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Modeling A River Environment
For the Teacher

Models are used to represent the "real world," be it a diorama, wooden/plastic model, or a mathematical one. They help the model-builder to understand a particular system and in return provide insight to the lay person in policy adjustments and/or variable adjustments. Models assist us in understanding something new about a system.

As part of the Outdoor Classroom experience students take different measurements of the Honey Creek environment. These measurements include temperature and dissolved oxygen (DO). The amount of dissolved oxygen within a water system is dependent upon many different factors, including: flow rate, temperature, flora, fauna, and chemicals.

The four models presented on this web-site were developed as part of a grant obtained by The University of West Florida's Bioremediation Laboratory to assess agricultural runoff in the Escambia River system and to assist Escambia and Santa Rosa County teachers in teaching about factors that can impinge upon the DO of the river system. The models are very generic (can provide a representative view of any river/creek system) but increases in complexity from 1 to 4. The four mathematical models use STELLA software from High Performance Systems. They are:

1. 1_DO_Temp.stm (illustrates that temperature affects the amount of DO in a water system)
2. 2_DO_h20_flow_temp.stm (uses model 1 plus adds different river flow rates to determine the amount of DO in a river system)
3. 3_DO_Fish_H2O_Temp.stm (uses model 2 plus the addition of fish to the river system to determine the amount of DO)
4. 4_DO_Fish_H20_Temp_food.stm (uses model 3 plus the addition of fish food (algae) to the river system to determine the amount of DO)

The graphical interface for model Number Four (4) is shown on the right. The "reddish" sliders are used to change the river flow, river temperature, and the amount of available food. The "Information" buttons provide the user with the assumptions that went into developing the model. The "To Model Level" takes the user to the model structure. The "Run" button does exactly what it reads-it "runs" the model, providing its output via the yellow graph. The purple indicators show the numbers as the model proceeds through its calculations. The ending numbers represent those variables in year 100. The Restore All Devices/Graphs-Tables buttons restore the model to its "original" beginnings. The table icon provides a pop-up window showing all the variable numbers for each year (1-100).

Click on the "Information 1 & 2" and "To Model Level" icons in the above image to open a new window providing more information. Click on the "Yellow Graph" to open a new window showing six (6) different model runs. The only variable that changed was the amount of available food.

To play with the various models you will need to download the zipped file (hc_stella_models.sit) and using "Stuff-it Expander" available as a free download at http://www.aladdinsys.com to "Unzip" the folder into four separate programs. A copy of STELLA 8 Demo (free download) available at High Performance Systems required to run these four programs. There are links on the High Performance Web-site pointing teachers and students to resources explaining the System's approach to learning.

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