Where Does Stream Water Come From?

Christa Torrens, Flathead Lake Biological Station, University of Montana

Author Profile


Rivers are an important natural and sociopolitical resource, and their benefits (ecologically, recreationally, as a water source, hydropower generator, and more) depend on protecting water quality AND quantity. To protect these effectively, it is important to understand where the stream water is coming from: what the streamwater sources are at any given time, and how and when these change. Protecting the sources is key to protecting the stream.

In this module, students explore various sources of stream water through reading, discussion, and data analysis in R. The module focuses on streams from four distinct LTER sites: an Antarctic desert stream, an Arizona desert stream, an Arctic tundra stream, and a temperate forest stream in New England.

Used this activity? Share your experiences and modifications

Learning Goals

By the end of this module, students should be able to:

  • Describe what a hydrograph is, and why they are useful resource management tools
  • Interpret different hydrographs: how different water sources can impact the shape of a hydrograph
  • Work with large datasets in R: exploring, visualizing, and analyzing data in R
  • Assess how streamflow is generated in various LTER biomes, including how (and whether!) groundwater plays a role in this
  • Describe the diversity of biomes and hydrology in LTER sites, and by extension, around the world

Context for Use

How Instructors Have Used This Module

Using Project EDDIE modules in Freshwater Biology
David Richardson, SUNY College at New Paltz
Determining the sources, temporal dynamics, and spatial differences in stream source water is a valuable exercise for general environmental science, geology, or biology students or students that are focusing on a water resource/aquatic ecology careers. This module helps students get exposed to a variety of streams outside of their local biome, hydrographs, working with R, and thinking about data!

This module is designed for:

  • Educational level: Undergraduates
    • Either with some knowledge of hydrology and R, or be willing to teach these in conjunction with the module [this will increase module teaching time]
  • Class size: 4 to 40+
  • Lab or lecture w/ computer access (unless all students have a laptop to work with); can work with R and R Studio installed on the computer (have this done ahead of time), or with RStudio Cloud
  • Time: 2.5-3 hours, plus time to work on any background materials; this could fit into 1 lab meeting or 2 shorter class times. Also, some of the work could be assigned as post-class homework.
  • Intended use: an intro course on hydrology, groundwater-surfacewater interactions, watershed or stream ecosystem processes, etc.
    • Could be modified to have some or all of the R labwork as homework
    • Could be modified for non-R audiences by removing the student R work and just presenting the info packets and (after the students sketch their hypotheses) hydrographs.

Overarching question related to the concept that will drive their investigation

How and why does streamflow vary in different biomes?

To answer this question, students/ student groups will select one of 4 different LTERs and stream systems; read about and discuss potential streamwater sources; plot and analyze a hydrograph from 'their' stream system (in R); and compare/ contrast their site's hydrograph and water sources with those from other LTER sites. Students will answer these sub-questions:

  • What does their site's hydrograph look like, and why (e.g. what water sources are contributing to the year-long hydrograph)?
  • How do the water sources, and therefore streamflow, change through the course of the year?
  • How does their LTER site compare with other sites: how are the hydrographs and water sources similar, different, and why - e.g. what site factors impact each hydrograph and how do these compare across sites?
  • What additional information or data could they use to support their ideas regarding the hydrograph and streamwater sources at their site? Where could they find this information?

(students will need to know or learn some basic hydrology terms: groundwater, hyporheic zone, runoff, watershed)

Description and Teaching Materials

Quick overview of the activities in this module

Activity A: Pre-class

  • If applicable, students load R and R Studio onto their laptops.
  • If instructors wish to provide their students with additional information about hydrology or other topics relating to this module, they can do this here.

