Watersheds, Soil Profiles, and Erosion

Grade Level

6 - 8

Purpose

Students develop an understanding of what factors impact water quality within watersheds, what soil types/profiles are most susceptible to erosion, and what factors impact water quality within watersheds and how to mitigate erosion on susceptible soils. Grades 6-8

Estimated Time

Three 45 minute activities

Materials Needed

Interest Approach:

Slide deck with aquatic ecosystem slides
Water samples
How Clean is the Water? student handout, 1 per student
Access to a computer or other device with wifi for possible research

Activity 1:

Understanding Watersheds slide deck
Driving Question Board slide
Understanding Watersheds student handout, 1 per student or per group

Activity 2:

Watersheds and Soil Profiles student handout, 1 copy per student or per group
Soil profile tubes and lids, 2-5 per group
- The profile tubes and lids, as well as the sand, silt, clay, and pea gravel, can be purchased from Lab Aids or Ward's Science.
Samples of sand, silt, clay, and pea gravel
Water
Timer
Cup to collect water
Graduated Cylinder
Calculator
Understanding Watersheds slide deck (optional)

Activity 3:

Watersheds and Erosion student handout, 1 per student or group
Painter’s tray and inside liners (You could also use aluminum paint containers but would need to poke small holes in one end of the pan to drain into a basin.)
Soil of various types (different combinations of sand, silt, and clay from local areas or createdwithin the classroom)
Potting soil (optional extension)
Gravel/rock
Plant material (optional extension)
Water
Small cup
Blocks or other source to adjust height levels of tray
Trash bag or other plastic table covering

Vocabulary

ecosystem: a biological community of living organisms interacting with the nonliving parts of their environment

erosion: the process by which the surface of the earth is worn away by the action of water, glaciers, winds, waves, and other natural forces

groundwater: precipitation that has infiltrated through soil, rock, and gravel in the ground

runoff: the draining away of water from the surface of an area of land

watershed: a watershed is the area of land where all of the water that falls in it and drains off of it goes into the same place

Background Agricultural Connections

Natural and human activities have altered the landscape and quality of many ecosystems around the world, including aquatic ecosystems. There is no single measure that constitutes good water quality. Water health is defined in terms of the chemical, physical, and biological content of the water. The health of aquatic ecosystems changes with the seasons and geographic areas, even when there is no pollution present. Precipitation dissolves or entraps dust and gases in the air to reach the earth's surface and flow over and through the soil and rocks, dissolving and picking up other substances. Human activities such as mining, forestry, urbanization, and agriculture have altered the landscape and quality of aquatic ecosystems. For example, industrial activities can increase concentrations of metals and toxic chemicals, increase temperature, and lower dissolved oxygen in the water. Agriculture can increase the concentration of nutrients, pesticides, and suspended sediments. Urban living has increased the runoff of debris and increased the concentrations of nutrients, pathogens, oil products, and road salts. A healthy aquatic ecosystem is one in which the water quality supports a rich and diverse community of organisms. The interrelationships between climate change, human activities, changing watershed conditions, and water quality can quickly make the balance shift, causing a change in the composition of the ecosystem.

We can’t speak about water ecology without including discussions on erosion, watersheds, climate change, and human activities, such as construction and development, impermeable surfaces, and agriculture. In this set of activities, we will be examining a large watershed, the mighty Mississippi River, and human impacts to the localized regional waterways and to the Gulf of Mexico. Students will learn about watersheds, areas of land that funnel drainage water into a water system such as a river, stream, lake, or ocean, and the watershed boundaries that divide them. Water flow is governed by gravity, not directionality, therefore all water runs downhill. Runoff commonly refers to the drainage of water from a land surface, be that a yard, a parking lot, roads, a farm field, feedlot, or other surface. When water runs off of a land surface, many materials may be picked up and moved with the water. This action is called erosion. Erosion might be due to water, or wind or glaciers. Water erosion can be of many types depending on the quantity of water running off and the elevation.

The water cycle incorporates surface water, groundwater, and water in the atmosphere. Surface water is what we see in lakes, rivers, streams, and the ocean. Groundwater is stored in aquifers that provide underground water for drinking and it may feed surface water sources. Precipitation recharges aquifers. The hydrologic cycle is constantly recycling water through the processes of precipitation, evaporation, and condensation.

Water flow is governed by gravity, not directionality, therefore all water runs downhill. Runoff commonly refers to the drainage of water from a land surface, be that a yard, a parking lot, roads, a farm field, feedlot, or other surface. When water runs off of a land surface, many materials may be picked up and moved with the water. This action is called erosion. Erosion
might be due to water, or wind or glaciers. Water erosion can be of many types depending on the quantity of water running off and the elevation.

The water cycle incorporates surface water, groundwater, and water in the atmosphere. Surface water is what we see in lakes, rivers, streams, and the ocean. Groundwater is stored in aquifers that provide underground water for drinking and it may feed surface water sources. Precipitation recharges aquifers. The hydrologic cycle is constantly recycling water through the processes of precipitation, evaporation, and condensation.

Many practices can help prevent erosion. Keeping the ground planted with plants, trees, or shrubs will allow roots to hold soil in place. Avoiding tillage or plowing the ground before planting or after harvest will allow the soil to retain its structure and increase percolation of water into the ground. Strip cropping and controlled grazing will also help. Students may do additional research to determine these practices and spend additional time to employ one or more of the strategies to hold their soil in place.

