BY SARAH J. FICK AND JONATHAN BAEK
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CONTENT AREA
Earth and space sciences
GRADE LEVEL
6–8
BIG IDEA/UNIT
Earth’s systems.
ESSENTIAL PRE-EXISTING
KNOWLEDGE
Basic water cycle
processes and vocabulary
Gravity and forces
Map navigation and
symbols
Measurement skills and
tools
Helpful: Energy (kinetic
potential, and thermal)
TIME REQUIRED
Varies, depending on
which activities you
implement. Eight class
periods of instruction are
described.
COST
Varies, depending
on which activities
you implement. Each
activity can be modified
according to the
resources available.
F e b r u a r y 2 0 17
25
A
s part of a middle school unit on the flow of
water on and through the Earth’s surface, students use multiple models to represent the
factors that influence water flow within watersheds.
This article shows how the unit incorporates a variety of tools (including models and digital and paper
maps) to help students make sense of the content using a variety of data sources. The unit also encourages students to have a more flexible understanding
of the concept of water flow. In this article, the word
model is used to mean any simplified representation
of the landscape. In these activities, a model can be
a topographic map, an online map, a digital elevation model, or a physical representation. The term
conceptual model is intended to mean students’ drawings of their current understanding of the system.
One of the key components of the unit is the use of
conceptual models periodically throughout to gauge
students’ understandings. Conceptual models are
based on student understanding and are expected
to become more sophisticated over time. As students
learn additional information about watersheds and
the movement of water, they are asked to draw a new
conceptual model representing their understanding.
These conceptual models show the progression of
students’ ideas during the unit, and can be used by
the teacher to support students by illustrating their
changing understanding and highlighting any areas
of confusion.
One challenging but key component is supporting student understanding of how elevation combined with the force of gravity influences the flow of
water. Students are often familiar with the fact that
water flows “down,” but understanding the presence of subtle elevation changes in the larger landscape is not easy for many students. One of the goals
of the unit is to help students understand the influence of elevation changes, large and small, on the
flow of water. Students often think that areas with
less elevation change are “flat,” and as a result, the
water does not travel. Students in North America
often also hold misconceptions about the direction
of water flow. For example, they may believe that
all rivers flow south or water gets absorbed by the
ground and doesn’t travel. These statements are not
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Materials for experience 1
• 1 8–12 oz. piece of modeling clay/play dough
per group
• 2 meter sticks per group
• 1 wire clay cutters per group
Total cost: Approximately $11.75/group ($10.50
per group is reusable; might need to buy replacement modeling clay/play dough)
always false, but over-application to inappropriate
situations leads to misconceptions. In our experience, students often hold these misconceptions and
watershed-specific misconceptions (e.g., watersheds
only consist of bodies of water, not the land that surrounds them; watersheds are sheds that hold water).
Description of activities
One of the primary goals for the beginning activities
is for students to understand how the water cycle
interacts with the Earth and to connect students’
knowledge of their local geographic context to the
|FIGURE 1: ESRI terrain profile tool output
The ESRI terrain profile tool allows you to trace a line
on a map with topographic data and translate that map
into an elevation profile.
SUPPORTING STUDENT UNDERSTANDING OF WATERSHEDS BY USING MULTIPLE MODELS TO EXPLORE ELEVATION
concepts of elevation and gravity. In the beginning
lessons, students revisit the concept of the water
cycle, which many students had learned the basics
of in earlier grades, and apply it specifically to the
state of Michigan. The beginning part of the unit
is framed around these questions: “What happens
when it rains in the state of Michigan? Where does
the water go?”
This article summarizes activities that helps middle school students understand the flow of water on
and through the Earth’s surface. We suggest providing students with an initial formative assessment,
such as the one described in this article, to determine
which of these activities might give your students a
more thorough understanding of a watershed system and the energy that drives the movement of water. Differences in school context and student experience might mean that your students have a different
grasp of elevation and how it is represented or how
slope dictates the flow of water.