Activity A: In class

  • Using the provided PPT, the Instructor provides background information on streamflow and hydrographs, then introduces the hands-on work. The PPT will include a sample hydrograph, and the instructor will guide a class discussion regarding factors that can impact the shape of a hydrograph (for the base PPT, the example will be the Wallkill River, showing a rain-related increase in flow. Instructors can swap this for any other stream; there is also the opportunity for instructors to add and interpret >1 different hydrographs to focus on, say, urban impacts).
  • Formative assessment: Students work in pairs or small groups; each group selects or is assigned one of the four LTER sites (ensure that all four sites are selected!). Using the site info packets as a reference and the worksheet (Q1) as a guide, student groups discuss then sketch what they think a hydrograph from their selected site would look like and explain why they drew it the way they did.
  • If needed (and this will extend the lesson time), the instructor gives a brief overview of R/ RStudio - with a screen-sharing demonstration from their computer - that includes an intro to the parts of RStudio, how to create and structure a working directory on their computer, how to open a file, and the basics of how to read an R script (including what comments are and how to benefit from them), and how to run one line of code at a time.  Ideally, this would happen earlier in the term, *before* this module is taught.
  • Students start working in R while the instructor walks around/ is available for help. Students can work together and help each other, AND *each student should work on their own script/ generate their own work* so that everyone gains experience using R.  
  • The instructor can use the 'red flag/ green flag' method, where students who have a question or are stuck put a red or orange sticky note 'flag' on their monitor, while students who are working quickly/ are willing to help others can put up a green sticky note indicating they are finished and perhaps available to help other students.   When all flags are green, the class is ready to move to the next step. 
  • Students create a working directory (see the "Getting Started" document for instructions), download their site's R script and streamflow dataset into this working directory, and plot their hydrograph.  The provided R script templates (with comments explaining each step) and worksheets guide the students as they explore the dataset and  plot the hydrograph for their site. 

Activity B: In class

  • Student groups discuss  their own site and what water sources or other factors might be causing the streamflow 'picture' they saw in the plotted hydrograph. The worksheet guides this discussion. 
  • Paired-group discussion: Answer the overarching question: How and why does streamflow vary in different biomes? 
    • Each group pairs with a group that analyzed a different hydrograph. 
    • Use the provided worksheet to guide discussion regarding the similarities and differences between the two hydrographs, and what factors (water sources, etc.) may be causing these differences. 

Activity C:  In class

  • Students re-focus on their own group and site, and explore the overarching question, focusing on streamwater sources at their site.
  •  Small group discussion of the plotted (data-driven) hydrographs vs. student hypotheses (initial sketches): how does the plotted hydrograph compare to their hypothesis?  If there are differences, what caused the differences? 
  • Students identify what they know about their hydrographs and water sources, and what they still don't know.
  • Then students discuss what types of data and analyses they would need to support their (revised) ideas or answer their questions regarding the water sources for each hydrograph (e.g. precipitation, PAR, temperature, snowmelt data).  How could they test whether these were impacting the hydrograph (e.g. by plotting them on the same graph?)? Would the impact be immediate or lagged (and if lagged, by how long?)?  Are these datasets available at their LTER site? Links to each LTER site are included in the site description packet.
  • Optional: Full-class comparison of all four hydrographs: Groups report back/ compare the hydrographs from all 4 sites and discuss how and why they are different - where is the water coming from in each case?

Activity D: In or Post-class

  • Optional: If students are familiar with R, they can select, download, and plot the supplemental information they identified in Activity C, to test their hypotheses regarding water sources, then discuss how these additional analyses did or did not match their predictions.  Potential data sources include their LTER site and the EDI website; links are in the 'References and Resources' section below. 
  • Students would need to understand how to find, download,  subset, and possibly clean these other datasets, as well as how to modify the template R script to work with the new dataset(s).
  • This can also be a post-class assignment

Activity E: In or Post-class

  • Optional: If students are familiar with R, have each student plot a hydrograph from a  stream or river of their choice: e.g. one that's local to the class OR one from their own hometown (USGS streamgage data is often a good data source for this), and analyze how it compares to the 4 sites from the module. Discuss: What is impacting the streamflow and hydrograph of their selected stream? How does the  hydrology of their selected stream compare to the 4 LTER sites?  
  • Students will need to understand how to download 1 year of USGS (or other) streamflow data and how to modify the template R script to work with the new dataset.
  • This can also be a post-class assignment.   

