In this topic you will learn how humans use fresh water.

There is only a small amount of fresh water available for human use. Out of all of Earth's water supply, only 3/100 is fresh water. Out of that fresh water supply, only 1/10 is easily obtained for human use.

Every day people use water at school, at home, in stores, offices, and restaurants. A person needs only a few quarts of water a day to stay alive. In the United States, each person may use as much as 200 gallons a day. The water is used for personal and household uses. Some uses include drinking, cooking, cleaning, flushing toilets, and watering gardens.

Farms use water, too. In places where rainfall is low or irregular, water for growing crops is supplied by irrigation. Irrigation is a way to get water into the soil by artificial means. It is used to help increase crop production.

Wastes from industry, farming, and humans are sources of water pollution. Rivers and lakes become polluted when untreated wastes are dumped into them. The place where water is made clean and pure is called a water treatment plant. At the plant, water passes through a screen to remove animals, plants, and trash. Chemicals are mixed with the water to remove impurities and kill harmful bacteria. Water then moves to a settling basin where most impurities sink. Any impurities that are left are removed by filtration. Filtration is the passing of a liquid through materials that remove impurities. Finally, chlorine is added to kill any remaining bacteria.

Most of the water used in homes and factories is used to carry off waste. Water mixed with waste is sewage. Sewers are large pipes or channels that carry sewage to a sewage treatment plant where sewage is treated before it is returned to rivers and lakes. Areas with no public sewage systems have septic tanks. A septic tank is an underground tank in which sewage is broken down by bacteria.

We can save water. The use of water-saving methods is called water conservation. It helps reduce the amount of water needed. Since only a small part of Earth's water supply is fresh water, it is important to save and use water wisely.