Individual water use has increased dramatically in the recent past. People in Imperial Rome used about 144 liters (38 gallons) a day, and the use in London in 1912 was only 151 liters (40 gallons) per person. Just before World War II, typical daily use in American cities was up to about 435 liters (115 gallons). By the mid-1970s, Los Angeles inhabitants were using 689 liters (182 gallons) per person each day.
Our current practices use large amounts of high-quality water for low-grade tasks like flushing toilets. Better conservation practices reserve high-quality water for high-quality tasks like drinking and preparing food, reduce overall use, and recycle water for lower quality uses.
The increasing population and consumption per person puts pressures on the limited supply of clean water, threatening world health and political stability. When people upstream use more than their share of water, people downstream suffer. Agriculture and industry use very large quantities of water. Building and landscape designs often disregard water conservation to make an impression through water use. Extravagant watering of golf courses and swimming pools in desert areas flaunt an affluent lifestyle at the expense of other priorities. Water pumped out of coastal areas pulls saltwater into freshwater aquifers.
As the world's water use rose from about 10 to 50 percent of the available annual water supply between 1950 and 1980, available potable water declined rapidly. Potable water is water that is free of harmful bacteria and safe to drink or use for food preparation. The water carried from the public water supply to individual buildings in water mains—large underground pipes—must be potable.
Protecting and conserving our clean water supplies is critical to our health. Until recently, a reliable supply of clean water was not always available, and epidemic diseases continue to be spread through unsanitary water supplies. Water from ponds or streams in built-up areas is unsafe to drink, as it may contain biological or chemical pollution.
Bacteria were unknown to science until discovered in Germany in 1892. In 1817, thousands of people in India died from cholera. The epidemic spread to New
York City by 1832, causing panic. A breakthrough came in 1854, when a London physician showed that local cases could be traced to one water pump that had been contaminated by sewage from a nearby house. Cholera remains a great danger today, with an epidemic originating in Indonesia in 1961 traveling slowly around the world to reach Latin America in 1991.
In 1939, typhoid carried through the water supply killed 30 people at an Illinois mental hospital. Typhus and enteritis sickened people in Rochester, New York, when polluted river water was accidentally pumped into supply mains in 1940. As recently as 1993, crypto-sporidiosis microorganisms in a poorly maintained public water supply in Milwaukee, Wisconsin, killed 104 people and made 400,000 people ill.
Proper collection, treatment, and distribution of water protect our supplies. Rainwater has almost no bacteria, and only small amounts of minerals and gases. Many communities collect clean water from rain running down mountainsides into valleys in reservoirs. They limit human access to these areas to avoid contamination. Large aqueduct pipes carry the water from the reservoir to communities, usually by gravity flow. Communities without access to relatively uninhabited mountain areas make do with water of less purity from rivers, or tap underground water flows with wells.
The availability of clean water determines where homes and businesses are located, and how many people can live in or visit an area. Water from wells and mountain reservoirs needs relatively little treatment. River water is sent through sand filters and settling basins, where particles are removed. Additional chemical treatment precipitates iron and lead compounds. Special filters are used for hydrogen sulfide, radon, and other dissolved gases. Finally, chlorine dissolved in water kills harmful microorganisms. The result is an increased supply of clean water to support the development of residential and commercial construction.
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