Water Cycle+ Watersheds

Water Cycle+ Watersheds

Middle School

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Learning Objectives

• Describe the main stages of the water cycle: evaporation, condensation, and precipitation.

• Explain the Sun's important role in powering the water cycle.

• Identify how water changes its state between solid, liquid, and gas.

• Identify the roles of water and land within a watershed system.

• Describe abiotic and biotic factors in an ecosystem.

Key Vocabulary

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Water Vapor

The invisible, gaseous form of water in the atmosphere, also known simply as water in the air.

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Watershed

An area of land that drains or sheds all of the runoff to a particular body of water.

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Aquifer

An underground layer of rock that can hold a large amount of water, like a natural underground reservoir.

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Estuary

A partially enclosed body of water where fresh water mixes with salt water from the ocean.

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Biotic Factors

The living or once-living parts of an ecosystem, such as plants, animals, fungi, and even bacteria.

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Abiotic Factors

The non-living parts of an ecosystem, including water, temperature, wind, air, soil, and sunlight.

The Water Cycle and States of Water

• Water moves between Earth and the atmosphere in the water cycle.

• It changes between solid (ice), liquid (water), and gas (water vapor).

• Sunlight provides the energy that drives the water cycle and its changes.

Multiple Choice

What are the two primary forces that drive the continuous movement of water in the water cycle?

• Temperature and pressure

• Sunlight and gravity

• Wind and ocean currents

• Moonlight and magnetism

Key Processes of the Water Cycle

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Evaporation

• ​Liquid water is heated by the sun and changes into a gas.

• ​​This gas, known as water vapor, rises up into the air.

• ​When ocean water evaporates, the salt content is left behind.

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Transpiration

• ​Water evaporates from plants and trees into the air.

• ​​It is water vapor given off by plants as a waste product.

• ​This process also adds more water vapor to the atmosphere.

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Condensation

• ​Water vapor in the air cools and becomes liquid water droplets.

• ​​It can also form ice crystals through the process of crystallization.

• ​These droplets and crystals group together to form clouds.

Multiple Choice

Which process is responsible for the formation of clouds from water vapor?

• Transpiration

• Precipitation

• Evaporation

• Condensation

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From Clouds to Ground: Water's Journey

• Gravity causes water to fall from clouds as rain, snow, sleet, or hail.

• On land, gravity pulls water to flow from higher to lower areas.

• Runoff is water flowing over land that is saturated or impermeable.

• Water soaks into the ground through infiltration, becoming groundwater for wells and springs.

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Multiple Choice

What is it called when water soaks into the ground to become groundwater?

• Condensation

• Runoff

• Infiltration

• Precipitation

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Understanding Watersheds

What is a Watershed?

• A watershed is a land area that drains all its water to the same river, lake, or stream.

• Its boundary, a high point of land called a divide, is shaped by the land's topography.

• Smaller streams or rivers that flow into a larger one within a watershed are called tributaries.

Permeable vs. Impermeable

• Permeable materials, like soil and sand, have spaces that allow water to soak into the ground.

• Impermeable surfaces, such as solid rock or clay, do not let water pass through them.

• Water on these surfaces becomes runoff, flowing over the land instead of soaking into the ground.

Multiple Choice

The boundary of a watershed is called a 'divide' and is determined by what feature?

• The type of soil

• The location of rivers

• The amount of rainfall

• The topography of the land

Related Ecosystems and Features

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Aquifer

• An aquifer is an underground layer of permeable rock or sediment.

• It holds a large amount of groundwater, like sand or gravel.

• People drill wells into aquifers to get fresh drinking water.

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Estuary

• An estuary is a coastal body of water with brackish water.

• This is where freshwater from rivers mixes with ocean saltwater.

• The unique mix of water creates a special, diverse habitat.

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Wetlands

• Wetlands are land areas like bogs, marshes, or swamps.

• The land is saturated with water for part of the year.

• They are important for stopping runoff and neutralizing any toxins.

Multiple Choice

What is the defining characteristic of an estuary?

• It is a mix of freshwater and saltwater.

• It is a small channel flowing into a river.

• It is a large underground water source.

• It is land covered in water all year.

Human Impact on Ecosystems

• Harmful runoff pollutes our water systems.

• Pollutants can cause large algal blooms.

• This harms fish and other aquatic life.

Multiple Choice

A municipal water system draws water from a river downstream of several residential areas with outdated sewage infrastructure. Which of the following classes of organisms found in the water poses the most direct and immediate threat to human health through consumption?

• Algal blooms (phytoplankton)

• Aerobic bacteria responsible for BOD

• Fecal coliform bacteria and associated pathogens (e.g., E. coli, Giardia)

• Zooplankton populations

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Common Misconceptions

Misconception	Correction
Clouds are made of water vapor.	Clouds are made of tiny water droplets or ice crystals.
The water cycle has a starting point.	The water cycle is a continuous loop with no true beginning or end.
Water disappears when it evaporates.	Water changes its state from a liquid to a gas.

Multiple Choice

A municipal water system draws water from a river downstream of several residential areas with outdated sewage infrastructure. Which of the following classes of organisms found in the water poses the most direct and immediate threat to human health through consumption?

• Algal blooms (phytoplankton)

• Aerobic bacteria responsible for BOD

• ecal coliform bacteria and associated pathogens (e.g., E. coli, Giardia)

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  D) Zooplankton populations

Multiple Choice

Why are wetlands considered crucial for the health of a watershed?

• They are large, impermeable areas that prevent infiltration.

• They increase the speed of water flowing to rivers.

• They are the primary source of saltwater for estuaries.

• They slow down runoff and help filter out pollutants.

Multiple Choice

A town near a lake experiences a massive bloom of algae that harms fish populations. Based on your knowledge of watersheds, what is a likely cause?

• A decrease in the water temperature of the lake.

• The construction of a new well to tap into groundwater.

• Runoff carrying excess fertilizers from nearby farms or lawns.

• An increase in the amount of salt in the lake.

Multiple Choice

If a large forest in a watershed is replaced with a shopping mall with large parking lots, what is a probable consequence for the local water system?

• Decreased surface runoff and increased water infiltration into the ground.

• An improvement in local water quality due to less soil erosion.

• The formation of a new aquifer under the parking lot.

• Increased surface runoff leading to a higher risk of river flooding, and decreased groundwater recharge.

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Summary

• The sun and gravity drive the continuous water cycle.

• Water changes between solid, liquid, and gas states.

• A watershed is an area that drains water to a common body of water.

• Human activities can harm water quality, but wetlands and aquifers help filter it.

Poll

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

• 1

• 2

• 3

• 4