Normative Flow Studies Small Streams Biology-Hydrology Analyses
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09.10.2018
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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
Urbanization
gradient
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
Original
forested land cover - Baseline
Current land cover (1995/1998) - Scenario
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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