Workflow of this module (instructors can edit as needed):

  1. Pre-class work: 
    • Make sure R and RStudio are loaded and working on each computer that will be used (computer lab or student laptops). 
    • Optional info sheet provided
  2. In class: Instructor gives a brief PowerPoint presentation with background material. Discussion of any readings can be integrated into this presentation or done before.
  3. In class: Activity A: Hypothesis, R work for data exploration and hydrograph plotting
    • Students form pairs or small groups and select (or are assigned) one of the four sites
    • Students read the provided information packet and Q1 of the worksheet (both packets and worksheets can be online or printed)
    • Groups discuss and sketch what they think the hydrograph from their site will look like, and write down why (what they think is causing any increases / decreases/ flat parts of their sketched hydrograph); optional blank graphs are provided for this. 
    • Students work in R, using commented R scripts and the provided worksheets to explore their site's streamflow data and to create a hydrograph. Each student should do this to gain experience using R.
  4. In class: Activity B: Data analysis and site comparison
    • Students examine their plotted hydrograph and think about what might cause the varying streamflow levels at their site.
    • Groups pair with one other group that worked on a different site. Using the worksheet as a guide, the two groups try to answer the overarching question: the two groups compare their site hydrographs and discuss similarities/ differences, as well as underlying site conditions/ factors that may be causing these differences.
  5. In class: Activity C: Assessing and supporting their ideas 
    • Groups compare the data-generated hydrograph to their sketch, and discuss similarities/ differences and what might cause any differences.
    • Students identify what they know about their hydrograph and its water sources as well as what they don't yet know.
    • Students  discuss what additional datasets and analyses they would use to test their (revised) ideas regarding the water sources for each hydrograph, or to answer any outstanding questions, then see if those data are available at their LTER site. 
    • Optional: full-class sharing and discussion of all four sites and hydrographs
  6. Optional: Students download and plot the additional  datasets they selected in #5, then compare them to their site hydrograph. 
    • Does it look like their hypotheses regarding stream water drivers were correct? Why or why not?
    • Students need some proficiency in R to succeed at this: e.g. the ability to download, subset and clean datasets, and to modify the provided R script to work with this new dataset.  This activity is best for students who are familiar with R or who have a lot of technical (R) support for this assignment.
    • This can also be a post-class assignment.
  7. Optional: Students download data and plot a hydrograph from a stream or river of their choice.
    • Have students assess the water sources for their chosen stream, discuss how these sources  shape their hydrograph, and compare their hydrograph/ stream with the 4 LTER sites from the module. How and why is it like or unlike the different LTER sites? Is there a different LTER site that might be a closer match for their stream?
    • Again, students need some proficiency in R to succeed at this: e.g. the ability to download, subset and clean datasets, and to modify the provided R script to work with this new dataset.  This activity is best for students who are familiar with R or who have a lot of technical (R) support for this assignment.
    • USGS, EDI,  and NEON are good sources of streamflow data. Students can also select other streams from their LTER. 
    • This can also be a post-class assignment.

Teaching Materials:

  • Instructor - Introductory ppt. (both full-size and compressed versions: same information in each)

Introductory Powerpoint lecture [PPT] that covers basic background material: hydrological concepts (streamflow, what can contribute to streamflow), what a hydrograph is, what it tells us.  Includes a slide with an example hydrograph to discuss as a class (The pilot module uses the Wallkill R. in Gardiner, NY; the hydrograph shows the impact of a then-recent heavy rain on streamflow (an event the students experienced). If desired, instructors can swap this image for a local stream with locally-familiar impacts, or add multiple examples. The USGS website is a good source for streamflow datasets: see resources)

LTER Hydrograph intro material_compressed.pptx (PowerPoint 2007 (.pptx) 18MB Jul28 23) (compressed)

LTER Hydrograph intro material.pptx (PowerPoint 2007 (.pptx) 38MB Jul28 23) (full-size)

  • Instructor: Answer keys for the student worksheet

  • Student handout/ download: Info packets for each site

Information packets on the climate, hydrology, and ecology of each LTER site. Each packet includes an outline/ map of the watershed, a representative picture, the change in elevation from headwater to stream gage, average annual precipitation, precipitation regime, temperature info, etc., so students are able to posit an informed hypothesis regarding what each hydrograph will look like.

