Model Water Flow in Rivers

Preparing Your River Model

1. With a permanent marker draw a line on the bottom of the pan about 2 inches into the pan from one of the short ends.
2. With the help of an adult, use the nail to poke a couple of small holes into the bottom of the pan behind the marked line (Figure 3).

Figure 3. Holes at the bottom of the aluminum pan will help drain the water.

3. Add 400 mL of water to one of the plastic cups and mark the water level with a permanent marker inside the cup.
4. Remove the water from the cup. Then, with the help of an adult, use the nail to poke a small hole into the side of the plastic cup, about one inch from the bottom as shown in Figure 4.

Figure 4. Water will flow out through a hole in the cup.

5. Fold three different river channels out of the aluminum foil. Each river should be about 2 inches wide. Make one river channel straight, one a bit curvy, and one very curvy. Some examples are shown in Figure 5.

Figure 5. Examples of several river models.

6. Make sure that all the river models fit inside the aluminum pan. They should start at the far end of the pan and end at the line that you marked inside the aluminum pan.

Measuring Water Flow Depending on the River Shape

1. Find a space outside where you can set up your river experiment. It should be a place where the water from the pan can drain directly onto the floor or the grass, etc. Note: If you cannot go outside place a water collection container such as a small bowl or a tray underneath the end of the aluminum pan that has the holes in it.
2. In your lab notebook, make a table similar to Table 1. Write the names of the three river shapes that you made into the first column. You could, for example, name them "straight", "slightly curved" and "very curvy".

3. Put the first river model into the aluminum pan, so that it ends at the marked line and starts at the opposite side as shown in Figure 6. Secure the river model in place with tape.

Figure 6. The river model ends at the marked line starts on the opposite side of the aluminum pan.

4. Once the river model is placed into the pan, smooth out the aluminum riverbed, so that it is as flat as possible. This is very important as you want to avoid that water pooling behind a foil wrinkle instead of flowing down the river.
5. Before you start with the water flow, measure the length of the aluminum channel with a piece of string. Do this by placing a string in the middle of the riverbed as shown in Figure 7. Cut the string where the aluminum channel ends. Mark the string, so you know which river shape it belongs to.

Figure 7. A string is used to measure the length of the river.

6. Place the top end of the aluminum pan on a book that is about 1 inch high to create a slope for the river. The end with holes should be at the bottom. Note: If you use a collection container, make sure that the top end of the aluminum pan is 1 inch higher than the bottom end with the water collection container.
7. Fill the cup with water up to the mark. Cover the little hole with one of your fingers, so the water does not flow out. Optionally, you can add food dye to the water, to see the water better.
8. Position the cup at the top of the aluminum pan, so that the hole lines up with the river channel. The final experiment setup is shown in Figure 8. If necessary, place your cup on the second cup or a box to make it the right height.

Figure 8. Experimental setup for testing the water flow in the different river models. Note: This setup does not show a water collection container.

9. Have your stopwatch ready. Then remove your finger from the hole. As soon as the water starts flowing into your river channel, start your stopwatch. Note: If the water from the cup does not flow into the river channel, reposition the cup until it does. Then fill it up to the mark with water again and let the water drain from the aluminum river before starting again.
10. Observe how the water flows along the river and stop the stopwatch as soon as it reaches the marked line at the end of the river channel. Write down the time it took for the water to travel down the river into your data table. Round your time to the nearest second.
11. Remove any remaining water from your river model by turning the pan upside down and tapping it gently. You can also use a paper towel to carefully dry the inside of the aluminum channel. Then reposition the pan on the 1-inch book as you did before.
12. Refill the cup to the marked level with water and cover the hole with your finger.
13. Repeat steps 8–12 two more times. Each time write your measured time in the data table. Dry out the aluminum pan in between each trial, but make sure not to change the position of your river model inside the pan. Scientists repeat every measurement several times to confirm their results.
14. Once you are done with your first river model, remove it from the pan, dry the pan out with paper towels and repeat steps 3–13 with the other two river models. Make sure to write each of your measured times into the data table. Make sure to smooth out the aluminum riverbed for all river models before you start your measurements.

Analyzing your Data

1. Look at your data in Table 1. Did you get the same measurements for each trial? How different or similar are your measurements for each trial? If the measurements are all very similar, you know that your data is correct. If they are very different from each other, then something must be wrong with your measurements or your test setup.
2. Making graphs may help you visualize your data. If you need help creating graphs, try the Create a Graph website.
3. Based on your results in Table 1, make a single bar graph for each river shape. Graph the three measurements (or trials) you did for one river shape on the horizontal axis and the time it took for the water to flow down then river for each trial on the vertical axis. You can also write the measured values above the bar for each trial. Do not forget to label the axes and add a title. An example showing how to graph your data is shown in Figure 9. Here is a a graph template to use.

Figure 9. An example bar graph showing all three water flow measurements for the river model that was slightly curved.

4. Take all three strings that you cut for each river shape and place them next to each other. Which river is the longest? Which one the shortest? Can you explain why?
5. Look at the graphs and the strings for all three river shapes. Can you observe a trend? How does the shape of the river affect its water flow? Can you explain your results?
6. Based on your results can you make a general statement about how the water flow in a river is affected by its shape? Such a statement could be:
   • In a very curvy/slightly curved/straight river, water takes ____________________ [fill in blank] to travel down the river because _________________________________________ [fill in blank].