As we always know, there's many method to learn about environment. We always can integrate environment education into math, biology, social science, anything. This experiment is one of them:
First we make a simple boat from tree branch or something else (in Indonesia there's a children play to make ship from banana tree stalk, water lily and other water plant. The main idea is to teach local wisdom, traditional game, and how to make children think creative.
And then, look for a small river. For each group, we divide children into : counter and player. Counter will write data while player keep watching the raft in the river, then.
Make a finish line, 10 meter from the start point. Children will drift the raft (don't forget to connect it with a line first, so the raft will not go to the sea :P ) in your instruction. And when the raft reach finish line, they count the distance and the time. Repeat 10 times and do this experiment for 20 meter (so they will learn about the use of statistic)
Make a table and look for its mean (you may add more for modus, etc if you like)
Discuss this topic:
1. Can we find current velocity from this river ?
2. If I want to deliver a thing (letter in a bottle maybe) through this river into someone stand 12 km from here (let assume there's no trouble for that bottle), how long will it takes?
3. If someone poisoning this river, from this point, how long will it takes to reach Jakarta City (example only) - so the children will start looking for a map, calculate with scale and so on...
4. Do you realize that it realy happened (case no 3) ? What thing we must do to minimize water pollution ? Can we stop water pollution ? - so the children will start to argue each other...
5. Make a promise together that we will stop or minimize water pollution from ourselves... :)
Cartoon picture taken from http://www.dkimages.com/discover/previews/840/10097052.JPG