The calculation for determining the flow rate of water is Quantity = Velocity x Area. This formula works when determining how much water is flowing through a pipe or stream. Many farmers want to know how much water is being pushed through a stream bed at any given time so the water can be used to create water powered generators or pumps.
Things You'll Need
- Stop watch or time measuring device
- Yard stick or measuring tape
- Small plastic ball
- Rope or string
Determine the velocity of the water. This is done by marking off a 20 foot section of the stream or pipe. Drop the ball at the beginning mark. Using the stop watch, record how many seconds it takes the ball to reach the end mark. Divide 20 by the number of seconds and multiply by 0.7. For example, if it takes 15 seconds for the ball to travel the 20 foot distance, then the calculation would be 20/15x0.7=0.933. Repeat this process at least three times to gain a more accurate measurement.
Measure the area of the stream. Using the same area of stream used in the first step, tie a rope or string from one side of the stream to the other side. Divide the rope into equal sections and mark these sections. Using the measuring stick, determine the depth of the stream at each of the marks.
Calculate the average depth of the stream by adding all the measurements together and dividing by the number of sections measured. A 6 foot stream measured 5 times with depths of 3/4 foot, 1/2 foot, 1 1/2 foot, 1 foot, and 3/4 foot would be calculated as: 3/4+1/2+1 1/2+1+3/4=4 1/2 feet divided by 5 for a total of 0.9. Multiply 0.9 by 6 (the width of the stream) for a total area measurement of 5.4 square feet.
Use the numbers gathered to process the equation. In the examples above, the calculation would look like this: 0.933 x 5.4 = 5.0382 gallons per hour. This is an estimated calculation to show how the formula works.
- Photo Credit Thinkstock/Comstock/Getty Images
How to Calculate Pipe Flow Rates
Piping systems are designed by selecting piping systems and materials that are compatible with the flowing media and selecting the pipe size...
How to Calculate Well Water Flow Rate
Flow rate for any water pipe is calculated in gallons per minute (GPM). Specialized tools accurately measure the flow rate by attaching...
How to Calculate Flow in a Sewer Pipe
The flow of a sewer pipe describes the rate at which liquid is passing from one end of the pipe to the...
How to Calculate the Flow of Water Through a Pipe
Water through a pipe flows when a pump or gravity provides pressure to drive it. This pressure drops between one end of...
How to Calculate the GPM of Water Flowing From a Pipe
The number of gallons that flow through a pipe each minute (GPM) depends on the pressure differential across it. A higher pressure...