Engage: ESRI digital elevation tools
(one class period; 50–60 minutes)
To begin the unit, students examine their local environment. Focusing on Michigan at a state level, we
examine how water moves on the surface at a broader scale. It is our intention that this initial activity engages students’ prior knowledge and understanding
by exploring a familiar area. Students use the terrain
profile tool in the ESRI web GIS platform to view the
elevation along the length of a river (see the lesson
description for full directions; see Resources for a
link to the online tool). The web version of the ESRI
software does not require any specialized software
and can be used on any device with internet access,
although use of the tools may be easier on a computer than a tablet. The terrain profile tool allows you to
create a line segment that can follow any geographical feature. In this case, we draw a line that follows a
river (Figure 1). This allows students to observe the
slow decrease in elevation as the river makes its way
to the destination. Determining the flow of a river is
not intuitive for all students. In the first iteration of
the unit, we had students predicting that the desti-
nation of a stream was actually the headwaters that
formed the stream because the headwaters were
south of the destination of the river. This is just one
example of how students’ misconceptions about the
flow of water might play out in a data analysis activity. Unless students are shown evidence that the process is not feasible, they sometimes have a hard time
overcoming their belief in prior knowledge.
After the teacher demonstrates following one
river together as a whole class, students are free to
explore a different river on their own. In table groups
(3–5 students per table), students are assigned wellknown rivers around the whole state, and use the
search features described in the ESRI tool to zoom
into that area. In this activity, students make predictions about the direction of flow based on the map,
and then check their predictions by looking at the
elevation profile for the river. After each group examines their river, students highlight their river on a
state map projected on the whiteboard and indicate
the direction of flow of the river they examined. Observing the trends in the rivers overall allows for a
class discussion that focuses on themes in how the
rivers move. While this activity helps students see
the relationship between elevation and water flow,
students are focused on the bodies of water themselves, not the land that drains to the body of water.
For students to understand how water gets to bodies of water within a watershed, we need to support
their understanding of how elevation is represented
in various types of models. To do this, students create
a model landscape and its related topographic map.
Experience #1: Modeling elevation
using physical models (two class
periods; 100–120 min.)
Students often have a difficult time understanding
what topographic lines represent. To help students
see precisely what an individual topographic line
represents, we have them create a 3-D model of a
mountain out of clay (or play dough) and then we
physically convert that mountain into a 2-D representation, creating the topographic map for that
mountain. The activity begins with a basic clay mod-
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slice onto paper, making sure to align the segment
according to the cardinal grid that was originally
drawn. As students remove each layer, they produce a topographic map (Figure 2). The steep side
and the gradual side of the clay mountains illustrate
for students how differences in slope are represented
using a topographic map. Variations of this activity
can also include adding watershed features (rivers,
lakes) to students’ clay mountain and observing
how those features are represented in the contours,
as well as changing the contour interval to increase
or decrease the height at which you slice the layer.
Students compare the created 2-D topographic
map to the 3-D clay model to see evidence of how differences in elevation changes are represented on the
topographic map (Figure 3). Students are also asked
to show how water would flow on their mountain.
This information is represented using arrows on the
topographic map of their mountain (Figure 3). When
students can easily identify which areas are steep or
which direction a river flows from the contour lines,
it allows students to work with a greater variety of
data types to analyze the watershed boundaries and
how water moves in a geographic area. Students can
also apply these concepts to interpreting topographic maps of
other locations.
FIGURE 2: A sliced modeling clay mountain next to its
el of a single peaked mountain, with a steep side and
a more gradual side. Students work in small groups
(3–5) at tables with a small bag of modeling clay (8–
12 ounces) and are given initial instructions to shape
the mountain. For safety, it is recommended that
students wear goggles while working with the PlayDoh or clay models and wash their hands afterward.
Next, so as to provide proper alignment of the
mountain during the activity, students are instructed
to create a cardinal grid by carefully imprinting the
clay with a pencil for North-South/West-East perpendicular dotted lines, as well as extending and
drawing it on the paper. After students design their
mountains, they segment the mountain into slices
of equal height using wire clay cutters (a thin piece
of wire used for slicing clay, but not sharp for students). Two meter sticks, lying flat on either side of
the mountain, provide a consistent height (~ 1 cm)
for the wire cutters to follow as it slices through the
clay. A firm side-to-side motion, while pulling from
the farthest side inward toward the student, works
best to create consistent slices. Students continue this
until the mountain is completely segmented. After
students slice each piece, they trace the outline of the
|
topographic map
Here, the slices are laid out next to one another with the topographic map
constructed using an outline of the different layers.
Experience #2:
Paper topographic
maps
(two class periods;
100–120 min.)
Topographic maps of a local
area can help students identify
major factors that influence how
water will flow in that area. To
support students in making and
checking predictions about the
flow of water on the surface of
the Earth, we print several topographic maps (available through
the USGS map service; see Re-
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SUPPORTING STUDENT UNDERSTANDING OF WATERSHEDS BY USING MULTIPLE MODELS TO EXPLORE ELEVATION
|FIGURE 3: Clay mountain with topographic
|FIGURE 4: A laminated topographic map
The equal height slices of the modeling clay mountain
are shown next to the corresponding topographic
map. The topographic map has arrows on it showing
students’ predictions about the direction of water flow
on this mountain.
