Water Pollution: Definition, Types, and Sources

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  • 0:05 What Is Water Pollution?
  • 1:24 Two Sources of Water Pollution
  • 2:26 Surface Water Pollution
  • 4:21 Groundwater Pollution
  • 5:55 Lesson Summary
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Lesson Transcript
Instructor: Sarah Friedl

Sarah has two Master's, one in Zoology and one in GIS, a Bachelor's in Biology, and has taught college level Physical Science and Biology.

In this lesson, you will learn about the different types and sources of water pollution. You will gain an understanding of both surface water and groundwater pollution and the similarities and differences between them.

What Is Water Pollution

Nothing is quite as refreshing as a glass of water. On a hot summer day, some ice water really does the trick. On a cold winter day, a nice cup of hot tea will take away the chill. Do you drink coffee in the morning? You need water for that, too!

We take for granted that we have easy access to clean water for drinking, washing dishes and cleaning our clothes, but water isn't always clean. A body of water, such as a lake, stream, river, pond, ocean and even the water underground in the soil, can become polluted when it's contaminated by sewage leaks, agricultural runoff or chemical spills. When water is polluted, it becomes unsafe for human consumption because the water contains dangerous or toxic substances and disease-causing bacteria and organisms.

Pollution may be caused by natural sources or human activities, but regardless of the cause, the result is the same. It can have detrimental effects on aquatic ecosystems as well as the health of those who depend on those sources of water, like us!

Pollution can be difficult to determine because it is not always visible, so scientists use a variety of techniques and tests to measure water quality and the level of contaminants.

Two Sources of Water Pollution

Though water pollution may occur from a variety of sources, there are two terms used to describe how the water became polluted.

When water is polluted from point sources, this is pollution from a discrete location. This discrete location could be a factory, a sewer pipe or a runoff from a single farm. The BP oil spill in 2010 is an example of point source pollution, because the massive amount of oil leaked from a single point of origin.

Water pollution may also be from non-point source pollution, which is when several points of contamination over a large area contribute to the pollution of a water body. For example, one water body may be contaminated by multiple sources like agricultural runoff, city street runoff, construction sites and residential lawns. The Mississippi River is at great risk for non-point source pollution because it is so large and is exposed to a variety of possible pollution sources.

Surface Water Pollution

Surface water pollution is the pollution of aquatic systems that are above ground, such as streams, lakes and rivers. These waters become polluted when rainwater runoff carries pollutants into the water. The pollutants transported by runoff are things like salts and chemicals from city and highway roads and nutrients and fertilizers from farms and lawns.

When pollution is caused by nutrients and fertilizers, this is called nutrient pollution, and it leads to an overproduction of algae and other aquatic plants. This overabundance of plants and algae causes problems, because they cover the water surface and prevent sunlight from reaching the plants underwater. This then leads to less oxygen production, which causes harm to oxygen-breathing organisms in the water, like fish.

Surface water may also be polluted with pathogens and waterborne diseases, which is usually the result of sewage leaks and runoff from animal factories. These viruses and bacteria that pollute the water may cause dangerous human health problems such as giardia, typhoid and hepatitis.

Interestingly, one way to monitor for this type of pollution is checking the water for fecal coliform bacteria, which comes from the waste of people and other animals. If the water is contaminated with this type of bacteria (which itself is not harmful to human health), it indicates that other types of bacteria that are very dangerous to humans may also present, because they often come from the same sources.

Toxic chemicals may also lead to surface water pollution. These come from pesticides, synthetic chemicals such as petroleum products and other car fluids, and mercury, lead and arsenic from mining site drainage. These chemicals are very dangerous for the environment as well as for the health of the organisms that inhabit them.

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