Fourth graders at Trevvett Elementary have been learning how to make graphs in Math (SOL4.14), and they have been studying the major rivers of Virginia in Social Studies (VS.2). Today, students in Ms. Catlett’s class predicted and graphed the lengths and discharge rates of the rivers. First we located the rivers on Google Maps. I created the map with different layers so that you can click the check boxes on the side of the map to turn on/off the rivers and/or the Virginia border as you discuss each one. We looked at the map scale at the bottom to try to predict the lengths of each river. If you wanted to show your students the watershed for each river (Science SOL4.9a), a great research tool is Streamer. Click the “Trace Upstream” button at the top, then click on a river, and the entire watershed will show up in red. I was amazed at how big the Potomac watershed was and how far it reached into Virginia! After discussing the lengths of the rivers, we tried to predict the discharge. Discharge is the volume of water flowing out the end of the river, measured in cubic feet per second (cu.ft./s). A cubic foot is about 7.5 gallons. We estimated the discharge rate of each river, taking into account their total length, watershed area, and size of the mouth (where it empties into the bay or ocean). Many students automatically assumed that longer rivers would have greater discharge rates, so I asked them a question to help clarify this misunderstanding. Does a longer hose have more water coming out the end than a shorter hose? What does affect how much water flows out the end of the hose? (Water volume, speed and the width of the hose). Does the discharge rate stay the same for each river, like its length? What would make the discharge rate change? (Amount of rainfall). Students recorded their predictions on this spreadsheet. Then they did some research to find the answers. Wikipedia has the information as well as simply asking Google, “What is the length/discharge of the ___ River?” The students entered the correct data into their spreadsheet and compared it to their predictions. Finally, I showed them how to highlight the data and graph it. The graph makes it very easy to see relationships between the rivers. You can see a few student examples here and in the screenshot above.
