The River Watch Activity Pack

Measuring the velocity of the river

Key objective:

To find out how fast the river is flowing

Equipment needed

• Stopwatch
• Orange peel or cork

Again make this a problem solving exercise.

• Drop a piece of orange peel or a cork in the river and see how long it takes to travel 10 metres. (Orange peel works well because it is easily available, highly visible and floats)
• Record the time and repeat five times to do an average.

From the time taken for the orange peel to travel 10 metres you need to calculate the river speed in metres per second, so just divide the answer in seconds by 10.

• Write down the speed as metres per second.

A river velocity of 1 metre per second is equal to 3.6 km per hour or about 2 miles an hour.

Problems

Most of these will be operator error; that is the children making errors. Common faults are throwing rather than dropping the orange peel. This is again a good opportunity to discuss and resolve these problems.

Why are we doing this?

Use the cross sectional area and the velocity to calculate the discharge of the river (the amount of water flowing through the river), simply multiply the cross sectional area by the velocity and get an answer in cubic metres per second. As we move down the river we expect to find the velocity, cross sectional area and discharge increase from the source to the mouth.