Where does streamwater come from in low-relief forested watersheds? A dual-isotope approach

J. Klaus*, J. J. McDonnell, C. R. Jackson, E. Du, N. A. Griffiths

*Corresponding author for this work

Research output: Contribution to journalArticle

36 Citations (Scopus)
3 Downloads (Pure)

Abstract

The time and geographic sources of streamwater in low-relief watersheds are poorly understood. This is partly due to the difficult combination of low runoff coefficients and often damped streamwater isotopic signals precluding traditional hydrograph separation and convolution integral approaches. Here we present a dual-isotope approach involving O-18 and H-2 of water in a low-angle forested watershed to determine streamwater source components and then build a conceptual model of streamflow generation. We focus on three headwater lowland sub-catchments draining the Savannah River Site in South Carolina, USA. Our results for a 3-year sampling period show that the slopes of the meteoric water lines/evaporation water lines (MWLs/EWLs) of the catchment water sources can be used to extract information on runoff sources in ways not considered before. Our dual-isotope approach was able to identify unique hillslope, riparian and deep groundwater, and streamflow compositions. The streams showed strong evaporative enrichment compared to the local meteoric water line (delta H-2 = 7.15 center dot delta O-18 + 9.28 parts per thousand) with slopes of 2.52, 2.84, and 2.86. Based on the unique and unambiguous slopes of the EWLs of the different water cycle components and the isotopic time series of the individual components, we were able to show how the riparian zone controls baseflow in this system and how the riparian zone "resets" the stable isotope composition of the observed streams in our low-angle, forested watersheds. Although this approach is limited in terms of quantifying mixing percentages between different end-members, our dual-isotope approach enabled the extraction of hydrologically useful information in a region with little change in individual isotope time series.

Original languageEnglish
Pages (from-to)125-135
Number of pages11
JournalHydrology and Earth System Sciences
Volume19
Issue number1
DOIs
Publication statusPublished - 8 Jan 2015

Keywords

  • CAROLINA COASTAL-PLAIN
  • RUNOFF GENERATION
  • SURFACE-WATER
  • STORM RUNOFF
  • HEADWATER CATCHMENT
  • CANADIAN SHIELD
  • RIPARIAN ZONES
  • STABLE-ISOTOPE
  • BOREAL PLAIN
  • FRESH-WATER

ASJC Scopus subject areas

  • Earth and Planetary Sciences(all)
  • Environmental Science(all)

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