On the annotated map, the class designated
mountainous areas with inverse Vs, and then predicted
the direction of the water flow. Finally, the map includes
lines that show that higher elevation divides the flow of
water.
map
sources) and laminate them to make them reusable,
allowing students to mark the maps with dry-erase
pens (Figure 4). We choose a local river and ask students to find different points of elevation (e.g., lowest, highest, greatest slope change, gradual changes)
and then ask which direction water will flow from
any spot the teacher identifies on the map. Because
students are already familiar with topographic lines
and how they can indicate which direction water
flows (the rule of inverse Vs: When there is a V in a
with water flow predictions
topographic line with a river in the center of the V,
the V will generally point uphill), we ask them to
identify on the map some instances where these indicators could be seen, and as an efficient formative
assessment, we have them circle an example on the
map and indicate the direction of water flow.
Experience #3:
Digital topographic maps
(one class period; 50–60 min.)
ArcGIS Online also has other tools that students
can use to analyze the hydrology of an area. One of
these tools is a wide variety of map layers available
within the user community. We found several hy-
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|FIGURE 5: A Digital Elevation Model
A Digital Elevation Model (DEM) can use colors to show
which areas of the landscape have higher and lower
elevation relative to the surrounding areas.
|FIGURE 6: A student’s final conceptual
model of a watershed
This model focuses more closely on the aspects of a
watershed that closely align with systems. The student
shows a watershed boundary, which incorporates many
smaller bodies of water and the land that surrounds
them. Written words show the areas of higher and lower
elevation in this model.
drology layers for the state of Michigan, with varying amounts of detail. There was one statewide layer
that also included local streams, which seemed like it
would support students’ learning. We would recommend that you search within ESRI’s data layers for a
hydrology layer for your own state. A key crosscutting concept that is important for supporting student
learning is that watersheds are systems. The various
components of this crosscutting concept (inputs, outputs, boundaries, nested systems, and interactions)
can be illustrated by using ArcGIS as well as other
online resources such as topographic-map.com (see Resources), which allows the user to see topographic
data using different display techniques. (See also
Fick, Arias, and Baek, forthcoming.)
Within ArcGIS Online, there are multiple map
layers that can outline established watershed boundaries, highlight hydrological features, and provide
tools to measure and mark on the map. Our students
first research a local creek, where we use ArcGIS to
help identify and outline the tributaries and the areas of land that feed into those bodies of water. From
this, students identify the output of the local creek
and make connections to how it also contributes to
the larger Huron River watershed basin. The concept of nested systems, a set of smaller systems that
together form a larger system, becomes more accessible when students can trace where the Huron River
feeds into Lake Erie at the output of the river, and
how that body of water connects to others, eventually reaching the ocean.
Elaborate: Digital elevation models
(two class periods; 100–120 min.)
As part of a summative synthesizing project, students apply what they learned about the local area
to a different area anywhere in the world. Students
are given the freedom to choose any geographic
area that interests them, and they use the tools
we used in class to analyze the topography. These
tools, as well as the digital elevation model (DEM)
available on topographic-map.com, help students develop an understanding of how water moves on the
surface of the Earth in less familiar environments;
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SUPPORTING STUDENT UNDERSTANDING OF WATERSHEDS BY USING MULTIPLE MODELS TO EXPLORE ELEVATION
students eventually create a report about a watershed in that region. Students are assessed on being
able to identify components of watersheds (boundaries, inputs, outputs, interactions), as well as the
quality of their created model. A rubric is provided
for students to understand all of the objectives required (see the rubric in the Online Supplemental
Materials). DEMs use detailed elevation informa-
Connecting to the Next Generation Science Standards (NGSS Lead States 2013)
• The chart below makes one set of connections between the instruction outlined in this article and the NGSS. Other valid
connections are likely; however, space restrictions prevent us from listing all possibilities.
• The materials, lessons, and activities outlined in the article are just one step toward reaching the performance expectations
listed below.
Standards
MS-ESS2.4: Earth’s Systems
www.nextgenscience.org/pe/ms-ess2-4-earths-systems
Performance Expectations
MS-ESS2.4: Develop a model to describe the cycling of water through Earth’s systems driven by energy from the sun and the force
of gravity.
