Bobula - ABOUT



OBJECTIVE

To calculate stream flow volume and identify various zones of stream velocity.

MATERIALS

❖ Calculator

❖ Data Provided

PROCEDURE

Use the following cross-section map to follow the examples:

[pic]

Step 1:

Calculate each section’s area by multiplying the width by the average depth. Add all section’s areas together to get the total cross-section area of the stream.

Area example: section A = 3 ft x (0 + 1.0 ft) = 1.5 ft2

2

Section B = 3 ft x (1.0 + 1.7 ft) = 4.05 ft2

2

Total Area = Section A + B + C + etc…

Step 2:

For velocity, you would mark off 100 feet with two stakes or buoys. You would then release a small, floating object at the upstream stake and record the time it takes to reach the downstream stake. Surface velocity in feet per second is equal to 100 ft. divided by the time in seconds. Average stream velocity is about 0.8 ft/sec times the surface velocity because water travels faster at the surface than in deeper water.

Velocity example:

Assume the time to reach the downstream stake from the upstream stake was 45 seconds.

100 ft* = 2.2 ft/sec at the surface

45 sec.

2.2 x 0.8* = 1.76 ft/sec avg. velocity

* - Indicates a constant for this equation

Step 3:

To determine flow volume, multiply the total area (from Step 1) by the average velocity given in ft/sec (from Step 2).

Flow Volume example:

Total Area x Flow Velocity = Flow Volume

15 ft2 x 1.76 ft/sec = 26.4 ft3/sec

One cubic foot equals 7.5 gallons; therefore, ft3/sec can be converted to gal/ft3 by multiplying.

26.4 ft3/sec x 7.5 gal/ft3 = 198 gal/sec

There are 86,400 seconds per day. Therefore, flow volume is determined by multiplying the number of gallons/second by the number of seconds per day.

198 x 86,400 = 17,107,200 gallons per day

Use this cross-section map to answer the following questions.

[pic]

Show ALL work. Be sure to use the correct units following the examples given on the previous page. Attach a separate page for work if needed:

1. Calculate the area of each section and then the total area:

2. Calculate the flow velocity:

(assume the time was 55 seconds)

3. Calculate the flow volume:

4. Calculate the gallons per second of flow:

5. Calculate the total number of gallons per day.

CONCLUSION

Type your answers and attach them to this packet.

1. In a stream, does velocity increase or decrease near the banks? Explain.

2. What two factors are used in calculate flow volume?

3. Explain the relationship between flow volume and horizontal location.

4. How are aquatic organism populations affected by flow volume?

5. Why would areas with fast moving currents have less biodiversity than areas with slow

moving or no currents?

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LAB #9 – STREAM FLOW VOLUME

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