Sediment Sample Design for a Small Mountain Stream

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Sediment Sample Design for a Small Mountain Stream

• by Gerald Rockwell
• Carnelian Bay, CA Field Office

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Sample DesignExample

• Mountain Stream
• Need to know average annual suspended sediment
  concentrationor
• Annual sediment load.

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General Cr. 2006 HydrographMean daily discharge
30-50 of the load can come from one storm
Where do you concentrate your sample budget?
99of load will come between Dec. and May.
Quarterly samples will not give you a very useful
number. Weekly samples are a waste of resources.
Take the same 52 samples and target the periods
of higher discharge. This will provide all the
information needed to calculate annual load or
concentration.
Conc. 0-1 mg/l, 0 load
Conc. 0-1 mg/l, 0 load
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December 31, 2005 Peak
How do you sample an unusual peak?
This will give you a reasonable conc. curve to
calc. mean daily conc. or load.
One on the rise And two on the recession
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May 2006 Snowmelt Diurnals
How do you sample a snowmelt cycle?
This will give you an answer biased high.
This will give you an answer biased low.
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May 2006 Snowmelt Diurnals
Sample 2-3 times a week at varying times, plus 1
or 2 diel samples per year.
This will give you the information you need to
calculate an accurate annual load or mean annual
concentration.
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A mature data collection program has the
following

• Standard methods documented
• Written quality assurance plan
• Repeatable, traceable process
• Lots of quality assurance measurements
• Statistical error analysis
• ISO accreditation
• Data published or readily available on the web.
• Data is readily accessible by multiple users