Watershed Ecosystems

Watershed Ecosystems

6.7 - WatershedsName______


An ecosystem is made up of living things and nonliving things that interact with one another in a certain place. The living, or once-living, parts of an ecosystem are called biotic factors. Biotic factors include plants, animals, bacteria, and fungi. The non-living parts of an ecosystem, such as light, temperature, weather, soil, water, oxygen, carbon dioxide, and minerals, are an ecosystem’s abiotic features.

Different habitats exist within each ecosystem. A habitat is the kind of place where an organism lives. It supplies all the biotic and abiotic factors that the organism needs in order to survive.

One type of ecosystem found in Virginia is a watershed ecosystem. A watershed is an area of land that drains into a stream, river, lake, or other body of water. A watershed is also called a drainage basin.

Watersheds are separated from each other by higher land areas called divides. Mountain ridges make up many divides. For example, ridges of the Rocky Mountains famous Continental Divide.

Watersheds can include rivers, streams, lakes, and wetlands. A stream is a small body of water that is fed by other smaller streams, or tributaries. A lake is a low area of land where the surface collects. A lake is a low area of land where surface water collects. Lakes vary greatly in size. A wetland is a land area that remains wet for all or part of the year.


List 3 biotic and 3 abiotic factors found within your home.



1. Which of the following is an abiotic factor that all organisms need to survive?

A. rocksB. sunlight

C. treesD. temperature

2. Which of the following is a biotic factor?

A. waterB. sunlight

C. treesD. temperature

3. What is a habitat?

A. all the living things in an ecosystem

B. all the nonliving things in an ecosystem

C. the role of an organism in its environment

D. the place where an organism lives






PRACTICE – In the following pictures, circle all the biotic features and list all the abiotic features.

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You might say that biotic factors are the life of an ecosystem and abiotic factors are its health. The health of an ecosystem depends on the quality of its abiotic factors. To thrive, living things must be healthy and safe. Good water quality is one factor that promotes a healthy environment. Poor water quality limits where plants and animals can live and how people can use an area.

Watershed ecosystems provide abundant food and water for humans and other organisms. These ecosystems are fragile and can be damaged or destroyed by human activities. The land features in the watershed affect the quality of all water that falls in the area and drains through it.

If the land is developed too much, with many public buildings and roads, the water will flow too quickly and not drain through the soil. This is a major cause of flooding and increased erosion. Erosion is the process by which water and wind pick up soil and larger sediment and move them to a new location. Plowing and construction can expose soil in an area. When plants are removed, their roots can no longer hold the soil in place. Then flowing water can erode the soil and damage the ecosystem. Eroded soil can was into, choke, and pollute rivers and streams.

As rivers and streams flow across the land, they also pick up pollutants. Fertilizers and pesticides overused in agriculture can end up in the drinking water supply and damage habitats. Chemicals that are not properly discarded also damage water. So does human waste that is not properly treated.

Industries and individuals can damage watersheds, but they can also protect watersheds. Many farmers use plowing techniques that reduce erosion. Some farmers limit their use of fertilizers. Companies can make sure the water they release has been properly treated. They can also safely dispose of chemicals.

People can reduce their use of fertilizers and pesticides on lawns. Then less of these substances will end up in local streams and lakes. Individuals can sweep up and collect sediment from streets or sidewalks to keep it from entering storm drains. Homeowners can make sure that their wastewater pipes do not empty directly into a lake or stream. Car and truck owners can check to make sure their vehicles do not leak fluids. Everyone can play a role in keeping watersheds healthy and safe.


Explain how increased erosion can affect one biotic factor and one abiotic factor in a watershed ecosystem.



1. One way people can prevent water pollution is

A. by constructing more building and roads

B. by using more fertilizers and pesticides

C. by planting fewer trees

D. by making sure their vehicles do not leak fluids

2. How did DDT affect Virginia’s watershed ecosystems?

A. it contaminated crops grown along the James River

B. it caused bald eagles and osprey to become almost extinct

C. it had no effect on Virginia’s watershed ecosystems

D. it made swimming in the Potomac River unsafe for people




Virginians rely on the state’s three major watersheds to supply most of their freshwater. People in Virginia use more than 5,467 million gallons of freshwater each day. That amounts to about 826 gallons used daily by each Virginia resident.

What happens when Virginia’s water supply is put at risk? In the mid-1900’s, humans and other organisms faced health risks from pollution of Virginia’s waters. Fish in the James were contaminated by a cancer-causing chemical disposed of illegally. Pollution from sewage in the Potomac River made the water unsafe for swimming. The bald eagle and osprey almost become extinct because of DDT pollution. DDT is a pesticide that washed from farmland into water bodies and was taken in by organisms in the bird’s food web.

