Municipal Water Use

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Municipal Water Use

Many people live in municipalities (cities, towns, and villages with services such as water treatment, police, and fire departments). One benefit of living in a municipality is that potable water (water safe to drink) is usually available at any time by turning on the tap. Part of the responsibility of citizens and municipal officials however, is to manage and protect the local water supply.

If municipal water becomes contaminated, the result can be far-reaching and rapid. Bacteria and viruses in water can spread throughout the underground reservoir of water (the aquifer) or throughout the miles of pipelines that carries water to houses in towns and cities. As well, non-living pollutants such as oil, gasoline and sediment can spread contaminate water.

The results of such contamination can be disastrous. In the summer of 2000, the municipal water supply of Walkerton, a town in the Canadian province of Ontario, became contaminated with a certain type of bacteria called Escherichia coli (or E. coli for short). This type of E. coli caused a serious illness in over a thousand people who drank the town water, and killed seven people.

In addition to protecting water for human use, water management also benefits the environment. Polluted water is bad for the many creatures that live in the water and depend on the watercourse in their lives.

Protecting municipal drinking water

People who live in a municipality usually have to pay money to the local government for their water. Municipal drinking water may come from wells, which pump water that is located underneath the ground (groundwater) into an underground reservoir. Groundwater is often free of contaminating chemicals and microorganisms because the contaminants are filtered out of the water as it moves downward into the ground, yet the water still must be tested to ensure the absence of contaminants. Once tested, the water is pumped through pipes that run underneath the streets of the municipality. The pipes lead to houses, fire stations, other offices, swimming pools, and the many other places where water is used.

Some municipal drinking water is obtained from streams, rivers, and lakes. This water is called surface water. Surface water must be treated before it can be used for drinking, because there is a greater chance that harmful chemicals or microorganisms could have washed into surface water. Municipalities that rely on surface water will pump the water from the river or lake to a water treatment plant. The water will be cleaned in a series of steps and tested to ensure that it is safe to drink. The treated water can then be pumped to storage tanks until it is used.

In many municipalities, one of the treatment steps is the addition of a chemical called chlorine. This chemical kills bacteria such as E. coli, and so is an effective and inexpensive way to keep the water free from bacteria. The amount of chlorine that is added to water needs to be monitored, since too much chlorine can create taste and odor problems. Furthermore, excess chlorine can combine with organic material in the water (like rotting leaves) to form a compound called trihalomethane that has been linked to the development of cancer in humans. Some municipalities have installed other means of killing or removing microorganisms. These include the use of ultraviolet (UV) light, which kills microorganisms by breaking apart their genetic material. Another technique is to pass the water through a series of filters (a material that has very tiny holes in it). While the water molecules can pass through these holes, the holes are too small to allow most microorganisms to pass through.

After water is used, the chemicals, sewage, and other contaminants must be removed before the water can be reused or returned to a reservoir. In order to accomplish this, wastewater leaves buildings through sewage pipes that lead to the treatment facility, and the treatment cycle begins again.

New York City Municipal Water

New York City has a population of over seven million people. Another one million people are connected to the drinking water pipelines that supply water throughout the city. Drinking water from lakes and storage containers (reservoirs) journeys to treatment plants through underground pipelines, tunnels cut through hillsides, and channels called aqueducts. From the treatment plants, drinking water makes its way to the huge number of people through a system of pipes that, if put together in a straight line, would stretch nearly 7,000 miles (11,265 kilometers), about the distance from New York City to Tokyo. Sewage and other used water are collected by another system of pipes that is also about 7,000 miles (11,265 kilometers) long. Each day, 14 sewage treatment plants can treat about 1.2 billion gallons of wastewater, enough to fill 2,000 Olympic size swimming pools!

The water quality of the New York City municipal water is the responsibility of the New York Department of Environmental Protection. Over 6,000 people work to make sure that the water is safe to drink.

Other uses of municipal water

Many municipalities provide golf courses, swimming pools, sports fields, gardens and parks for their residents. All of these places require water. Fire fighters need easy access to water, which is provided by a system of pipes that lead to fire hydrants positioned throughout the municipality. The fire fighters hook their hoses up to the high-pressure hydrants to fight fires with water. Many municipalities have cleaning programs, where roads and other surfaces are cleared of dirt and other material that piles up during the winter or a dusty, dry summer. Water is sprayed from vehicles that move slowly along the road, to wash away the accumulated grime.

Safeguarding municipal water

Many municipalities have laws that restrict people from throwing garbage into streams, rivers, and lakes, and to stop the dumping of liquids such as oil and gasoline into the water. Preserving undeveloped areas of riverbanks or lakes also encourages growth of natural vegetation that benefits the water supply. By leaving grass, trees, and other vegetation alongside a stream or river, it makes it more difficult for toxic (poisonous) material to wash into the water. Along with this benefit, the natural stream or river bank often becomes an attractive spot to walk, bike ride, and picnic.

Brian Hoyle, Ph.D.

For More Information


Marek, Lee, and Lynn Brunelle. Soakin' Science. Toronto: Somerville House, 2000.

U.S. Environmental Protection Agency. The Water Sourcebooks: K-12. Washington: USEPA, 2000.


"Drinking Water Kid's Stuff." U.S. Environmental Protection Agency. (accessed on August 27, 2004).

"How Urbanization Affects the Hydrologic System." Water Science for Schools, U.S. Geological Survey (accessed on August 27, 2004).

"Water for People." Water for People. (accessed on August 27 2004).