I need to find out what my students know about dams. Many have seen one and ask them to share their experience and what they remember about them. The class understands that they are in between canyon like walls and are there to block a river. I ask if they know what the lake behind the dam is called. They do not know and are a bit stumped. I explain that the lake is man made and it is actually a reservoir.
I then ask why we built the dams. Surprisingly, I do not have any students that know their exact purpose. They believe it has to do more with erosion and using the water in our houses. I then explain that inside the dam are giant turbines that make electricity. I explain in a drawing how water is pushed through and makes the turbine spin. This energy is then converted to electricity. I then explain that the Colorado River has four dams on it.
The class is ready to turn and talk, so I ask them to talk with their elbow partner about how these dams might effect the river.
You can use any article on animals or plants that are affected by dams. Within an Evan Moor science book, they had two mini articles that were perfect for reading CLOSELY and for describing the impacts of the dam. One article is on the Saltbush and how it overgrew and started to add too much salt to the river. The other article was on a suckerfish that depending on the flooding of the river to spawn and to eat.
Any article on a dam will do, and you can talk about how with a dam, the river does not get the chance to flood and clean itself, problems can occur. It can cause things to over grow and for other organisms it makes it hard for them to survive.
I went ahead and model a couple of the issues using students. I explain if the water is too low it becomes hard to move. I have students move between a row of desk and then have them pretend that this is the river and now they can only move along the right side of desks. This makes it hard for them to move. We then talk about the goodies you eat are not turned up by moving water, and students realize quickly that this would make it hard for a fish to survive.
I then have students turn to their elbow partners again and they need to decide how they might be able to save the river. I then tell them getting rid of the dam is not an option. I walk around and listen. I want to have a few students to call on for when we discuss all together.
When the conversations are wrapping up, I call on those students to give their solutions. Students have some clever ideas, and one group decided that the dam needs to let out more water. I ask how everyone feels about this. As they confirm and discuss other ideas, I only ask questions to keep them thinking.
I then explain what happened and the solution that scientists had. It was to create flooding the way it might have occurred in real life. This way the water from the dam cleans the river and helps the ecosystems that rely on it.