# Spreadsheet analysis of chemical hydrographs

#### Summary

This is a good activity to have students practice spreadsheet analysis skills on a medium large data set. It also helps them understand stream hydrographs and baseflow/quickflow components.

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## Context

#### Audience

I use it in an upper level undergraduate general hydrogeology course.

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

This activity requires basic algebra skills and some familiarity with spreadsheets. The course I use it in has prerequisites of a semester each of calculus, chemistry, and physics.

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

This is an exercise at the end of chapter 1 in the text "Groundwater Science" (2002). The chapter deals with hydrology and surface/subsurface water fluxes.

## Goals

#### Content/concepts goals for this activity

Understanding stream/groundwater interaction, stream hydrographs, baseflow and quickflow components of stream flow, and the concept of chemical hydrograph separation.

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

Using algebra to derive the needed equation from other given equations.
Analyzing a large data set using equations in the spreadsheet.

#### Other skills goals for this activity

Learning how to document a mathematical derivation of an equation and to document units and their consistency in the equations. Learning how to produce a correctly annotated graph with the spreadsheet software.

## Description of the activity/assignment

Students download a comma-delimited data set that is a time series of stream discharge measurements and the concentration of a trace element in the stream. Given the concentration of this element in the precipitation and in the groundwater, the students analyze the data using spreadsheet software to separate the hydrograph into baseflow and quickflow components. Students produce a graph of their results. To do the analysis, students must derive an appropriate equation based on other equations presented in the text (Eqs. 1.2 and 1.3).

## Determining whether students have met the goals

They are asked to derive and annotate the correct equation to use in the spreadsheet, and then must submit a graph showing their resulting hydrograph separation.