Watersheds

Watersheds

Middle School

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Learning Objectives

• Define a watershed and identify its key parts like divides and tributaries.

• Explain the difference between surface water and groundwater in the water cycle.

• Describe how human activities like runoff can pollute watersheds.

• Identify ways to protect water from point and nonpoint source pollution.

Key Vocabulary

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Watershed

An area of land that drains all its water into the same river, lake, or waterway.

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Divide

A ridge of high land that separates one watershed from another, directing the water flow.

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Tributary

A smaller stream or river that flows into a larger river or a large body of water.

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Runoff

Water from rain or snow flowing over the land's surface instead of soaking into the ground.

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Aquifer

An underground layer of rock or sediment that holds a large amount of groundwater.

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Permeable

A material that allows water to pass through, such as soil, sand, and gravel.

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What is a Watershed?

• A watershed is land where rain and snowmelt flow to one place.

• All this water drains into a common river, lake, or other waterway.

• Watersheds can be large for big rivers or small for little streams.

• Our actions affect the health of the soil, water, and plants there.

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Multiple Choice

Which statement best defines a watershed?

• The underground system of caves and rivers.

• A large body of water, like a lake or an ocean.

• An area of land where all water flows to a common waterway.

• A man-made structure for storing water.

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Parts of a Watershed

Divide

• A watershed’s boundaries are determined by the land's surface features, also known as topography.

• A divide is a ridge of high land that separates one watershed from another.

• Water on opposite sides of a divide will flow to two completely different areas.

Tributaries

• Tributaries are the smaller streams and rivers that all flow into a larger, main river.

• You can think of them as the branches that feed into the main trunk of a tree.

• Flowing water in tributaries erodes soil and rock, which forms small channels that can grow.

Multiple Choice

What is the role of a 'divide' in a watershed?

• It is a ridge of land that separates one watershed from another.

• It is the main river that all tributaries flow into.

• It is the place where freshwater and saltwater mix.

• It is a small stream that flows into a larger river.

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Surface Runoff and Groundwater

• All freshwater starts as precipitation from the sky, like rain or snow.

• Surface runoff is water that flows over the land into rivers and lakes.

• Groundwater is water that soaks deep into the ground, filling cracks in soil.

• Groundwater is a very important source of drinking water for people and farms.

Multiple Choice

What is the main difference between surface water and groundwater?

• Surface water comes from precipitation, while groundwater comes from the ocean.

• Surface water flows over the land, while groundwater is stored underground.

• Surface water is used for farming, while groundwater is only for drinking.

• Surface water is always saltwater, while groundwater is always freshwater.

Underground Water Systems

• Water easily passes through permeable materials like sand and gravel.

• Impermeable materials, like clay, block water from passing through.

• Aquifers are underground layers that hold large amounts of fresh water.

Multiple Choice

What is an aquifer?

• A well that is drilled to find water.

• The flow of water over the land's surface.

• An underground layer of permeable rock that holds water.

• A material like clay that does not let water pass through.

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Human Activities Can Pollute Watersheds

• Runoff from homes can carry fertilizers, pesticides, oil, and antifreeze.

• ​Urban runoff often contains industrial waste, cleaning products, and trash.

• This polluted water flows from storm drains into rivers and oceans.

• Clearing forests can also alter the natural water cycle balance.

Multiple Choice

According to the slide, how can a resident living far from the ocean contribute to ocean pollution?

• By using too much electricity at home.

• By overwatering their lawn, which creates runoff that flows into storm drains.

• By planting trees in their yard.

• By visiting the beach and leaving trash behind.

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Sources and Effects of Pollution

• Point source pollution is from a single source, like a factory pipe.

• Nonpoint source pollution comes from many places and is hard to trace.

• Excess nutrients create dead zones where fish cannot get oxygen to survive.

• Trash can entangle wildlife, and chemicals can poison aquatic animals.

Multiple Choice

What is the key difference between point source and nonpoint source pollution?

• Point source comes from farms, while nonpoint source comes from factories.

• Point source can be traced to a single location, while nonpoint source cannot.

• Point source is harmless, while nonpoint source is toxic.

• Point source is always liquid, while nonpoint source is always solid.

​How Can We Help?

• ​Properly dispose of all household waste and chemicals.

• Avoid overwatering your lawn and use fertilizers sparingly.

• Always pick up and properly dispose of pet waste.

Multiple Choice

Which of the following is a recommended way to protect our water supply?

• Properly dispose of household wastes instead of putting them down the sink.

• Leave pet waste on the grass to decompose naturally.

• Wash your car at home to save water.

• Use extra fertilizer on your lawn to make it greener.

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Common Misconceptions About Water Quality

Misconception	Correction
Only people living near water can affect its quality.	Actions far away can pollute water because everyone lives in a watershed.
Water in storm drains gets cleaned before entering rivers.	Most storm drains flow directly into waterways without any treatment.
Groundwater is always pure because the soil acts as a filter.	Harmful chemicals can seep through soil and contaminate our drinking water.
Small oil or chemical leaks don't cause much harm.	Even small leaks are very toxic to fish and other aquatic life.

Multiple Choice

How does the permeability of the ground affect the balance between surface runoff and groundwater recharge in a watershed?

• Highly permeable ground increases surface runoff by pushing water upwards.

• Impermeable ground increases groundwater recharge by trapping water.

• Highly permeable ground increases groundwater recharge and reduces surface runoff.

• Permeability has no effect on the balance between runoff and groundwater.

Multiple Choice

Why are excess nutrients from fertilizers considered a major pollutant in watersheds?

• They make the water too salty for freshwater organisms.

• They cause algae blooms that deplete oxygen, harming fish populations.

• They prevent sunlight from reaching aquatic plants.

• They directly poison fish and birds that drink the water.

Multiple Choice

A new suburban neighborhood is built, replacing a forest. Predict the most likely impact on the local watershed's water quality and explain the cause.

• Pollution will likely increase due to residential runoff from lawns and driveways.

• Water quality will improve because there are fewer wild animals.

• The amount of groundwater will increase because of the new buildings.

• There will be no significant impact on the watershed.

Multiple Choice

If a factory is discovered to be releasing chemicals through a pipe into a river, what type of pollution is this, and why is it sometimes considered easier to manage than other types?

• Point source pollution; it's easier to manage because the single source can be identified and regulated.

• Residential pollution; it's easier because homeowners can be educated.

• Agricultural pollution; it's easier because farmers can change their practices.

• Nonpoint source pollution; it's easier to manage because it comes from a wide area.

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Summary

• A watershed drains water into one waterway and is fed by tributaries.

• Water travels as surface runoff or soaks in to become groundwater.

• Human activity causes both point and nonpoint source water pollution.

• We can protect watersheds by conserving water and disposing of waste properly.

Poll

On a scale of 1-4, how confident are you about the concepts covered in today's review?

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• 4