1. Unit E: Fresh and Saltwater System
Topic 1: A World of Water

2. Our Blue Planet
74% of the Earth’s surface is covered by water and 97% of this water is salt water.
All life depends on water. Without water there can be no life on a planet. 60% of our bodies, 84% of an apple, and 98% of a watermelon are all water.
You lose water constantly through sweat, breathing, etc. To replenish your supply you need to drink an average of 2.5 L/day.

3. Major Uses of Water
Direct Uses – Personal use including drinking and washing.
Indirect Uses – Industrial and agricultural uses including irrigation, cooling, solvent, etc. Often leads to the pollution of the water.
Water use by humans breaks down:
73% irrigation for agriculture (indirect)
22% industrial (indirect)
5% personal (direct)

4. Benefits and Costs to Water Use
Benefits include helps create food, jobs, better products, more convenience, and a strong economy.
Costs include starving native plants and animals of water, increasing soil salinity (soil loses moisture and becomes salty), and pollution of water.

5. The Water Cycle
Controls the distribution of water on the Earth. The sun’s energy drives the water cycle.
Processes include evaporation, condensation, precipitation, and runoff of groundwater.

6. Fresh Water
Only 3% of water on Earth is fresh water, and most of that is trapped in glaciers.
Most of the liquid fresh water is in the form of ground water.
Only 0.02% of water is potable – safe for drinking.
Four countries: Brazil, Canada, China, and the U.S. hold 50% of the fresh water on Earth.