What Are Watersheds? Why are They Important to You and Your Family?

Steps You Can Take to Protect Water

Drip. Drip. Tiny drops of cleaning fluid drip into a stream from a factory pipe. As the stream meanders through a watershed, it’ll empty into a larger river and eventually reach the ocean. This chemical traveled through a watershed and is contaminating the water along the way . But what is a watershed, and why should we protect the land and water near it?

Watershed of the Enguri River, Georgia in Eastern Europe
Watershed of the Enguri River, Georgia in Eastern Europe, Credit: kotenko/123rf.com

Table of Contents

What is a watershed?

Watershed. Credit: Wikimedia/ U.S. Government Accountability Office/Tyler ser Noche

Have you ever hiked a wilderness path near a bubbling stream? If you have, you’ve walked through a watershed.


A watershed, or drainage basin, is the area of land through which water drains and flows into a body of water. Water travels across the ground when it rains or when snow melts. Watersheds drain into various types of bodies of water such as streams, rivers, lakes, ponds, and oceans. The small stream that you hike around connects with a river and is a part of its watershed. This water normally flows from a high elevation to a lower elevation, or downstream.


There are various types of watersheds: forest, coastal, desert, mountain, or, if you live in the city, an urban watershed. Which type are you living in right now?

Which watersheds can you name?

The Amazon River Basin
The Amazon River Basin, Credit: Wikimedia/Kmusser

Now that you know what a watershed is, let’s look at some of the largest watersheds in the world.


● The Amazon River watershed is the largest one that you may know. It tops out at 2.7 million square miles (7 million km2).


● In North America, the Mississippi River has captured the title for the largest watershed, coming in with 1.5 million square miles (3.2 million km2).


● The Congo Basin is the largest watershed in Africa, taking up a whopping 1.3 million square miles (3.4 million km2).


● Asia comes in at 307,000 square miles (795,000 km2) for its Mekong River water basin.

What are the benefits of watersheds for you?

Watersheds are a natural resource that requires protection. Besides purifying water, watersheds provide habitats for diverse species of plants, animals, and insects, as well as recreation (camping, fishing, boating). Since water is crucial for all living organisms, we need healthy watersheds.


Think of a watershed as an enormous sponge. The plants, roots, and ground litter (such as decayed leaves) work to absorb rainwater deep into the ground, where it is filtered and stored in aquifers—areas of permeable rock that hold groundwater. Aquifers are tapped for our drinking water, and farmers use this water to irrigate their plants during dry months. Water travels through the watershed and empties into tiny streams that finally discharge into large rivers, like the Mississippi River.

The pond is inhabited by red-eared slider terrapin (Trachemys scripta elegans) and carp. City of London Cemetery, Aldersbrook Road, Newham, England.
The pond is inhabited by red-eared slider terrapin (Trachemys scripta elegans) and carp. City of London Cemetery, Aldersbrook Road, Newham, England, Credit: Wikimedia/Acabashi

All organisms need a healthy watershed full of flourishing plants and clean water for survival. A rainforest watershed provides opportunities for species like anteaters and jaguars to complete their life cycles, feed, and find shelter. In comparison, a fox, opossum, or bobcat require a woodland watershed to live. Taking care of the soil and vegetation in a watershed ensures the well-being of the wildlife living there.


Watersheds promote the cycling of necessary nutrients in our ecosystems. These nutrients include nitrogen, phosphorus, and carbon. The cycling of these nutrients is necessary for the growth and survival of organisms.

What is happening to our watersheds?

Water Pollution
Water Pollution, Credit: pixnio.com/Goldman Luther C, USFWS

Clean water is in danger from careless use and disregard of our watersheds. Let’s look at some facts.


In the world, there are approximately 1.1 billion people with no access to safe drinking water. Around 2.6 billion people don’t have water for toilets, showers, or sinks. And one of the most shocking facts is that in some countries, 90% of sewage is dumped right into bodies of water. It’s estimated that over  3.4 million people worldwide die from waterborne illnesses each year.


How does this happen? One cause of impure water is runoff. Runoff, or excess water that flows across the ground, picks up various chemical pollutants, garbage, bacteria, and sediments. Microplastics, fragments of plastic smaller than 5 mm, also float through the runoff. Tiny bits of rubber in the water are a common problem found in urban runoff. these pollutants are distributed into a body of water, causing harm and possibly diseases. Rainwater and melted snow travel down our streets, across paved parking lots containing grease and oil, through muddy farms, and over chemically treated lawns. The water flows through gutters where it gathers litter. It pours into storm drains and passes over ditches, picking up various other pollutants. No wonder our rivers and lakes can become polluted.


