# Quantifying Groundwater Baseflow and Improving Math Skills through a Stream-Discharge Exercise

James Reichard
,
Georgia Southern University
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#### Summary

A two-part exercise is presented where students quantify stream discharge and use the data to determine groundwater baseflow. They first use tedious hand calculations to compute discharge; then develop their own spreadsheets to perform the calculations more efficiently and accurately. Finally, students collect field data and use their spreadsheets to determine discharge and to calculate some simple statistics.

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## Context

#### Audience

This exercise is designed for undergraduate students taking a course in hydrogeology. Course requires students to have taken college algebra, but not calculus. They also are required to have taken physical geology; mineralogy and sedimentary petrology and stratigraphy are recommended, but not required.

#### Skills and concepts that students must have mastered

Students are able to do basic college algebra and be proficient in unit conversions. They also should have a basic working knowledge of Excel spreadsheets.

#### How the activity is situated in the course

This activity is designed as part of a series of lab/field exercises and problem sets in a hydrogeology course. However, this activity can also be used as a stand-alone exercise.

## Goals

#### Content/concepts goals for this activity

1. Better understand the relationship between groundwater baseflow and stream discharge.
2. Strengthen and develop mathematical skills by computing stream discharge using hand calculations and spreadsheet analysis.
3. Make both #1 and #2 more meaningful by having students collect their own field data.
4. Be able to determine groundwater baseflow and tributary inputs along a river.
5. Learn to perform error analysis on replicate measurements.

#### Higher order thinking skills goals for this activity

This exercise requires student to critically analyze and interpret data; includes basic statistics and error analysis.

## Description of the activity/assignment

In week one of the exercise students determine stream discharge by doing some tedious, but simple hand calculations using data sets provided by the instructor. The following week is designed to be more hands-on. Here, they collect their own field data and create a spreadsheet to perform the calculations more efficiently and accurately. By collecting the data themselves, students gain a more thorough understanding of how stream discharge is both measured and computed; they also learn how the results can be used to determine groundwater baseflow. The fact they do hand calculations prior to creating the spreadsheet helps build their math skills and reduces the "black-box" effect that often develops when using software for data analysis. Students also gain valuable experience creating spreadsheets and learn how this tool can be used to perform repetitive computations more efficiently and with less error. Finally, this exercise asks students to consider the accuracy of their replicate field measurements through a series of questions related to their standard deviation and percent error calculations.

## Determining whether students have met the goals

Learning outcomes are assessed based on the following:
1. Accuracy and quality of the lab reports that correspond to these exercises.
2. Ability of individual students to answer questions on lecture exam related to:
• a) Performing stream discharge measurements and computations.
• b) Determining groundwater baseflow from a series of stream discharge data points.
3. Ease with which students can create more complex spreadsheets in subsequent lab exercises.
4. Ability of students to apply error analysis to future lab exercises involving replicate measurements and to interpret the meaning of the analysis. 