Info Packet - Arctic LTER.docx (Microsoft Word 2007 (.docx) 2.5MB Jul28 23)

Info Packet - Hubbard Brook LTER.docx (Microsoft Word 2007 (.docx) 2MB Jul25 23)

Info Packet - Central AZ_Phoenix LTER.docx (Microsoft Word 2007 (.docx) 5.4MB Jul25 23)

Info Packet - McMurdo Dry Valleys LTER.docx (Microsoft Word 2007 (.docx) 2.2MB Jul25 23)

  • Student download:  Commented R scripts for each site, to explore the dataset and plot 1-year hydrographs

Arctic LTER R script (R script 6kB May1 23)

Central AZ - Phoenix LTER R script (R script 6kB May1 23)

Hubbard Brook LTER R script (R script 6kB May1 23)

McMurdo LTER R script (R script 7kB May1 23)

  • Student download: clean streamflow data sets for each site (NOTE: McMurdo has two datasets, one for the full water year and one that focuses on the short flow season for better visualization; this is explained in the McMurdo R script).

ARC_streamflow_2016.csv (Comma Separated Values 438kB Apr17 23)  - Arctic LTER

CAP_streamflow_2016.csv (Comma Separated Values 2.8MB Apr17 23)  - Central AZ - Phoenix LTER

MCM_streamflow_2016_fullyear.csv (Comma Separated Values 387kB Apr17 23)  - McMurdo LTER (full year)

MCM_streamflow_2016.csv (Comma Separated Values 375kB Apr17 23)  - McMurdo LTER (short)

HBR_streamflow_2016.csv (Comma Separated Values 5.2MB Apr17 23)  - Hubbard Brook LTER

  • Student handout/ download: 

module worksheet (Microsoft Word 2007 (.docx) 28kB Jul20 23)

  • Student handout/ download (optional): blank hydrographs for the hypothesis sketch

blank hydrograph (Acrobat (PDF) 179kB Apr17 23)

  • Student and/or Instructor handout (optional): Getting started: installing R and R Studio and creating a working directory in R

Getting started with R and R Studio (Microsoft Word 2007 (.docx) 37kB Jul20 23)

  • Links to explore data that is available at each LTER site

found in the 'References and Resources' section, below

  • Links to other sites to access streamflow data (USGS, NEON, EDI) 

found in the 'References and Resources' section, below

Teaching Notes and Tips

  • R and RStudio installation: use a computer lab with these programs installed, OR make sure students have these programs installed and working *before* class. This will save a lot of headaches! RStudio Cloud is another option that does not require installing the programs locally; see the information link in "References and Resources," below.
  • For the PPT presentation: if you can, use a local hydrograph for the example, especially if it shows a recent or annual water-source event that students are aware of and can readily relate to the change shown in the hydrograph (e.g. a recent heavy rain that increases flow, a spring snowmelt flood pulse, etc.).
  • Site selection: For better discussion and more complete exploration of the LTERs and potential hydrographs: make sure all four of the sites are selected in the class; consider assigning sites or having a signup sheet.
  • When students download their data: make sure they DO NOT open the .csv file outside of R. Some software programs (Apple Numbers, Google Sheets, etc.) modify the timestamp; this causes 'date conversion' errors when students run the R code. If students accidentally open the .csv outside of R and change the timestamp, have them re-download the data file. 
  • Completing the worksheet: This is easiest if the students complete and turn in an electronic version of the worksheet. The worksheet can also be printed out; if you choose to print and hand out hard copies, you may want to adjust spacing and/or have them answer on a separate sheet of paper. 
  • When coding: The red flag-green flag method for coding, described in "Quick Overview/ Activity B" above, is useful for helping instructors assess student progress and identify those who need help. It can also be used to encourage peer interaction and peer support. 
  • When coding: *optional* - if some groups finish much faster than others, they can read about a second site then download, explore, and plot that site's data. 
  • When checking student plots: be aware that the two polar sites, Arctic and McMurdo Dry Valleys, will only have streamflow during the warm months/when the sun is above the horizon and temperatures + solar energy are high enough to allow snow,  ice and permafrost melt.  Remember that the austral summer is ~ December-February
  • The optional sections D and E are stand-alone, e.g. while they both expand on the module topics, they do not depend on one another.  Instructors can choose either or neither optional section for their class; also, either or both can be presented as post-class assignments. 


