Introduce water to the students by having a glass of water or going to the water fountain. Discuss where the water comes from and how it comes to us to drink. Look at a globe to discover that 70% of the earth is covered in water. Measure out 1 liter of water. Ask Students to estimate how much of the worlds water is drinkable. Take out 30 milliliters to represent the 3% of the world's water that is freshwater. You can add salt to the rest for effect! Talk about the rest of the fresh water. How much is frozen? (about 80%) Put 6ml of the frozen water in an ice cube tray to represent the frozen water. The remaining water in the dish (around 0.6 percent of the total) represents non-frozen freshwater. Ask students if all of the remaining water is available, or is some of it trapped? (4.5 ml of the water is underground) Then discuss what parts of the world's remaining freshwater is drinkable? Using an eyedropper, remove a single drop of water (0.003 ml) from the dish and drop it into someone's hand. This represents clean, fresh surface water (from lakes, streams and accessible resevoirs) which is not polluted or otherwise unavailable for use. This is approximately 0.00003 percent of the total! Compare this to their estimates. Discuss whether there is enough water available for the current population. Discuss water distribution on earth. Discuss what we can do to keep from wasting water.