What is Watershed?


Pre-visit Activity
Pre-Activity: How Much Water Can We Drink?
 
 
Overview: The earth is covered with water, but how much of it can we drink? Find out with this fun demonstration you can share with your class. 
 
Length: about 20 minutes
 
Background: Approximately 72% of the earth’s surface is covered with water. 97% of the water on the earth is salt water, which is filled with salt and other minerals. Because salt water can cause dehydration, it is not safe for humans to drink. Although the salt can be removed, it is a difficult and expensive process. A little more than 2% of the water on earth is glacier ice at the North and South Poles. This ice is fresh water and could be melted; however, it is too far away from where people live to be usable. Less than 1% of all the water on earth is fresh water we can actually use. It comes from groundwater, rivers, and lakes, and we use it for drinking, transportation, heating and cooling, industry, and many other purposes. The wildlife found in rivers and lakes use this water, too!
 
Materials:      2 liter plastic bottle
Food coloring
Water
3 tablespoons salt
60 ml. corn oil (~2 oz)
Small pipette
 
Instructions:
  1. Put a few drops of food coloring into the 2 liter bottle and fill it just past the neck with water. This will represent all of the water on earth.
  2. Add the salt and explain that this water is not drinkable.
  3. Slowly add the oil. This will represent 3% of fresh water, including glacier ice, groundwater, rivers, and lakes. (Students should be able to see the difference because the water and oil will not mix.)
  4. Fill the pipette with 1 ml of oil. This is water that is available as groundwater, rivers, and lakes. This is the water that is available to us to drink. 
  5. Pose the rhetorical question: should we take care of this water? Students will learn how to take care of it during their field trip to Shangri La.