Riparian hydraulic gradient and stream-groundwater exchange dynamics in steep headwater valleys

Thomas Voltz, Michael Gooseff*, Adam S. Ward, Kamini Singha, Michael Fitzgerald, Thorsten Wagener

*Corresponding author for this work

Research output: Contribution to journalArticle (Academic Journal)peer-review

32 Citations (Scopus)

Abstract

Patterns of riparian hydraulic gradients and stream-groundwater exchange in headwater catchments provide the hydrologic context for important ecological processes. Although the controls are relatively well understood, their dynamics during periods of hydrologic change is not. We investigate riparian hydraulic gradients over three different time scales in two steep, forested, headwater catchments in Oregon (WS01 and WS03) to determine the potential controls of reach-scale valley slope and cross-sectional valley geometry. Groundwater and stream stage data collected at high spatial and temporal resolutions over a period encompassing a 1.25 year storm and subsequent seasonal baseflow recession indicate that hydraulic gradients in both riparian aquifers exhibit strong persistence of down-valley dominance. Responses to rainfall do not support the simple conceptual models of increased riparian hydraulic gradient toward streams. Hydraulic gradient response in WS01 to both the seasonal baseflow recession and the storm suggested the potential for increased stream-groundwater exchange, but there was less evidence for this in WS03. Results from four constant-rate tracer injections in each stream showed a high baseline level of exchange overall, and both a slight seasonal increase (WS01) and slight decrease (WS03) in the riparian intrusion of tracer-labeled stream water as stream discharge receded. These results indicate that steep headwater valley floors host extensive stream water exchange and very little change in the water table gradients over 3 orders of magnitude of stream discharge.

Original languageEnglish
Pages (from-to)953-969
Number of pages17
JournalJournal of Geophysical Research: Earth Surface
Volume118
Issue number2
DOIs
Publication statusPublished - Jun 2013

Keywords

  • headwater valleys
  • riparian hydraulic gradients
  • stream-groundwater exchange
  • baseflow recession
  • storm response
  • riparian water tables
  • SUBSURFACE WATER EXCHANGE
  • SURFACE-WATER
  • DISCHARGE
  • ZONES
  • FLOW
  • FLUCTUATIONS
  • CATCHMENTS
  • HYDROLOGY
  • RETENTION
  • TRANSPORT

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