Field Study:
Measuring Discharge
Purpose: Determine the volume of water passing a particular point on the river at a particular time.
Materials: yard stick, 25' to 50' plastic measuring tape, clip board, paper, pencil
Procedure:
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Measure the width of the river (from the edge of the water on each side).
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Divide this width by 10
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Walk into the river with the measuring tape and yard stick until you are 1/10 th of the distance across. Take a depth measurement with the yard stick and record it.
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Continue across the river and measure the depth at each 1/10 th segment.
Calculation:
- depth x width = area; and area x average velocity = discharge
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So, for each section of river you can calculate the average depth (the sum of the depths at each edge of the section divided by 2);
- You know the width of every section;
- Multiply the average depth times the width. This gives you the area of that section;
- Add all of the area sections together and you have the total area.
- Multiply that by the average velocity and you have the discharge.
| Section
| Depth (ft)
| Average Depth (ft)
| Width (ft)
| Area (sq ft)
| 0 (edge of stream)
| 0
| X
| X
| X
|
| 1
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| 2
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| 3
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| 4
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| 5
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| 6
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| 7
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| 8
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| 9
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| 10 (edge of stream)
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| 0
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| Total Area:
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Discharge: Total Area _________ (square feet) x Average Velocity _________ feet/sec =
Discharge _________ (cubic feet/sec)