Spatial patterns of hyporheic exchange and biogeochemical cycling around cross-vane restoration structures: Implications for stream restoration design

Ryan P. Gordon, Laura K. Lautz, Timothy L. Daniluk

Research output: Contribution to journalArticle

49 Scopus citations

Abstract

Natural channel design restoration projects in streams often include the construction of cross-vanes, which are stone, dam-like structures that span the active channel. Vertical hyporheic exchange flux (HEF) and redox-sensitive solutes were measured in the streambed around four cross-vanes with different morphologies. Observed patterns of HEF and redox conditions are not dominated by a single, downstream-directed hyporheic flow cell beneath cross-vanes. Instead, spatial patterns of moderate (<0.4 m d-1) upwelling and downwelling are distributed in smaller cells around pool and riffle bed forms upstream and downstream of structures. Patterns of biogeochemical cycling are controlled by dissolved oxygen concentrations and resulting redox conditions, and are also oriented around secondary bed forms. Strong downwelling into the hyporheic zone (0.5-3.5 m d-1) was observed immediately upstream of structures, but was limited to an area 1-2 m from the cross-vane; these hyporheic flow paths likely rejoin the stream at the base of cross-vanes after residence times too short to alter nitrate concentrations or accumulate reaction products. Total hyporheic exchange volumes are ∼0.4% of stream discharge in restored reaches of 45-55 m. Results show that shallow hyporheic flow and associated biogeochemical cycling near cross-vanes is primarily controlled by secondary bed forms created or augmented by the cross-vane, rather than by the cross-vane itself. This study suggests that cross-vane restoration structures benefit the stream ecosystem by creating heterogeneous patches of varying HEF and redox conditions in the hyporheic zone, rather than by processing large amounts of nutrients to alter in-stream water chemistry.

Original languageEnglish (US)
Pages (from-to)2040-2055
Number of pages16
JournalWater Resources Research
Volume49
Issue number4
DOIs
StatePublished - 2013

Keywords

  • groundwater-surface water interaction
  • heat tracing
  • hyporheic zone
  • nitrate
  • redox biogeochemistry
  • stream restoration

ASJC Scopus subject areas

  • Water Science and Technology

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