I always assign this project towards the end of my unit on the water cycle. I give the students about a week or two to complete it at home for a project grade. The project is to be 3-d and done in a box. They are not aloud to turn in any drawings. They are told to use recycled things from around the house. I tell them to look in the junk drawer etc.. They can use things like plastic or paper grocery bags, cotton balls, yarn, beads, sponges etc.. They must label the project with the correct parts of the water cycle. They must show evaporation, condensation, precipitation, saturation, ground water, surface run-off. The project counts as 25% of their grade. The results are amazing. Have fun!