You can measure stream flow by timing how long it takes a float to travel a certain distance.
The speed at which a river runs is called its flow rate and is usually measured in feet per second. This measurement indicates stream ferocity and aids in calculating the total volume of water moved, called stream flow, when the value is multiplied by a measurement of the river's cross-section. You can calculate flow rate using some simple tools and basic math.
Instructions
1. Locate an area of the river where flow is unobstructed and free of eddies. Use your tape measure to define a section 20 feet long and place marker flags at both ends.
2. Drop the float just upstream from the beginning of the marked area and wait for it to pass the starting flag. Start the stop watch, then stop it when the float passes the ending flag. Record the time in seconds.
3. Divide 20 by the time in seconds. This will give you the velocity in feet per second. As an example, if the float took five seconds to pass through the marked section, the velocity is 4 feet per second.
4. Repeat this procedure three more times at other, unobstructed locations along the river. Select sections of varying apparent speeds to get a more accurate representation of the average flow rate.
5. Average the results of your measurements to get the most accurate flow rate. As an example, if you calculated the four measurements 4, 8, 2 and 10 feet per second, you would add these numbers and divide by four, which will produce an average flow rate of 6 feet per second.
Tags: feet second, flow rate, average flow, average flow rate, stream flow