Teach the Earth > > > Hydrologic Cycle and Water Balance Equation

Hydrologic Cycle and Water Balance Equation

Eric W. Peterson
Illinois State University
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This activity was selected for the On the Cutting Edge Reviewed Teaching Collection

This activity has received positive reviews in a peer review process involving five review categories. The five categories included in the process are

  • Scientific Accuracy
  • Alignment of Learning Goals, Activities, and Assessments
  • Pedagogic Effectiveness
  • Robustness (usability and dependability of all components)
  • Completeness of the ActivitySheet web page

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This page first made public: Aug 5, 2005


The assignment works with the mass balance equation in concert with the hydrologic cycle. Students create both a conceptual model and a mathematical model to represent the hydrologic cycle for a basin.

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The assignment is designed for either an undergraduate hydrology or hydrogeology course. Modifications to the assignment could be made in order to be more appropriate for graduate students.

Skills and concepts that students must have mastered

Students should have an understanding of the hydrologic cycle and the mass balance equation. Complete mastery of those concepts is not required. Familiarity with Excel is suggested, but again not required.

How the activity is situated in the course

The exercise is introduced after a discussion of both the hydrologic cycle and the water budget (mass balance) equation.


Content/concepts goals for this activity

Through modeling, both conceptual and mathematical, students will analyze the roles of the various water pathways on the reservoirs within a basin.

Higher order thinking skills goals for this activity

Students will create a conceptual model of the hydrologic cycle for a basin. Using the conceptual model, students will design a mathematical model using Excel. Through variations in the input (or output) parameters, students will evaluate how various changes in the hydrologic cycle affect the basin.

Other skills goals for this activity

Students will gain experience in using Excel.

Description of the activity/assignment

This exercise is designed to evaluate the students' understanding of both the hydrologic cycle and the water budget (mass balance) equation. In my course, the exercise is the students' first exposure to models in the course. While the exercise may seem basic, students gain experience in creating conceptual models and then generating mathematical models from the conceptual model. The exercise provides students with an introduction (or refresher) to some basic Excel formulas. Finally, the exercise can be modified to include more "what if" scenarios that require critical thinking and analysis from the students.

Determining whether students have met the goals

Students submit the conceptual model, the Excel spreadsheet, and answers to the questions for grading.

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