Salt Tracer and Area-Velocity Water Discharge

Catherine Riihimaki
Drew University
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Problem set on water discharge measurements done during an earlier class meeting. Could also be done as a lab.

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This activity has been done in an introductory, quantitative environmental science course as well as an advanced geomorphology course.

Skills and concepts that students must have mastered

They need to understand the meaning of "area under a curve" and should be comfortable with algebra and dimensional analysis. This activity focuses on conservation of mass, as well.

How the activity is situated in the course

This is a problem set based on field measurements done in an earlier class.


Content/concepts goals for this activity

calculating water discharge using two different techniques

Higher order thinking skills goals for this activity

analyzing field data, error analysis, complex plot interpretation

Other skills goals for this activity

operating field equipment such as velocity meters and electrical conductivity meters
observing stream conditions in situ

Description of the activity/assignment

Students spend a 50-minute class (or longer) measuring water discharge of a local stream. They use two different techniques: the traditional area-velocity method and a salt-tracer method. In the classroom, each student using Excel or Kaleidagraph to calculate discharge from field measurements. They summarize their results in an essay, and assess differences between the two techniques and potential sources of error.
Designed for a geomorphology course
Designed for an introductory geology course
Addresses student fear of quantitative aspect and/or inadequate quantitative skills

Determining whether students have met the goals

The students turn in plots, calculations, and their summary. There is no answer key because all field measurements will be somewhat different.

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