Chapter 21

Human Actions and Earth’s Waters

21.1 Humans and the Water Supply

Learning Objectives

• Learn how humans use water.


• Discuss how much water is taken up by each water use.


• Explain the difference between consumptive and non-consumptive water uses.


• Discuss three of the most serious issues humans face today, including shortages of fresh
  water, lack of safe drinking water and water pollution.


• Discuss why humans are facing water shortages.


• Discuss how water shortages can lead to disputes and even battles between states and
  countries bordering on the same water source.


• Explain why one fifth of the human population does not have access to safe drinking
  water.


• Describe the relationship between disease and exposure to unsafe drinking water.


• What is the origin of California’s fresh water supply?

Human Uses of Water

All forms of life need water to survive. As humans, we need water to drink or we need to get
it from the foods we eat. We also use water for agriculture, industry, household uses, and
recreation. Water is continually cycled and recycled through the environment.

Some ways that we use water consume a lot of water that then is lost to the ecosystem
and some ways we use water put less demand on our water supplies. Understanding how
water cycles and is replaced is important, especially when we look for ways to use less water.