by Naomi White, Science Teacher, Jefferson High School, LAUSD

STUDENT HANDOUT

Background and Information

Stream flow is an important factor in streams and rivers. It controlsthe type of bottom dwelling and swimming organisms that can live in thestream. Stream flow also affects turbidity and oxygen content. It willaffect the type of bottom on the stream or river.

You will create a stream model to determine what affects stream flow.You will need the following formulas to calculate velocity, gradient, andvolume.Velocity is the speed of the stream; gradient is how steep thestream bed is; and volume is the amount of water that passes a certainsection of stream.

Formulas:

rate of flow (velocity) = distances (m)/time (sec.)

% slope (gradient) = (vertical distance/horizontal distance) x 100

volume = area x time x velocity

Laboratory Procedure:

1. Measuring from the end of the trough, mark off the followinggraduations: 1cm from end, 21cm from end, 71cm from end.
2. Place the 1cm mark on the edge of the table and raise the other endwith a 2cm wood block.
3. Punch two hole near the corner of the milk jug, 1cm from the bottomand 2cm apart. Plug with the dowels or pencils and fill the jug withwater.
4. Set the jug on top of the support and stand above the raised end ofthe trough. Place a pail on the ground below the other end.
5. Remove one dowel. Drop a small leaf into the stream of water comingdown the trough. Start timing the leaf when it passes the 71cm mark; stoptiming when it passes the 21cm mark. Repeat three trials, refilling themilk jug each time.
6. Repeat procedures for two holes.
7. Raise the trough to 4cm and repeat experiment. Then raise to 10cmand again repeat the procedure. Complete all calculations and graph theresults.
8. Refill the jug. Pour of one liter of water and draw a line on thejug to show the water level. Remove one dowel and time how long it takesfor 1 liter of water to drain from the jug. After calculating the area ofthe hole, use the formula to calculate the speed of the water coming out ofthe hole.