One activity was adapted from a terrific idea shared with me by Pat Calfee, a former elementary teacher who is now an educational consultant. When Pat was teaching 2nd grade, she used plastic rotisserie chicken containers to have her students create mini water cycles.
Because 5th graders need to know the full water cycle including transpiration and run-off, we modified our mini water cycles slightly. Each team set up their own mini water cycle by adding a rock to represent a mountain, grass for the vegetation, and a small pond made from aluminum foil and filled with water.
On a sunny day, the best way to power up the mini water cycle is to close the container and put it in the sun for several hours. As the water warms up, it evaporates and then condenses on the inside of the plastic lid. The water then "rains" on the environment inside the container and runs off to form little ponds. Unfortunately, the weather called for rain on the day we were doing this (Murphy's law!). So I brought a large lamp from home that gave off a lot of heat, and we put the containers under the lamp. Soon we were observing evaporation, transpiration, condensation, precipitation, and run-off!
Another way to observe a water cycle in action is to create a Cloud in a Jar. This is a teacher demo since it involves boiling water and a lit match, but it's a fun way for students to observe how clouds form. You can find the directions for this activity in my Science File Cabinet on Teaching Resources. The directions include a set of follow-up questions to help students grasp the essential concepts.
What are your favorite activities to teach the water cycle? Please share!