Purpose
To help students comprehend why great rivers don’t run dry—that the water cycle supplies them more-or-less continuously. To help students understand that the river system carries materials in addition to water and that these materials are essential to how rivers and their floodplains look and act.
Context
This lesson was developed by Dr. Penny Firth, a scientist, Dr. Richard Sparks, of the University of Illinois Urbana-Champaign, and Milton Muldrow, Jr., a scientist, as part of a set of interdisciplinary Science NetLinks lessons aimed at improved understanding of environmental phenomena and events. Some of the lessons integrate topics that cross biological, ecological, and physical concepts. Others involve elements of economics, history, anthropology, and art. Each lesson is framed by plain-language background information for the teacher.
This is the first lesson of a three-part series entitled Great Rivers: Where Ecology Meets History. These lessons address the concept of large rivers as dynamic ecological systems that have had vital influences on human history. In Great Rivers 1: The Nature of Great Rivers, students are shown the basics of the water cycle. They are introduced to the concept that flowing water carries materials such as silt, plankton, leaves, and wood. They also learn how rivers and the materials that they carry define how they look and act.
Great Rivers 2: The Ups and Downs of River Flooding focuses on flooding, both because of its importance to human history and because it is often misunderstood. Key to this lesson is the concept that some floods may be predictable in a general way (i.e., in the springtime), but rivers do not flood on a schedule.
Great Rivers 3: Great Rivers, Great Givers consists of a variety of brief sketches that illustrate for students how rivers have influenced human history from the dawn of civilization.
Students should know that water flows downhill. That it follows the lowest possible course and therefore that streams join to become small rivers, which join to become large rivers. The very largest rivers are referred to in these lessons as Great Rivers.
Studies of student thinking show that, at all ages, they tend to interpret phenomena by noting the qualities of separate objects rather than by seeing the interactions between the parts of a system. For rivers, then, students commonly believe that what you find in a river is water. This is certainly partially true. But it is the other stuff in the river that really makes it interesting.
Contact Dr. Firth at pfirth@nsf.gov.
Planning Ahead
You will want to look through the different exercises described below and decide which are feasible for your class.
Motivation
To help get your students motivated for this lesson, ask them: "Are there any rivers near where you live?" Once you have gotten their responses, use a computer with an overhead projector to take them to the U.S. Geological Survey Waterwatch site, where you can show them a map of the United States that shows where we have records of river flow. River flow is the amount of water moving down the river at a given time. Click on your state for a state map, and then on the dot nearest to your school. You will get a graph of the flow at that point in the river. Students will be able to see how the flow in the past week compares with the long-term historical record that the USGS keeps. For some rivers, the record is more than 50 years! The USGS Realtime Water Data site shows a snapshot of the present water flow conditions for the United States. Ask students: "Is your region currently experiencing especially high or low rainfall?"
Development
In this section, students will learn about the hydrologic or water cycle as a system and the important role rivers play in this cycle.
To start, have your students use their Great Rivers 1 student esheet to go to The Nature of Great Rivers where they should read the "Why Don't Rivers Run Dry?" section. Once students have finished with this section, students should use their esheet to go to the Hydrologic Cycle, where they can go through an excellent, animated visual guide to the processes of the hydrologic cycle. Rivers depend on all parts of the cycle. After the students go through the animated water cycle, they should be able to discuss the questions found on the esheet with the class. They can record their answers to these questions on the Nature of Great Rivers student sheet. You can find answers to these questions on the Nature of Great Rivers teacher sheet.
Now students should go on to read the "Why Do Rivers Carry Stuff?" section of The Nature of Great Rivers. Once students have finished going through this section, hold a class discussion about what they've read using the questions on the teacher sheet.
What happens to all the stuff that rivers carry? Where does it come from in the first place? Using their esheet, students should go on to read the "How Do Rivers Make Their Beds?" section. Once they are done, discuss the questions on the teacher sheet.
In addition to reading the student resource, students would benefit from a hands-on examination of what is in a river. If a field trip is possible, have the class collect a bottle of water from your local river or stream. If the whole class cannot go, perhaps you can collect the water and bring it in. Or you can have your students prepare their own "river water" by mixing different combinations of gravel, sand, mud, and water.
When you get in the classroom, have students compare the appearance and smell of the river water to tap water. As students are examining the water, ask them questions like: "Is there anything swimming around in the tap water? In the river water?" Now have students shake up the river water to re-suspend anything it has in it. Have them compare the river water to the tap water again. Let the river water settle overnight. Then ask students: "How has the river water changed? Can you see what has settled out? What does it look like? Are there layers?"
Finally, students should read "How do Humans Influence River Beds?" When they are done, discuss the questions from the teacher sheet.
Assessment
Students should now be familiar with the water cycle and how it supplies large rivers more-or-less continuously so that they do not run dry. They should understand that swift waters tend to pick up and carry materials, while slower waters deposit materials. They should appreciate that these processes of erosion and deposition are what gives the river bed, and the floodplain, their essential characteristics (i.e., rocky, muddy, etc.). Students also should understand that human actions have a great influence on what materials are carried by rivers, as well as where and when they are deposited.
In order to bring this lesson to closure, have your class—working in small teams—develop a set of songs on the theme Hungry Water that would demonstrate an understanding of the water cycle and how rivers are part of a system. Ask students to be as creative as possible in representing what they learned from this lesson. They might develop their own instruments such as sand or gravel shaken in a can, water bottles for gurgling sounds, and a shaken piece of metal for "thunder" to represent the hydrologic cycle. Singing or chanting is, of course, appropriate.
Extensions
In addition to the sites listed as part of this lesson, the EPA Water Sourcebooks site is full of exercises dealing with water quality, wetland functions, and similar topics.
The American Rivers site is focused on river conservation advocacy. It includes discussions of river issues, river campaigns, and links to related sites.
Read More