DIMENSIONS
CLASSROOM CONNECTIONS
Science and Engineering Practices
Analyzing and Interpreting Data
Developing and Using Models
Students use topographic maps and digital models of
elevation to determine the slope of the landscape and then
use that information to predict the direction of the flow of
water.
Students create conceptual models to show their
understanding of the watersheds and the flow of water
through a landscape.
Disciplinary Core Ideas
ESS2.C. The Role of Water in Earth’s Surface Processes
• Water continually cycles among land, ocean, and
atmosphere via transpiration, evaporation, condensation
and crystallization, and precipitation, as well as downhill
flows on land.
Students use models of elevation to predict the flow of water
based on knowledge of the downhill flow of water caused by
the force of gravity pulling the water down the slope of the
landscape.
• Global movements of water and its changes in form are
propelled by sunlight and gravity.
Crosscutting Concept
Systems and System Models
Students determine the boundary, inputs, outputs,
processes, and nested systems for a particular watershed,
and draw conceptual models identifying the components of
the watershed.
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SUPPORTING STUDENT UNDERSTANDING OF WATERSHEDS BY USING MULTIPLE MODELS TO EXPLORE ELEVATION
tion to create a layer of elevation where every pixel
or point (depending on the data used to make the
data layer) is assigned an average elevation for that
area. These data can then be represented using a
color gradient to show the elevation for each location as a color, making it easy to identify higher and
lower elevation locations (Figure 5). The DEM helps
students quickly visualize the elevation changes for
the geographic area they select. The color gradients
help students see changes in elevation and provide
a clearer visualization for students to use in order to
convert 2-D maps that are available for their locations into the 3-D model that they have to create for
their project. The resource also allows users to click
on a specific location and provides the elevation for
that location, which helps to determine the direction
of water flow.
Evaluate: Understanding student
learning (incorporated into lessons
throughout the unit)
Throughout the activities, students are asked to draw
what a watershed looks like. Similar prompts are
used throughout the unit, and students are prompted to think about how their current drawing is similar to and/or different from their previous drawing.
Students’ drawings slowly evolve over time to incorporate some of the elements being described in class.
At the end of the unit, students are asked to complete one final drawing showing their understanding of a watershed for a unit test. Figure 6 shows an
example of student work at the end of the unit. This
image show students’ final understanding from the
unit. In this conceptual model, you can see students
representing movement of water on and through the
surface of the Earth, with elevation and sometimes
gravity pulling the water downhill or into the layers
of the Earth’s surface. The image shows the boundary of the watershed existing in areas with higher
elevation, and sometimes watersheds nested within
other watersheds. Students represent the areas of
higher elevation through various methods, including labels, side profile drawings, and inverse Vs. All
of these means of representing the concept contribute to a thorough representation of the content when
used with labels of water flow and other representations. See the Online Supplemental Materials for a
rubric to evaluate students’ models.
This article shows how the use of a variety of models requires students to make sense of the same concept using a variety of data sources. Students are able
to use digital and analog resources to make sense of
the same content. We found that it is important for
students to see multiple modeled representations of
elevation to fully understand how elevation influences the ways that water moves on and through the
surface of the Earth due to the force of gravity.
•
REFERENCES
Fick, S., A.M. Arias, and J. Baek. Forthcoming. Unit planning
using the crosscutting concepts. Science Scope.
NGSS Lead States. 2013. Next Generation Science Standards:
For states, by states. Washington, DC: National Academies
Press. www.nextgenscience.org/next-generation-sciencestandards.
RESOURCES
ESRI Terrain Profile Tool—esriurl.com/elevation
Free US K–12 Educational Accounts—www.esri.com/
connected
United States Geological Survey (USGS) store—store.usgs.gov
(select local topo quads in 7.5’ x 7.5’ scale)
USGS topographical maps—www.topographic-map.com
ONLINE SUPPLEMENTAL FILES
Rubric for evaluating students’ watershed drawings—www.
nsta.org/scope1702
Watershed project rubric—www.nsta.org/scope1702
Worksheet one: ESRI digital elevation tools—www.nsta.org/
scope1702
Worksheet two: Creating a clay model—www.nsta.org/
scope1702
Sarah J. Fick ([email protected]) is an assistant professor of science education in the Department of Education at Wake Forest
University in Winston-Salem, North Carolina. Jonathan Baek is a middle school science teacher at Honey Creek Community
School in Ann Arbor, Michigan.
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