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  Unit IV: Module 16
Geographic Information Systems Laboratory
Basic Spatial Analyses for Lake and Stream Systems


Many impairments to water quality are related to the surrounding landscape. Some of these effects are related to immediate factors such as shoreline characteristics, erosion, and riparian vegetation, while others are related to watershed scale factors, such as land use patterns, the amount of impervious surface, homeowner activities, and numerous other factors.

Geographic Information Systems provide a means to quantify various aspects of lake, riparian, and watershed characteristics. By linking these spatial characteristics with water quality, a water quality manager can identify key sources of impairment, and consequently find appropriate remediation strategies. In addition, the maps created through GIS analyses provide an effective means of conveying information to decision makers and the public.

In this laboratory, you will use on-line GIS resources from WOW and other sites to answer questions on lake, river and watershed attributes for several systems.


  • Explore the GIS tools and resources on WOW, DuluthStreams and Lake Access to find and retrieve spatial data on lakes, rivers and watersheds
  • For any given site, learn to identify a watershed and identify the dominant stressors, particularily land use, that affect water quality.

Part I: Using GIS Tools and Resources on WOW to Compare Urban and Rural Lakes

Use the WOW Internet Map Server (IMS) to retrieve lake and watershed data for Medicine Lake in the western Minneapolis region and Shagawa Lake near Ely, Minnesota, about 250 miles northeast of Medicine Lake. Before you start using IMS, you should look at the Quick Start Primer.

Click one of the following links to launch an IMS session in a separate window:


Use the Identify and Measure tools in IMS to answer the following questions:

The fetch of a lake determines in part its susceptibility to mixing by wind events. What is the longest fetch of Medicine Lake? Shagawa? (note: the prevailing winds in Minnesota are generally from west to east)

Given regional wind patterns, do you think the fetch has a significant effect?

Use IMS to answer following questions, put your answers in the table below:

What is the area of each lake?

What is the maximum depth of Medicine Lake?
(Hint: make Bathymetry the active layer, then use the Identify Tool Identify tool on the deep hole)

What is the maximum depth of Shagawa Lake?
(Hint: go to our cheat sheet)

Use the Query function Query button to determine the amount of forest, agricultural and urban lands in the watershed. Express your answer as a percent of the watershed

Land Use Calculations

  1. Use the IMS Query function to extract the Land Use data from the watershed. You can select data individualy by land use type, or select it at once. The quick way to select it all is to use Area > 0 as your Query String
  2. Save the data and get it into EXCEL - Option 1

    Copying the selected data from the Arc View IMS frame:
    2.1 Select and highlight all all of the fields displayed in the bottom ArcView IMS frame.
    2.2 Right click the mouse key to copy the highlighted fields. Select Copy.
    2.3 Load Excel, click on File> Open a blank worksheet.
    2.4 Highlight the first cell, and right click the mouse to Paste the selected data.
  3. Save the data and get it into EXCEL - Option 2

    Saving the data to a text file:
    3.1 Click on "Save Attributes to Text File" - a help box pops up
    3.2 Choose File>Save As
    3.3 In the Save dialog box, Change the type of file (Save as Type) to text file (txt)
    3.4 Type in a sensible file name and choose a location to save the file. Save it.
    3.5 Load Excel, click on File> Open and select your text file
    3.6 Excel will complain that it doesn't recognize the file.
           Too bad for it, click OK to launch the Text Import Wizard
    3.7 This is a comma delimited file, so make sure the Delimited file type is checked and click on Next
    3.8  Click in the Comma box to tell Excel this is a comma-delimited file. The fields will magically align
    3.9  Click on Finish to load the data into your worksheet.
  4. Calculate the percentages of each land use type in the watershed

    4.1  You will notice that the column headings do not carry over. They are (in order):
                 Area (in square meters - the native format for storing area data)
                 Detailed Description of LandUse type
                 Area(in hectares)
                 Landuse(the more aggregated class used to select the data)
                 Shape- the type of data (in this case - polygon)
                 ID- an index number for the individual polygons
    4.2  There are a number of ways to calculate the percentages
                 Sort the data and use @sum to calculate the subtotals by landuse category
                 A more elegant way is to uUse the Data>Pivot Table function - this is worth exploring
Medicine Lake
Shagawa Lake
Watershed Area (Aw)    
Lake Area (AL)    
AW : AL ratio    
Land Use
Agriculture (%)    
Forest (%)    
Urban (%)    
Other (%)    

How might the differences in water quality between the lakes be related to differences in land use?



How do you think lake water quality might be related to the Aw:AL ratio?



Use the IMS to look at the lake shorelines. How do you think lake water quality differences be related to shoreline development?



What would you suggest is the major environmental stress factor to Medicine Lake? Shagawa Lake?




Part II: Using GIS Tools and Resources on WOW to Assess Stream and River Systems (optional exercise)

Kingsbury Creek (Duluth, MN) originates in a swamp drainage in a level to rolling landscape with light agricultural and exurban (between suburbia and ruralia) land use. It flows along the Duluth-Missabe and Iron Range (DMIR) railyard in the City of Proctor, just outside Duluth, MN. At the DMIR, taconite pellets from the Iron Range are transferred to a second set of rail cars to make the short trip to the ore docks in the Duluth Harbor. The Creek makes a steep drop to Lake Superior, and flows through the Lake Superior Zoo, where the DuluthStreams Stream Monitoring Unit (SMU )is located. From there it is <1 km to its discharge into the St. Louis Estuary/Duluth Harbor in the western arm of Lake Superior.

The Kingsbury Creek IMS Session contains a number of key spatial data layers, including roads, hydrography, land use, and a recently developed impervious surface layer. In addition, a set of high resolution air photos becomes visible when you "zoom in" for a detailed view of the landscape.

Use the IMS tool to follow Kingsbury Creek from its origin in Mogie Lake, through Proctor, and down to the Zoo. By turning different layers on and off, you can get a good idea of what the dominant impairments to this urban stream might be. List the dominant features you have observed.

Select "Real-time Data" as the Active Layer. Using the Hyperlink Tool , click on the Stream Monitoring Site at the Lake Superior Zoo. This will launch the Data Visualization Tool in a separate window. Scroll through the Summer 2003 data and locate a storm event.

How do the various water quality parameters change in response to a rainfall?



What aspects of land use might be responsible for these changes?



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date last updated: Monday May 10 2004