Engage

Give each student one copy of the How Clean is the Water? student handout.
Load the How clean is your water? slide deck to show your students and promote conversation about what clean water means. Ask these questions:
- Slide 1: Does this water seem clean? What factors about this image help you to decide it is clean or not clean?
- Slide 2: Is this water clean? How does this water compare to the first picture? What factors about this image help you to make your decision?
- Slide 3: Is this water clean? How does this water compare to the first two pictures? What factors about this image help you to make your decision?
- Slide 4: Is this water clean? How does this water compare to the first three pictures? What factors about this image help you to make your decision?
- Slide 4: Is this water clean? How does this water compare to the first four pictures? What factors about this image help you to make your decision?
Discuss as a class or in pairs to brainstorm ideas about water quality.
Refer to the teacher key to find options for differentiation in the classroom, answers to the reflection questions, and a rubric to evaluate the assessment.

Explore and Explain

Activity 1: Understanding Watersheds
How might we model a watershed? What are the impacts of various human activities on a watershed?

Use a Driving Question Board to help students focus on questions they would like to investigate.
- Refer to Science Storyline Design | Driving Question Board Strategy for an illustration of how to use a Driving Question Board in the classroom.
Show Driving Question Board slide. If students have trouble generating questions, here are some sample questions to get them started:
- How has human activity (construction, manufacturing, agriculture) contributed to runoff into streams, waterways, and other water sources?
- How have these activities contributed to acidity, nutrient enrichment, and turbidity in water?
- What organisms are most affected in regions where impacts are high?
- What needs to be done to improve water quality within watersheds, and how will this help to potentially improve the ecosystems in these bodies of water?
- Finally, what technology is available to aid agricultural producers to create a more sustainable means of food production?
Depending on the questions different groups decide to pursue, the following activities can be used to increase their knowledge and understanding of watersheds.
Show slide deck, Understanding Watersheds and Impacts on Ecosystems. This deck includes key terms that students may need to know. There is also background information on erosion, soils, nutrients and various aspects of watersheds to help students understand the impacts to watersheds.
Give each student or student group a copy of the Understanding Watersheds student handout along with a sheet of blank paper, markers, spray bottle, and tray described on the handout.
Instruct students to follow the instructions to complete the handout.
Refer to the Understanding Watersheds—Teacher Key to find options for differentiation in the classroom, answers to the reflection questions, and a rubric to evaluate the assessment.
Students should be able to summarize that a watershed is all of the land that drains into a water source. The human activities that take place within a watershed impact the health of the watershed.

Activity 2: Watersheds and Soil Profiles
What soils are most vulnerable to erosion?

Review the Driving Question Board from Activity 1 to help students address questions they would like to investigate.
Depending on the questions different groups decide to pursue, the following activities can be used to increase their knowledge and understanding of watersheds and their connection to soil texture and water percolation rate.
Draw on prior knowledge and review the following:
- How are soils formed?
- What are the three sizes of sediment that make up soils? (Sand, silt, and clay.)
- What is the difference between runoff and groundwater?
- What are different types of erosion and how do they impact water systems?
- What is a soil profile? (Soil Profile and Soil Horizons)
- What is soil percolation? (movement of water through soil)
Give each student one copy of the Watersheds and Soil Profiles student handout and the lab supplies listed on the handout.
Instruct students to follow the instructions on the handout. Introduce the purpose of the activity by explaining that some soils are better in helping to prevent erosion and excess runoff during certain weather conditions. They will be learning how water moves through various soil types, providing them with the understanding as to what soils run the highest risk of extensive runoff.
Refer to the Watersheds and Soil Profiles—Teacher Key to find options for differentiation in the classroom, answers to the reflection questions, and a rubric to evaluate the assessment.
Students should be able to summarize that erosion is dependent on slope. There are land management practices that may be used to lessen erosion on slopes.

Activity 3: Watersheds and Erosion
What is the impact of water on land surfaces? How might we prevent erosion impacts?

Revisit the Driving Question Board to address progress and clarify findings.
Give each student or group of students a copy of the Watersheds and Erosion student handout and provide access to the lab materials.
Instruct students to follow the instructions on the handout to complete the activity.
Once students have completed part 1 of the investigation, they will need time to research before determining which practice they want to experiment with for part 2.
Once they have determined which practice they want to investigate, additional time may be needed for them to grow plants or test out their hypotheses.
Students will create their own watershed as set forth in the activity. It will allow them to understand how erosion and runoff occurs and how they impact watersheds. It will also help them see ways in which runoff can be reduced. Instructors may choose to have students use a stream kit from a science company such as Wards or Lab Aids. The sand, silt, clay, and pea gravel can also be purchased from these same providers or a local home improvement store.
Refer to the Watersheds and Erosion—Teacher Key to find options for differentiation in the classroom, answers to the reflection questions, and a rubric to evaluate the assessment.
Students should be able to summarize that erosion is dependent on slope. There are land management practices that may be used to lessen erosion on slopes.

Concept Elaboration and Evaluation

After completing these activities, review and summarize the following key concepts:

A watershed is an area of land where precipitation collects and drains into a common outlet.
The human activities that take place within a watershed impact the health of the watershed. Converting natural ecosystems to agricultural ecosystems requires careful management to avoid negative impacts.
Soil texture and percolation rates impact runoff and erosion.
Erosion is dependent on slope. Land management practices can lessen erosion on slopes.

Elaborate

Have students play the Water Savers board game.

Evaluate

After completing these activities, students should be able to summarize the following key concepts:

Converting a natural ecosystem to an agricultural ecosystem requires careful management to avoid polluting local watersheds.
Soil nutrients in excess can impact local watersheds around farms.
Aquatic ecosystems include a variety of biotic factors including macroinvertebrates, plants, and other living organisms.

Sources

This activity is an excerpt of the Water Quality unit created by Nourish the Future.