BellringerIn what aspect of our society do you think humans use the most freshwater and why?

Water Supply & Demand

Notes

How People Use Water

•Freshwater is a limited resource, and as more people move to cities, more water is required to supply these individuals with water.

•Water is required for household purposes, industry, transportation, agriculture, and recreation.

How People Use Water

•People need water in homes for many uses.

•Many industries use water to cool hot machinery. Power plants and steel mills also use water for cooling.

Water can be used to cool cutting tools, or to

reduce friction.

How People Use Water

•Since ancient times, people have used boats on water to carry people and products.

•In early America, rivers served as natural highways.

How People Use Water

•Farmers need water to grow crops.

•Some places do not receive enough rainfall to properly water their food supplies.

•Irrigation is when water is supplied to areas of land so crops can be grown.

•In the United States,, more water is used for irrigation than any other single purpose.

How People Use Water

•Of course, humans like their free-time. People use water to have fun, such as for boating, swimming, water-guns, water-balloons, skiing, ice-skating, etc.

Conserving Water•Freshwater is a finite resource, when too many

people try to use it at once, there can be shortages in the water supply.

•Conservation is the practice of using less of a resource so that it will not be used up.

•People often use more water than they really need. You can conserve water at home by doing simple things, such as taking shorter showers.

•Think: one minute in the shower = ~18L of water. Therefore 10 minutes = ~180L of water!

Conserving Water

•New water-saving/recycling methods help industries save money an obey environmental laws.

•Some plants build their own cooling pools to cool off the heated water so that it can be used over again.

•For example, in the 1950s it took nearly 227,000L of water to make 1000kg of writing paper. By the 1980s, paper mills only needed half this amount.

Conserving Water

•There are some ways to conserve water in agriculture.

•For example, sprinkler irrigation sprays water on crops. Much of that water is wasted due to evaporation.

•Newer methods use “drip irrigation.” Drip irrigation drips water onto the soil near the plants’ roots. In this method, very little water is wasted.

Fresh Water for the Future

•As the human population continues to increase, so to does its demand for fresh water. New sources must be found to accommodate the increased demand.

•Two possible methods for obtaining fresh water for the future are desalination and melting icebergs.

Fresh Water for the Future

•Desalination is when the salt is removed from marine water to make fresh water.

•There are several ways to desalinate water, unfortunately all of them are still very expensive.

•One method of desalination is called distillation. First the water is boiled. (Remember that water vapor is always fresh). The water vapor that forms is then cooled to produce liquid fresh water.

Fresh Water for the Future

•Another method of desalination includes freezing the water (same principle as boiling it).

•The third process involves passing water at high pressure through a very fine filter to separate the pure water out. This is known as reverse osmosis.

•Despite the energy and machinery costs, some nations in Southwest Asia and the Arabian Peninsula rely solely on these methods.

Fresh Water for the Future

•Icebergs are made up of frozen water (fresh). Melting an iceberg could proved millions of liters of fresh water.

•Tugboats could tow a wrapped iceberg from Antarctica to a coastal region of Africa or South America. As the iceberg melted, it would provide millions of liters of pure water that could be pumped to shore.

•Such plans could create very distinct environmental concerns. Can you name any?