Sediments, including salts, pesticides, oil, and litter, are the number one cause of pollution in our watersheds. Sediments kill fish by suffocating them, as their gills become blocked. Mercury (Hg), a liquid metal, can spill from factories and refineries into the water. Mercury accumulates in fish, and, when eaten by a pregnant woman, may cause damage to the nervous system of an unborn baby.


Japanese people were exposed to high levels of mercury in the 1950’s when a local factory dumped an estimated 27 tons of mercury compounds into Minamata Bay. Citizens ate the poisoned fish from the bay. The mercury contamination caused Minnamata disease, a neurological disease characterized by loss of vision, loss of hearing and loss of coordination.


Infants were born with deafness, deformed limbs, mental retardation, and blindness. Minnamata citizens are still feeling the effects of this ecological disaster today.


Runoff from agricultural sites contains the bacteria E. coli (Escherichia coli) from cattle manure. After water runs over farmland, accumulating the waste, bacteria spill into rivers and lakes, resulting in dangerous health issues for people who might be boating or swimming.


Another detriment of agriculture is overgrazing by cattle. Overgrazing increases soil erosion, which causes the destruction of streambanks and encourages invasive species to grow. Farmers use insecticides, herbicides, and fungicides to protect their plants from pests. These chemicals run off into the water. Fish and wildlife that use the water for survival are exposed and often killed by these poisons.

Videographer filming acid mine runoff in a stream
Videographer filming acid mine runoff in a stream, Credit: pixnio.com/Hagerty Ryan, USFWS

What can you do to change this situation?

We all need clean water, not only for drinking, but for daily routines such as cooking and recreational enjoyment. But what can you do to protect a watershed? You can make a positive impact on your watershed by implementing small steps each day. Here are a few to get you started:


● Don’t pour chemicals in your drains; drop them off at hazardous waste sites in your county


● Plant trees that help prevent erosion (and provide the added benefit of photosynthesis)


● Reduce water use in your home by decreasing shower time, and take showers instead of baths (the average bath uses 35 to 50 gallons of water, while a 10-minute shower with a low-flow showerhead only uses 25 gallons)


● Recycle lawn clippings and leaves to prevent them from entering drains


● Discontinue fertilizers on your lawn, or use an organic fertilizer


● Don’t dump oil, gas, or antifreeze into the street or gutters


● Pick up trash and waste if you see it collecting in your yard or storm drains

Conserve water and avoid runoff in order to protect your watershed. Take care of the streambeds and riverbanks. All of the work will pay off in the end with fresh and clean water. If you maintain your watershed now, it will be healthy for humans and wildlife in the future.


aquifer:  An underground layer of rock that water can move through and be stored there


detriment: Harm or damage


irrigate: To supply plants or crops with water through pipes or channels


nutrients: A substance that gives energy and promotes growth to living organisms


sewage: waste, such as liquid or solid, that flows through sewers


sediment: matter that settles to the bottom of a liquid


neurological: having to do with the nerves or nervous system

Flesch Kincaid Grade Level: 7.7


Flesch Kincaid Reading Ease: 63.3

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Caleb Aldridge and Beth Baker. March 9, 2020. Watershed: Role, Importance and Stewardship Wildlife, Fisheries, and Aquaculture. Mississippi State University. Retrieved November 02, 2022 from http://extension.msstate.edu/publications/watersheds-role-importance-stewardship


Deaths from Dirty Water and Related Diseases. The World Counts. Retrieved November 3,2022 from https://www.theworldcounts.com/challenges/planet-earth/freshwater/deaths-from-dirty-water.


How We Protect Our Wetlands. The Nature Conservancy. Retrieved October 31, 2022 from



M. Harada. 1995. Minamata disease: methylmercury poisoning in Japan caused by environmental pollution. Retrieved November 3, 2022 from https://pubmed.ncbi.nlm.nih.gov/7734058/


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  • Lisa Endicott
    : Author
    My passion for science is rooted in my love and curiosity for nature and animals. I have successfully taught biology, health and English as a Second Language classes for 27 years in Madison, Wisconsin. I earned degrees in Biology and Life Science education along with a Masters in reading education from the University of Wisconsin, La Crosse. I completed my English as a Second Language certificate at the University of Wisconsin, Madison. I find teaching most rewarding when students dig deeper into lessons to answer their own questions. I am excited to write for Smore Science to share the extraordinary world of science. Young women, you belong in STEM careers. We need your voices and your talents. Embrace risks and challenge yourselves.

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