Normative Flow Studies Small Streams Biology-Hydrology Analyses



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tarix09.10.2018
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Normative Flow Studies

  • Small Streams Biology-Hydrology Analyses


Project Goals

  • Analytical and decision tools for managers

    • Understand relationships:
    • flows ecological condition
    • Evaluate effects:
    • management actions  flows ecology




Several Possible Approaches….

  • Indicator-based approach – inform management

    • Conceptual Model




Linking Biology and Hydrology

  • Watersheds with both data types

  • Pair biology and hydrology

    • “Subbasins “
    • Distinct hydrology
    • One or more BIBI sites
  • Small data set



Available Data: Hydrology

  • Few long term gauge records

  • Modeled flow data (HSPF) available for some watersheds

  • Developed flow for 50 years

  • Computed metrics for both conditions

    • M, D, F, T, rates of change


Available Data: Biology

  • Macroinvertebrate data

    • Raw data for Benthic Index of Biotic Integrity (BIBI)
      • BIBI - general indicator of ecosystem integrity
      • Not designed to assess effects of flow
      • Only “calibrated” for 2nd and 4th order streams
      • No long term records (1995-2001 longest period)
    • Tested BIBI metrics plus other life history/richness metrics




Working Biological Data Set

  • Issaquah (8/35;34)

  • Bear/Evans (19/63;51)

  • Little Bear (5/18)











BIBI Score vs. Q2:Q10 in sites with similar local land cover (within 100m of BIBI site)





Uni+semi voltine taxa groups





Length of High Pulse Period vs. BIBI Groups



Time (in days) Between Low Pulse Events vs. BIBI Groups



Number of Low Pulse Events/Yr vs. BIBI Groups



Ratio of current 2-yr discharge to historic 10-yr discharge vs. BIBI groups



Potential Hydrology Indicators

  • Stream Power

  • Q2:Q10

  • LP/HP counts, duration, range

  • Onset fall flows

  • % time above 2-yr baseflow



Conclusions



Relationships between biology and hydrology metrics

  • ‘Worst’ and ‘best’ biological sites can be separated based on hydrology metrics

  • Life history and richness metrics significantly correlated with specific hydrology metrics

  • Measures of hydrologic ‘disturbance’ and biological resistance/resilience to disturbance may be most productive



Next Steps

  • Document analyses/report

  • Validate relationships with separate data set(s)

  • Test relationships with other biological data (e.g., fish)

  • Summarize findings for managers – what general guidance can be derived from preliminary analyses?



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