Water, Water Everywhere: Available Drinking Water
Overview
This should be used as a teacher demonstration to give students a visual representation of the amount of water available on earth and where it is located.
Water is the most abundant and important substance on Earth. It is essential to life and is a major component of all living things. There are approximately 336,000,000,000,000,000,000 gallons of water on the earth, existing in three states; solid, liquid and gas.
The sources for this water storage are the oceans, icecaps & glaciers, groundwater, fresh-water lakes, inland seas, soil moisture, atmosphere, and rivers. The students will discover the different water ratios in the earth's total water supply.
| TOTAL TIME | 20 minutes |
|---|---|
| SUPPLIES | Eight (8) 1000 ml beakers, Plastic cup, Eyedropper |
Procedure
- Label beaker #1 "oceans" and fill it with 1000 ml of water.
- Label the following beakers: beaker #2 "glaciers & icecaps", beaker #3 "groundwater", beaker #4 "fresh-water lakes", beaker #5 "inland seas", beaker #6 "soil moisture", beaker #7 "atmosphere", and beaker #8 "rivers".
- Inform the students to assume the earth's total water supply has been reduced to 1000 ml as indicated in beaker #1.
- Ask the students how much water must be transferred from beaker #1 into each of the remaining beakers representing the portion of water in each section. Write their estimates on the whiteboard
- Transfer the following amounts of water FROM beaker #1 to each of the remaining beakers.
- Glaciers & icecaps - 21.4 ml
- Groundwater - 6.1 ml
- Fresh-water lakes - 0.09 ml (∼2 drops)
- Inland seas - 0.08 ml (1½ drops)
- Soil moisture - 0.05 ml (one drop)
- Atmosphere - 0.01 ml (0.2 drop)
- Rivers - 0.001 ml (0.02 drop)
Obviously, the last two, atmosphere and river, will be nearly impossible to obtain. So, the inability to add the last drops will help in the student understand how little water is in those two locations.
Discussion
The students will be surprised how little water is found in each of the remaining beakers. The vast majority of water is found in the oceans; approximately 97.2%. The following are the percentages for each water source:
| Water Source | Water volume (cubic miles) | Total Water (%) |
|---|---|---|
| Oceans | 317,000,000 | 97.24 |
| Glaciers & icecaps | 7,000,000 | 2.14 |
| Groundwater | 2,000,000 | 0.61 |
| Fresh-water lakes | 30,000 | 0.009 |
| Inland seas | 25,000 | 0.008 |
| Soil moisture | 16,000 | 0.005 |
| Atmosphere | 3,100 | 0.001 |
| Rivers | 300 | 0.0001 |
| Total water volume | 326,000,000 | 100.0000 |
Despite the overabundance of rain we often receive, the atmosphere contains very little of the earth's total water supply. This demonstration can lead into water conservation awareness and teaching students to think about ways of saving our drinking water. For more info visit EPA Water Sense
Assessment
To determine if students fully understand the location of water on Earth have students work independently or with a partner to come up with a visual representation using classroom art supplies. This activity would make a great formative assessment to gauge student understanding.