Activity: Stream table use for exploring water erosion and deposition, by Ellen DeBacker

Overview

These activities focus on the water cycle, erosion and deposition, and watersheds and aquifers. The stream table allows students to experiment with stream processes in the classroom environment that normally can only be observed in the field.

Purpose and learning goals

To help students visualize and experiment with variables that affect streams, watersheds, aquifers, mass wasting, and glaciation.

Intended grade level

8th grade

Time involved

Preparation time: 1 hour to set up an existing stream table and gather supplies
Student time: 10 to 15 minutes for each sub-activity

Alignment to National Science Education Standards (5-8)

Unifying Concepts and Processes: Evidence, models, and explanation; and Change, constancy, and measurement
Science as Inquiry: Abilities necessary to do scientific inquiry
Science and Technology: Understandings about science and technology
Earth Science: Structure of the earth system

Background information for the unit

Stream tables are available for purchase, but can be quite expensive. The Boulder Valley Soil Conservation District, Longmont, CO has a stream table that can be borrowed by teachers in the Boulder Valley and St. Vrain school districts. Other soil conservation districts may have funds to help purchase a unit. Stream tables can also be created out of a bin, sand, and a water source such as a hose or squirt bottle.

Knowledge of landforms, soil, water, and erosion is important to the success of these activities.

Materials

Stream table
Nylon netting pieces
Small river rocks
Popsicle sticks
Small model pine trees
Watering can
Labels on sticks

Preparation

Obtain the materials. Be sure that the stream table is operating properly. Some of the subactivities require setting up a scenario prior to use, others are done as the activity progresses.

Subactivities

Streams as part of the water cycle

Introduce the rules of the stream table. For example, no water or sand outside the table, no splashing, washing hands before and after use, and keeping sand away from the outlet.
Show students how the stream table works. Include modeling a landscape, turning on the water, and observing the movement of sand particles at the edges of the streams.
Allow students to experiment with the stream table and various landforms, stream configurations, and water flows.
Discuss as a group or in writing what was observed and what other trials could be explored with the stream table.

Healthy watersheds demonstration

Give the students information about watersheds and how they operate.
Create two hills in the sand with a valley in between that could have a stream. Turn the water off for this demonstration.
Sprinkle the hills with water to show that the runoff goes into the stream. This illustrates that the watershed is the land that collects the water from rainfall, with the stream being the overflow. Also observe the amount of soil that runs off the hills during the rainfall.
Reshape the hills if necessary. Place a piece of netting over one hill. The netting illustrates roots or grass on the hill. Sprinkle with water. Observe the decrease in soil runoff when roots help to hold the soil in place.
Reshape the hills if necessary. Place small model pine trees on the hill. These can be on top of the netting or separate. Sprinkle with water. Observe the decrease in soil runoff when trees slow the fall of water to the soil.
Reshape the hills if necessary. Remove the trees to simulate a fire or clear cutting situation. Sprinkle with water. Observe the increase in soil runoff when trees have been removed.
Reshape the hills if necessary. Place popsicle sticks along the contours of the hill to simulate reclamation work on the hills after a fire. (Fire crews place tubes stuffed with straw along the contour lines to slow the flow of water and soil runoff after a fire.) Sprinkle with water. Observe the decrease in soil runoff when reclamation work is done.
Demonstrate other variations of watershed/land management as desired.
Discuss what was observed in terms of watershed management and health, including the ethics, politics, and values of management decisions.
Discuss the use of models, how they can be great visualizations of systems, and how they can exaggerate or under-represent portions of a system.
Point out or ask about the size of watersheds - that they can be very large (for example, all of the land over which the Mississippi River and its outflow flow)

Aquifer demonstration

Dig into the sand. Water from the ground water will fill the hole to the level of water in the lake. This illustrates that water is underground within the pores of the rock/soil and not in an underground lake.
Discuss how the water moves through the pores of sand to fill up the hole through capillary action and gravity.

Mass wasting inquiry

Have groups of students use the stream table to explore mass wasting by creating a mountain and then sprinkling water and observing the landslides.
Ideas:
- Create mountains of different heights.
- Sprinkle water for different amounts of time.
- Time the sprinkling process from start to slide.
- Measure the extent of landslide compared to height or rainfall.

Glaciation

Create a model landscape in the sand with mountains, cirques, horns, arêtes, terminal and lateral moraines, and u-shaped valleys. Label each landform with a toothpick flag that has a letter on it.
Allow students to identify each formation on the model.

Glaciation in action

Freeze cubes of ice that have sand or gravel in the water. Allow groups of student to do this or use it as a demonstration.
Use the ice cube to represent a glacier. Move it downhill. Observe the moraines that form and the u-shaped valley. Let the ice cube sit and thaw. Observe the cirque or kettle lake (depending on location) and pile of debris.

Reflecting on the activity/ideas for assessment

These are just 6 examples of how a stream table can enrich instruction about soil, water and erosion. Assessment could done by having students demonstrate a concept in the stream table or by writing about what was discovered at the stream table as examples to illustrate the concept.

Key questions that may be asked with 'Look fors'

What was observed at the bends of the streams for erosion and deposition? (Erosion on the outside curve, deposition on the inside curve)
What was observed where the stream hit the lake or ocean? (Deltas or alluvial fans)
How does the riverbed change as it travels over steeper and flatter terrain? (Digs deeper and stays straight on steep ground, meanders over flatter terrain)
Talk about the health of watersheds, bringing in the ethics of land use.
What is the relationship between the angle of the mountain, rainfall, and landslides?
How does slope effect erosion? (Steeper slopes have increased erosion)
Should building permits be allowed for structures in steep slope areas? (Ethics and safety issues)
Review the erosion and deposition of glaciers by asking students to explain how each glacial feature fits either erosion or deposition. (Moraines would be deposition, u-shaped valleys would be erosion)

Extensions and applications

Have students look for examples of streams, water flow, and water deposition and erosion in their neighborhoods and surrounding landscapes.
Have students do a role-play of the different issues and sides involved in watershed management.
Have students research the Ogallala Aquifer that supplies water to a large portion of the mid-west United States.
Have students identify slopes that are prone to mass wasting erosion in their neighborhoods.
Take the students to a national park that has been impacted by glaciation.
Ask a soil scientist or hydrologist to speak about what they do.
Ask a city manager or water supply manager to speak about water issues in the community.
Create artwork about water, soil and erosion.
Research the Dust Bowl of the 1930's.

Adaptations for special needs

Perhaps a stool or modified seating to allow all students to reach the stream table.

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