This document describes a method for measuring the flow of water in a river or stream using a float. The key steps are: 1. Measure the average depth and width of the stream cross-section. 2. Float a small object on the surface of the water and time how long it takes to travel a set distance. 3. Use the formula Volume = Length x Width x Depth to calculate the volume of water flowing past that point in one second, where Length is the distance traveled by the float.

1. Measuring Flow of water

2. Cross section of a Water source
• The following image shows a cross section of a
river stream

3. Measuring float
• Float method
Following method is explained in the slide given
next

4. Measuring flow
From figure in previous slide
We need to
• Calculate the average depth of stream
• Calculate the width of stream
• A piece of wooden/cork material
• Select a straighter area of stream/river/canal

5. Measuring flow
After calculating depth and width
• Now float a small rubber piece on river
• With stop watch measure time taken
• This will be the length

6. Measuring Flow
• Now you know length,width and distance
covered
• You know the time taken by floating rubber
• Now use formula for volume
Volume = length x breadth x depth
You can find out how much cubic meter volume
water flows in one second
Detailed image shown in next slide

7. Measuring flow
• Please refer the following figure
Point A and point B in figure is length
You have width
You have depth
You have time taken
from point A to B
Using formula,volume can be calculated

8. • Distance travelled by object from point A to B
will be the distance
• We have time
• Distance/Time = surface velocity
• Average velocity = surface velocity x 0.85
Usually mean of surface velocity factor comes to
0.85

9. • Now you have average velocity
• Now calculate area of cross section
• Types of area
1) Rectangular 2) Trapezoidal

10. Calculating surface areas
• Rectangular area