Today, the most serious threats to Virginia’s water quality are pollutants carried by storm runoff from farms and developed lands such as streets, parking lots, lawns, and construction sites. Pollutants carried by runoff include fertilizers, manure, chemicals and sediments. But Virginians have taken steps to protect the state’s water. In 1997, the Virginia General Assembly passed the Water Improvement Act to help pay for programs that improve water quality. The risk for humans of exposure to harmful pollutants has dropped. Bald eagles and osprey are once again fishing in Virginia’s waters.

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No matter where you live in Virginia, you live in one of the state’s many watersheds. Remember that a watershed is an area of land that drains into a stream, river, lake or other body of water. Small watersheds make up larger watersheds, which drain into larger bodies of water.

Most of Virginia’s watersheds are named for the river they drain into. Each of the watersheds shown on the map is made up of smaller watersheds that drain into streams and ponds, these watersheds show also make up larger watersheds.

Most of Virginia’s watersheds are part of three other, very large watersheds – the Chesapeake Bay Watershed, the North Carolina Sounds Watersheds, or the Mississippi Watersheds. These watersheds also extend into other states.

The Chesapeake Bay Watershed, covering the northern part of the state, is Virginia’s largest watershed. More than half of the state drains into the Chesapeake Bay. A bay is a body of water partly enclosed by land. The Chesapeake Bay opens into the Atlantic Ocean.

Within Virginia’s drainage basins, water occurs on the surface, as groundwater in aquifers. The table below lists some facts about Virginia’s watersheds:

Surface Water / Rivers & Streams / More than 50,000 miles of rivers & streams in 9 major river basins
Lakes / 450 public and private lakes, covering 322,000 acres
Springs / 1,600 springs (100 of them yield more than 450 gallons per minute)
Wetlands / 1,000,000 acres, decreased from 1.8 million acres in 1780
Groundwater / Aquifers / Supply drinking water, through wells, to about 2 million residents (34%)


How could water from all three of Virginia’s major watersheds end up in the same body of water?



1. In VA, which of the following is the largest watershed?

A. North Carolina Sounds Watershed

B. Mississippi River Watershed

C. James River Watershed

D. Chesapeake Bay Watershed

2. Which of the following drains into the Gulf of Mexico?

A. North Carolina Sounds Watershed

B. Mississippi River Watershed

C. James River Watershed

D. Chesapeake Bay Watershed

3. Which watershed do we live in?

A. James River Watershed

B. York River Watershed

C. Eastern Shore Watershed

D. Lower James Watershed



PRACTICE – In the picture of the watershed, list all the known pollutants.


A system is a group of parts that work together. The parts are often smaller themselves. In the last lesson, you learned how small watersheds make up larger watersheds. Within each watershed, small bodies of water flow through into larger bodies of water.

A river system is made up of a river and all its tributaries. Recall that a river a river is large, flowing stream of water that is fed by smaller bodies. These smaller bodies are streams, or tributaries. A stream is a small body of freshwater. A tributary is a smaller river or stream that feeds into a larger river.

Runoff from precipitation trickles down from higher elevations to lower areas. The water collects and forms small streams. Pulled by gravity, the small streams flow downward. The small streams flow into larger streams, which flow into a river. Small rivers flow into larger rivers, until at last the water reaches the ocean.

A river has different parts. Its headwaters are its beginning, or source. The headwaters of rivers are often in mountain ranges. The mouth of a river is its end – the place where it flows into a larger river, a lake, or an ocean. Most rivers and streams do not flow in a straight line. They form loops, or meanders, where the flow of water changes direction.

Rivers form in valleys – long depressions in Earth’s surface. As a river system forms, it changes the shape of the land. Flowing water carries soil and larger pieces of rock and deposits this sediment in new places. A river can carve out a canyon, a deep, narrow valley with steep sides. A river can also create a floodplain, a flat area of land formed when a river overflows its banks and deposits sediment.


A river system can be broken into 3 parts: Upper, Middle & Lower. Describe which features you would be able to find in each section.



1. Why are river and its tributaries a system?

A. they form a group of parts that work together

B. they each have a beginning and a end

C. they drain into a larger system, such as an ocean

D. the water in them moves only in one direction

2. A river forms in a long depression in Earth’s surface called a

A. meanderB. tributary

C. streamD. valley

3. What is the source, or the beginning, of a river called?

A. mouthB. meander

C. floodplainD. headwaters

4. Which term means a bend in a river or stream where the water changes direction?

A. tributaryB. meander

C. valleyD. canyon



PRACTICE – Break the river into the 3 sections (Upper, Middle & Lower) and give a description of each section.

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Chesapeake Bay is a unique and special place. It is the largest estuary in the United States, and it is surrounded by wetlands. Marshes and swamps are examples of wetlands. Wetlands are areas that remain wet for all or part of the year. They are found between areas of dry land and bodies of water, such as rivers, ponds, lakes, and bays.