Overall Learning Goals

  • Learn what a hydrograph is and why they are useful resource management tools
    • Listen to the introductory presentation (Activity A)
    • Demonstrate understanding through discussion and successful worksheet completion
  • Understand how to interpret different hydrographs, including how different water sources can impact the shape of a hydrograph
    • Listen to the introductory presentation (Activity A)
    • Explore and analyze their own site's hydrograph (Activity A - explore and Activity B - analyze)
    • Identify similarities and differences between two different LTER sites (Activity B)
    • Identify additional data or information they would need to support their ideas re: the water sources creating their hydrograph (Activity C)
    • Demonstrate understanding through discussion and successful worksheet completion
  • Learn how to work with large datasets in R, including data exploration, visualization, and analysis
    • Use a provided R script to explore and visualize the data, then plot the site's 1-year hydrograph (Activity A)
    • Use the provided worksheet to analyze what they see in the plotted hydrograph and how it may relate to streamflow sources at their site (Activity B)
    • Demonstrate understanding through discussion, successful hydrograph plotting, and worksheet completion.
    • OPTIONAL: successfully complete activities D and/or E
  • Learn how streamflow is generated in various LTER biomes, including how (and whether!) groundwater plays a role in this
    • Listen to the introductory presentation (Activity A)
    • Read the provided information packets for their site (Activity A)
    • Hypothesize a hydrograph for their site and commenting on potential water sources at key points (a worksheet with blank graphs will be provided) (Activity A)
    • Inter-site hydrograph comparison and discussion (Activity B):
      • Students pair with another group to answer the overarching question re: 'how and why does streamflow vary in different biomes, and how is it the same?'
      • Guided by the worksheet, groups compare their sites and site hydrographs, and discuss reasons for similarities and differences 
    • Original groups compare their hypothesized / sketched hydrograph with the site's actual, data-generated hydrograph. (Activity C)
      • How does the hydrograph data compare with their earlier hypotheses? 
        • Discuss similarities, differences
        • Discuss what might drive the differences between what they hypothesized and what they observed 
        • What hydrologic events may be shaping the actual hydrograph?
      •  What do they know  about water sources/ what causes the hydrograph they see, and what questions do they have AND/OR what needs more support/ information?
    • Demonstrate understanding of the above through small-group discussion and successful worksheet completion
  • The diversity of biomes and hydrology in LTER sites (and by extension around the world)
    • Learn about the hydrology, climate, ecology of at least one of the 4 LTER sites/ biomes: precipitation regime, seasonal temps, sunlight, image of a typical watershed. (Activity A)
    • Participate in an informed discussion re: similarities and differences between their site and other sites in the module. (Activity B)
    • Demonstrate understanding of the above through discussion and successful worksheet completion
    • OPTIONAL: successfully complete activity E, with an informed discussion of how their selected site compares with the module sites (and possibly with other students' selected sites). 

References and Resources

LTER site information: the LTER Network site provides information about the program as a whole as well as individual sites; and individual LTER sites are typically good resources for additional data and information about each site.

NEON data: you can find streamflow and supplemental data here:

Environmental Data Initiative [EDI] data portal

USGS streamflow data

R, RStudio, and RStudio Cloud: