Hydrology of Small Streams, Data Availability Jon Hortness Hydraulic Engineer USGS, Boise

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Hydrology of Small Streams,Data
AvailabilityJon HortnessHydraulic
EngineerUSGS, Boise
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Instream Flow Studies Where does hydrology fit
in?

• Biology Students
• WUA
• Substrate
• Cover
• HSC

Whos driving the bus???
Mr. Hydrology
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Hydrology is the DRIVER!!!

• You can have all this wonderful habitat, but if
  the fish cant get there to use it or cant use
  it at the right times, its not very useful
• You must understand the hydrology to make good
  decisions

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Discussion Points

• Data needs for making good decisions
• Available data/estimation methods
• Additional data collection

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Data Needs

• Perfect world (if we could have it all!!!)
• 10 years of continuous data above diversions
• Data for tributaries and diversions
• Seepage studies to determine gaining/losing
  reaches
• What we can live with?
• Estimates of streamflow statistics upstream from
  diversions
• Estimates of tributary inflows and diversion
  withdrawals

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Data Needs cont.

• What do we actually have?
• Typically, not much
• A few instantaneous measurements
• Maybe some historic continuous data
• Little, if any, info on gains and losses
• Little, if any, info on diversions

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Available Data

• Continuous-record streamflow data
• Ideally, above diversions (natural flow
  conditions)
• 10 years of data or more for statistical purposes
• Miscellaneous streamflow measurement data
• Instantaneous measurements in the stream
• Instantaneous measurements of diversions
• Varies greatly by location
• Dependent upon previous work

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Available Data cont.

• Upper Salmon River Basin project
• 16 study sites on 10 different streams
• 4 total gages within the area
• 2 that could be used directly
• 1 used as an index station

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Estimation Methods

• Index stations
• Relate instantaneous measurement data to a nearby
  index gaging station to estimate long-term
  streamflow statistics
• Regional regression equations
• Peak-flow equations are fairly common
• Not too helpful for IFIM studies
• Monthly equations (means, exceedances, etc.) are
  not very common
• Exceedances are typically needed for IFIM studies

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Estimation Methods cont.

• Upper Salmon River Basin project
• Some historic instantaneous measurement data
• Not on the right streams or not at the right
  times to make estimates based on index gages
• Monthly exceedance regression equations
  (80-, 50-, and 20-percent) are available
• Developed for USFS in 2001
• Fairly large estimation errors
• Tend to overestimate streamflow statistics

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Estimation Methods cont.

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Estimation Methods cont.

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Additional Data Collection

• Short-term gaging stations
• Get 1 to 3 years of continuous data to compare
  with nearby index gaging station
• Instantaneous measurements
• (tributaries, diversions, etc.)
• Seepage studies, if necessary

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Additional Data Collection Cont.

• Long-term gages
• We are continuing to operate 2 short-term
  gages (upper Valley Creek and upper Salmon River)
• Equation development
• Intense project in a specific area
• Need a good, fairly large, network of streamgages
• Several years of data collection is necessary

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QUESTIONS?