What is Water Pollution?

There's Something In the Water

Water pollution is defined as the introduction of chemical, physical, or biological agents into water. These pollutants are not what we want to see in our water. Watch the video below to see more about water pollution.

Let’s take a deeper look into water pollution.

So What is Water Pollution?

Water pollution is defined as the introduction of chemical, physical, or biological agents into water. Pollutants degrade the quality of water in an ecosystem as well as the health of its living inhabitants.

The two main causes of water pollution are industrialization and rapid increase in human population.

Water pollution happens when contaminants enter bodies of water. Contaminants are any substances that harm the health of the environment or humans. Most contaminants enter the water because of humans. Surface water (river or lake) can be exposed to and contaminated by acid rain, storm water runoff, pesticide runoff, and industrial waste. This water is cleaned somewhat by exposure to sunlight, aeration, and microorganisms in the water. Groundwater (private wells and some public water supplies) generally takes longer to become contaminated, but the natural cleaning process also may take much longer. Groundwater can be contaminated by disease-producing pathogens, careless disposal of hazardous household chemical-containing products, agricultural chemicals, and leaking underground storage tanks.

Causes of Water Pollution

Natural events, like storms, volcanic eruptions and earthquakes can cause major changes in water quality. But human-caused contaminants have a much greater impact on the quality of the water supply. Water is considered polluted either when it does not support a human use, like clean drinking water, or a use for other animals and plants. The overgrowth of algae, known as an algal bloom, can result from the runoff of fertilizer into bodies of water. This excess of nutrients allows the algae to grow beyond control and bring harm to the rest of the ecosystem.

Water pollution can be grouped into two categories:


Results from the contaminants that enter a waterway or water body through a single site. Examples of this include untreated sewage, wastewater from a sewage treatment plant, and leaking underground tanks.	Contamination that does not come from a single point source. Instead, it happens when there is a buildup of small amounts of contaminants that collect from a large area. Examples of this include fertilizer runoff from many farms flowing into groundwater or streams.

Nonpoint source water pollution affects a water body from sources such as polluted runoff from agricultural areas draining into a river, or wind-borne debris blowing out to sea. Nonpoint source pollution can be contrasted with point source pollution, where discharges occur to a body of water or into the atmosphere at a single location.

Let's Recap

Nonpoint source pollution has the largest impact on our water quality because it comes from everywhere. Many choices we make each day can cause nonpoint source pollution.
Small amounts of chemicals that are spilled on the ground stay there until water from rain or snowmelt moves it into our lakes, rivers, and streams.
Nonpoint source pollution is picked up and carried by water when it falls on the land. Water naturally flows down a watershed and drains into rivers, lakes, and streams. Roads, parking lots, and fields are all designed to move water quickly into natural waterways to prevent flooding, but fast-moving water can take even more nonpoint source pollution with it.

3 Main Sources of Water Pollution

Yuck! It's Sewage!

The most widespread source of water contamination in developing countries is raw sewage. In underdeveloped countries raw sewage is dumped into the same water that people drink and bathe in.

People in India sitting in water polluted with raw sewage.

Worldwide approximately 3.2 million children die each year as a result of unsafe drinking water and poor sanitation because access to adequate wastewater treatment facilities in the developing countries is very limited. The reason behind this is the lack of finances to fund the infrastructure needed to help control water pollution.

Watch the video below to review water pollution.

What is Water Pollution? Challenge

Before You Go, You Need To Know

The following key points are from this explore section of the lesson. You must know the following information before moving to the next lesson. This is just a summary of the key points.

Sources of water pollution can be grouped as point source pollution (large amounts entering through a single site) or nonpoint source pollution (small amounts entering from many sites.)
Municipal pollution comes from sewage, storm drains, septic tanks, boats, and runoff from yards.
Industrial pollution, from factories and hospitals, includes radioactive substances; heavy metals and other pollutants in industrial waste; by-products of fossil fuel burning; oil and other petroleum products; and heat from factories and power plants.
Agricultural pollutants include wastes from animals, pesticides, herbicides, fertilizers, and soil.

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