LESSON
CREATE YOUR OWN HYDROGRAPH FROM STREAMFLOW DATA
OBJECTIVES
Students will be able to create a hydrograph from streamflow data using
Microsoft Excel. They will understand how to select segments of data, alter
elements of the graph, recognize patterns of flow (annual, daily), and compare
flows between streams.
METHODS
Students use Excel to select data and create graphs of flow over time.
MATERIALS
o Access to Microsoft Excel
o Morrell Creek flow data in Excel worksheet
o Access to the internet (for obtaining additional data on
streamflows)
o Instructor and Student pages from the end of this lesson
o Building a Morrell Creek Hydrograph PowerPoint (optional)
BACKGROUND
Grade level: 9-12
Subject Areas:
Biology, Earth
Science, Physics
Duration: 1 class
period
Setting:
Classroom
A hydrograph is a graph showing the rate of flow (discharge) versus
time past a specific point in a river or other channel. Discharge is generally
measured in cubic feet per second (cfs) or cubic meters per second (cms or
cumecs), and is represented by the symbol Q. Q = A * v, where A= area of the
stream and v = velocity. Hydrographs can show daily, monthly, or annual flows,
as well as changes due to storms or other discrete inputs of water.
In this lesson we’ll construct simple hydrographs in Excel, using streamflow data
collected on Morrell Creek in Seeley Lake, Montana.
PROCEDURE
Have your students go through the process of building a Morrell Creek
hydrograph in class. You may want to go through the procedure yourself using
the projector so they can make sure they are on track, or use the PowerPoint
slides for this purpose.
STUDENT PAGES
Build a Morrell Creek Hydrograph
1. Open the Microsoft Excel file Morrell Creek Data. You will see a table
with rows running across the page and columns running up and down the
page. Each box is known as a cell. The first row has labels for each
column.
2. Your first step in building your graph will be to select the data you want
to use. For this graph, your variables are date/time and discharge, or flow.
Which of these is the independent variable and which is the dependent
variable? Why? Which should be on the x-axis and which should be on
the y-axis?
3. To select the data cells you’ll use in
your graph, it’s easiest to just select
the A and B columns. To do this, put
your cursor over the blue box labeled
A above the first column. The blue
box should turn yellow. Left click on
this and, holding down, drag your
cursor over to the next box labeled B.
This should highlight both columns in
blue, as in this screenshot:
4. Now click on the Insert tab at the top
of the page, then on the box labeled
Scatter below and to the right. From
the drop-down menu that appears, put your cursor over the box in the
second row down and the second column over. A pop-up box should say
Scatter with Straight Lines and Markers (see below). Left click and your
graph should appear in your spreadsheet.
5. Your graph will
look something like
this. You’ll want to
stretch your graph
out to be able to see
the details better.
Grab a corner of the
graph and stretch it
out until you can see individual dates along the x-axis. You may want to
stretch it quite a bit, until your graph takes up most of your screen.
6. Use your graph to answer the following:
a.
Why are some of the points on your graph spread out and
others clumped very closely together? (You may want to
scroll through the data cells to get more information).
b.
At what date and time was the highest flow recorded?
(Hint: you can put your cursor over any data point on the
graph and a pop-up box will give you information for that
point. Just don’t click on the point or line or this won’t
work.) What was the discharge at that point in Morrell
Creek on that date?
c.
When was the lowest flow recorded and what was it?
d.
Describe the overall trend(s) in annual flow do you see in
Morrell Creek.
7. Now you’ll create another graph, using only a portion of the data you
used for the first one. Scroll down the A and B columns until you reach
the date 6/23/2012. Beginning with that record, select the cells in both
columns A and B down to the last record for 6/28/2012. Then follow the
same procedure you used to create the first graph. You should end up
with a graph of the data for just those dates. Use it to answer these
questions:
a.
What trend(s) do you see in the data for these 5 days?
Describe the overall trend and any daily trend or pattern
you see.
b.
What do you think causes the pattern in daily flows that
shows up in your hydrograph? What time of day is the flow
highest and when is it lowest? Why?
8. Repeat this with the data for dates 7/1/2012 through 7/12/2012.
a.
What do you see now? Are there daily patterns in flow? If
so, do they differ from those of the June dates? If so, how?
What do you think might explain any differences you see?
9. What percentage of the total flow in the Blackfoot River do you think
Morrell Creek contributes? How can you determine this? (Check out the
streamflow data for the Blackfoot River at Bonner at
http://waterdata.usgs.gov/mt/nwis/uv?site_no=12340000. Select dates to
compare discharge in the Blackfoot to those in Morrell Creek.
a.
What do you find? Do you think all the water in Morrell
Creek makes it to the Blackfoot at Bonner? Why or why not?