TERMINOLOGY

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TERMINOLOGY

• Macrohabitat water quality and hydrology
• Mesohabitat commonly occurring habitat types
• Critical habitat important to a species even if
  not common
• Microhabitat depth, velocity and cover within
  each mesohabitat

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PHABSIM Study

• Study Planning
• Locate reaches and transects
• Obtain channel profile and microhabitat data
• Develop hydraulic model
• Input suitability rating criteria
• 6. Output suitability available at each flow
  increment of interest

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Hypothetical flow control issue
Flow control
downstream
4
Review physical characteristics
Minor tributary
Flow control
Repeating channel pattern riffle/run/pool
Major tributary
Unique channel condition cobble rapids
downstream
5
Link species/lifestages or guilds to specific
mesohabitats
6
Define overall study area
Flow control
Juvenile and adult feeding and holding
Spawning bar
downstream
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Stratify reaches according to physical,
hydrologic and habitat use characteristics
Flow control
REACH 1
REACH 2
downstream
8
Select study sites representative of each reach
Representative reach study site
Flow control
REACH 1
REACH 2
Critical reach study site
downstream
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Representative Study Site
pool
Sand bar
riffle
run
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Cell Boundaries are located at breaks in habitat
types
pool
riffle
run
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Cell Boundaries (continued)
pool
riffle
run
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One transect is located within each longitudinal
cell
T-5
pool
T-4
riffle
T-3
T-2
T-1
run
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transect T-1 (looking downstream)
headpin
tailpin
Top of bank
Water surface
Toe of bank
Edge of water
Thalweg
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Verticals are located along each transect to
capture key substrate and profile features
headpin
tailpin
Top of bank
Toe of bank
Edge of water
Thalweg
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Verticals and cell boundaries act to divide each
segment into a mosaic of known areas
T-5
pool
T-4
riffle
T-3
T-2
T-1
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Habitat is pixilated into a mosaic of known
dimensions
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Calibration flows are gathered across the flow
range of interest
High flow (WSL only)
mid flow (WSL and velocities)
low flow (WSL and some velocities)
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This permits interpolation and extrapolation of
other flows
1,800 cfs
100 cfs
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Model output Habitat-flow relationships for
each river segment
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Suggested Problem-Solving Process

• Review hydrology time series
• Compare habitat under existing and alternate flow
  scenarios
• Compare project operation under existing and
  alternate flow scenarios
• Assess extent to which all objectives are met
  under each flow scenario
• Evaluate trade-offs
• Re-run alternative scenarios