022

Keywords

  • StorAge Selection
  • age
  • experiment
  • hillslope
  • tracer
  • transit time
  • transport

ASJC Scopus subject areas

  • Water Science and Technology

Fingerprint

Dive into the research topics of 'Direct Observation of Hillslope Scale StorAge Selection Functions in Experimental Hydrologic Systems: Geomorphologic Structure and Preferential Discharge of Old Water'. Together they form a unique fingerprint.

Cite this