RS: Groundwater and Watersheds

Groundwater and Watersheds

Student Objective

I can explain how humans depend on and impact watersheds.

Watersheds

Watersheds are an important natural resource for many wildlife and

ecosystems. They are also vital to the everyday lives of people. Everyone in the world, no matter where they are, lives in a watershed and depends on its resources. In the United States, groundwater supplies about a third of freshwater for human use. The rest comes from surface water, such as rivers, streams, creeks, lakes, and reservoirs. What exactly is a watershed and why are watersheds important? What would happen if watersheds are poorly managed or did not have protection?

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Discuss with your partner

How should we manage watersheds?

How can humans impact watersheds positively or negatively?

Everyone, everywhere in the world, lives in a watershed! All land can be divided into watersheds. A watershed is a region of land that channels and drains water into a common body

of water such as a reservoir, bay, or ocean. Because of this, watersheds are sometimes called drainage basins. For example, water from high elevations flows through rivers to lower

elevations. Rivers can empty into other bodies of water such as larger rivers, lakes, or the ocean. All of the land area that collects

and feeds water into the same body of water forms a watershed.

Each watershed is separated by the areas of high elevation or ridges

that form its borders. Watersheds supply clean water to communities

and agriculture, support habitats for wildlife, and provide water for

industry and recreation. It is therefore important that they are protected from the adverse effects of pollution and other human activities.

Some watersheds include wetlands, such as swamps, marshes, and

bogs. These bodies of water can help maintain water quality by

collecting and filtering out sediment and pollution from water. They

also provide important ecosystems and habitats for many different

kinds of plants and animals. These areas can also absorb excess

water from storms and runoff to prevent flooding.

Answer these questions related to the passage:

• How is a watershed different from a river or lake?

• What information would you use to convince people not to fill in wetland areas?

Groundwater

Only three percent of Earth’s water is freshwater, with most of it

frozen in glaciers and polar ice caps. Groundwater makes up one

percent of Earth’s water, while all of the surface waters—such as

rivers, streams, and lakes—make up just 0.03 percent. When rain

falls onto land, three things can happen. The water can evaporate

from the surface; run along the surface into streams and rivers; or it

can soak into the ground. Where does the water that soaks into the

ground go, and why is it so important to us?

Water that soaks into the ground can infiltrate deep into underground reservoirs called an aquifer. Aquifers are made of porous or permeable rocks that can soak up water, similar to a sponge. Aquifers are usually made of porous rocks like sandstone, limestone, gravel, or sand. A confined aquifer is sandwiched between a top and bottom layer of impermeable material. This

creates a lot of water pressure in the aquifer. When it is penetrated by a well, water rises above the top of the aquifer. Aquifers can also sometimes come to the surface to release water at a spring.

A water table is the boundary that separates an aquifer from the soil or ground above. If the water table reaches the surface, it may form a pond, lake, or river.

Answer these questions related to the passage:

What is an aquifer?

What is a water table?

Human Impacts on Water

Aquifers are natural water purifiers that trap sediment and microbes in the groundwater flowing through them. In fact, aquifers provide about a third of the nation’s freshwater for drinking and agriculture. Hydrologists and water managers use precipitation data, river gauges, evaporation rates, radar and other data to plan efficient and safe use of this natural resource so people always have access to water.

Precipitation, in the form of rain and snow, adds water to an aquifer, a process called recharging. Surface waters may also help to recharge aquifers. The rate of recharge of an aquifer depends upon the rainfall and also on the nature of the rock overlying the aquifer. If the overlying rock is impermeable, water will not easily get into the aquifer. Pumping water too fast decreases the water in an aquifer—a process called drawing down. If pumping exceeds recharging, the

amount of water in an aquifer will decline.

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Human Impacts on Water

Human activities can have broad-reaching impacts on watersheds and aquifers. Manmade products such as oil, road salts, gasoline, and chemical wastes can sometimes seep into aquifers or other groundwater sources and contaminate them. Stormwater runoff is one of the most significant threats to ecosystems along the coastal areas of the United States. As the water runs over and through the watershed, it picks up and carries contaminants. Water pollution comes from

many sources, including motor oil on parking lots, plastic grocery bags, pesticides, fertilizers, and detergents. All can wash directly into waterways and be carried down the watershed into larger bodies of water, including the ocean. This pollution is linked to the creation of large dead-zones in the ocean and also threatens coral reef ecosystem health around the world.

Human Impacts on Water

Protection of groundwater resources is essential. Some of the action that can be taken starts at home. Care should be taken when disposing of harmful household chemicals—such as paints, herbicides, insecticides, and some cleaning products. Rather than dumping these down the sink or toilet, they should be taken to a waste disposal facility. Everyone can help conserve water. About three-quarters of the water used in the home is used in the bathroom. About a third is used in the shower. Most water used in the home literally goes down the toilet. There are many ways people can help to conserve and manage water resources, such as reducing pollution and waste or shortening the time spent in showers.

Think about what you read and answer the following questions about the passage:

What are some ways that aquifers can be replenished?

What can people do in the home to conserve water?

Multiple Choice

How would you describe the journey of a drop of water once it lands in a watershed?

• The journey of a drop of water in a watershed involves flying through the air like a bird
• The journey of a drop of water in a watershed involves transforming into a solid rock
• The journey of a drop of water in a watershed involves flowing over land, seeping into the ground, evaporating, being taken up by plants, and eventually reaching a body of water.
• The journey of a drop of water in a watershed involves disappearing into another dimension

Multiple Choice

How are watersheds and groundwater related?

• Watersheds have no impact on groundwater levels
• Groundwater is not affected by watersheds
• Watersheds lead to groundwater depletion
• Watersheds can contribute to groundwater recharge by allowing precipitation to infiltrate the ground.

Multiple Select

What positive and negative impacts can humans have on watersheds? Pick THREE.

• Humans can positively impact watersheds by implementing sustainable land use practices and restoring wetlands.

• Humans negatively impact watersheds by conserving wetlands
• Humans negatively impact watersheds by promoting deforestation

• Humans positively impact watersheds by increasing pollution levels
• Humans negatively impact watersheds by urbanization, and pollution from industrial activities

Multiple Choice

Why is it important to manage and protect watersheds?

• Protecting watersheds does not contribute to ecosystem health
• There are no benefits to regulating water flow in watersheds
• Protecting watersheds ensures a sustainable supply of clean water, supports ecosystems, and reduces pollution.

• Managing watersheds has no impact on water quality

Match

 Look at the graph and match the approximate percentages of Earth’s water to each category.

• Salt water

• Glaciers and ice sheets

• Groundwater

• Freshwater

98 percent

87 percent of freshwater

12 percent of freshwater

2 percent

• 98 percent

• 87 percent of freshwater

• 12 percent of freshwater

• 2 percent

Multiple Select

Based on the graph, which of the following statements are true? Select THREE.

• The public water supply uses the most water per day.

• Irrigation uses 53,500 million gallons of water per day.

• Power plants and aquaculture use similar amounts of water.

• Irrigation uses more water than all of the other uses combined.

• Mining uses less than 2,000 million gallons per day.

Dropdown

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are regions of land that channel water into a reservoir, bay, or ocean. They are separated by the areas of high elevation that form their borders. When rain falls onto land, the water can evaporate from the surface, run along the surface into streams and rivers, or soak into the ground. Water that soaks into the ground can infiltrate deep into underground reservoirs called ​

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, and ​

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are the boundaries that separate them from the soil or ground above.