Many wetlands contain freshwater. You can find these wetlands on the floodplains beside rivers and streams, along shorelines of lakes and ponds, and filling some depressions. Common organisms that live in freshwater wetlands include ducks, geese, deer, cattails, and trees, such as willow and birch.

Other wetlands are tidal wetlands. They are affected by twice-daily changes on incoming and outgoing tides. The water in tidal wetlands is a mixture of fresh and salt water. In Virginia, these wetlands are found along the shores of the Chesapeake Bay and its tidal rivers. Virginia’s tidal wetlands are home to waterfowl, shore birds, flounder, sea trout, striped bass, oysters, blue crabs, cattails, and cordgrass.

People have drained, filled, paved and constructed buildings on many wetlands. Each time we do so, we lose something that benefits us and other organisms. Wetlands are habitats for plants and animals. They provide organisms with the food and shelter necessary for survival. They serve as nesting places and nurseries for young animals.

Wetlands also act as sponges in the landscape. They slow down, collect, and hold rainwater. This property of wetlands helps prevent flooding and erosion. Wetlands improve water quality by filtering out pollutants and sediments. Coastal wetlands help protect inland areas from storm damage.

Estuaries are bodies of water in which freshwater from rivers and streams meets and mixes with salt water from the ocean. Chesapeake Bay is the largest estuary in the US. The bay is open to the Atlantic Ocean near Norfolk, Virginia. In the bay, this ocean water mixes with the freshwater draining from surrounding land. Estuaries are generally protected from ocean waves by barrier islands, reefs, or sand spits. The calm waters of the estuary are rich in dissolved oxygen, nutrients, and minerals supplied by the river water.

Just how much salt is in the water changes all the time. The animals in the estuary must be able to live in water that contains different amounts of salt throughout the day. Sea grasses provide food and shelter. Fish, shrimp, crabs, clams, and other shellfish thrive in these conditions. In fact, estuaries serve as nurseries for many of these animals. The Chesapeake Bay, in particular, is home to many different kinds of plants and animals.

People rely on estuaries for many things. For example, Chesapeake Bay is an important food source. It produces 500 million pounds of seafood each year. People also use the bay for recreation, including boating and fishing. Keeping pollution out of the bay is one way to preserve this natural resource and keep it safe for people and other organisms that rely on it.


What would happen to an estuary if the barrier islands, reefs, or sand spits near the estuary were removed?



1. What are wetlands?

A. bodies of water in which freshwater meets and mixes with salt water

B. parts of the ocean that are primarily surrounded by land and usually larger than a bay

C. land areas that remain wet for all or part of the year

D. areas of land drained by river systems

2. How do wetlands prevent flooding?

A. they act like sponges to hold floodwater

B. they help mix floodwater with ocean water

C. they move floodwaters to higher ground

D. they block floodwaters from reaching buildings

3. How are estuaries different from lakes and the ocean?

A. estuaries contain only salt water

B. estuaries contain only freshwater

C. estuaries contain both saltwater and freshwater

D. estuaries contain river water and freshwater

4. Which of the following BEST describes Chesapeake Bay?

A. the largest wetland in the United States

B. the largest estuary in the United States

C. the only estuary in the United States

D. the largest watershed in the United States



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The water within a watershed must have certain qualities to support life. Scientists monitor water sources over time to identify problems and improve water quality.

Virginia’s State Water Control Law exists to keep the quality of water in the state high, or healthy. To do so, scientists must monitor, or check on, water quality. They do some testing in the field with hand tools such as thermometers and water meters. Scientists also collect water samples and analyze them in laboratories. Scientists use a variety of indicators to determine the health of a water source.

Temperature, dissolved oxygen, pH, and water clarity are physical indicators of water quality. A healthy water source has moderate to cool temperatures, high dissolved oxygen, low acidity, and clear water.

Aquatic organisms are organisms that live in water habitats. They get the oxygen they need from the water in which they live. Colder water can hold more dissolved oxygen than can warmer water. So dissolved oxygen levels are related to water temperature.

Measurements that show high water temperature or low dissolved oxygen are indicators of an unhealthy water source. As water temperature increases, dissolved oxygen levels decrease. This can cause stress to fish and other aquatic organisms. Stressed organisms are more likely to become diseased. The low dissolved oxygen content in very warm water – temperatures above 29O C to 32O C – can cause fish kills. A fish kill is an event in which large numbers of fish die.

High or low pH readings are also signs of an unhealthy water source. pH measures how aquatic or how basic (alkaline) the water is. Neutral water has pH of 7.0. Most aquatic life does best in water at a neutral or slightly basic (8.0 to 9.0) pH. Some swamp organisms do well in more acidic water, with a pH from 3.0 to 5.0. Water may become too acidic (low pH) from acid rain. Water may become too alkaline (high pH) from an overgrowth of algae.