Pop Bottle Hydrograph
Summary
Create hydrograph and explore changes in physical parameters on form of hydrograph. Set up is easy: water is sprinkled into a model watershed (sand in pop bottle) and allowed to dribble onto cheap digital scale. Students record weight of water over time, convert to volume, and plot data.
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Context
Audience
Large (50-100 students) lecture section of environmental geology course for non-majors (largely non-science majors). Class has separate 2 hr/week lab.
Skills and concepts that students must have mastered
In previous lecture(s), students have seen and discussed terms/graph/figures/concepts: river stage, velocity, cross-sectional area, discharge, hydrograph and its components, changes in hydrographs based on storm type, location along stream, region, etc. In short, they have had the usual intro to rivers and floods.
How the activity is situated in the course
In-class activity during last half of lecture period. Students also have weekly 2-hour lab, so assessment/grading is minimized in the exercise, but activity could be developed into lab (some ideas included).
Experiments take ~10 min to run and ~ 5 to discuss. Need 1-3 student volunteers.
Experiments take ~10 min to run and ~ 5 to discuss. Need 1-3 student volunteers.
Goals
Content/concepts goals for this activity
Form of hydrograph: lag time, peak discharge, rising and falling limb, etc.
Reinforce basic skills: data collection, setting up a table, unit conversion, plotting data.
Terms: unsaturated zone characteristics, effect of impermeable surfaces and sewering, effect of vegetation, etc.
Reinforce basic skills: data collection, setting up a table, unit conversion, plotting data.
Terms: unsaturated zone characteristics, effect of impermeable surfaces and sewering, effect of vegetation, etc.
Higher order thinking skills goals for this activity
Analysis of data: examination of data they collect and plot
Transformation of data: measure weight over time but plot discharge. Analogous to stage-time graph conversion to hydrograph (but does not address rating curves).
Formulation of hypothesis: following basic model, have students discuss expectations for altered models before these are run.
Transformation of data: measure weight over time but plot discharge. Analogous to stage-time graph conversion to hydrograph (but does not address rating curves).
Formulation of hypothesis: following basic model, have students discuss expectations for altered models before these are run.
Other skills goals for this activity
Brainstorm to design ther experiments that can address advanced ideas:
-Calculate a water balance to determine amount of transport vs. storage in the watershed if components are weighed before and after.
-Insert gutters (straws) that will make system more "flashy"
-Add sponge or vegetation to increase peak lag time and decrease rising limb (Admission: I haven't tried this!)
-Compare different materials (gravel vs. silt) and examine transmissivity (note, to save time, can be completed side-by-side tests to just compare time.)
-Just re-run first setup to examine effect of antecedent moisture (see caveat in challenges!)
-Calculate a water balance to determine amount of transport vs. storage in the watershed if components are weighed before and after.
-Insert gutters (straws) that will make system more "flashy"
-Add sponge or vegetation to increase peak lag time and decrease rising limb (Admission: I haven't tried this!)
-Compare different materials (gravel vs. silt) and examine transmissivity (note, to save time, can be completed side-by-side tests to just compare time.)
-Just re-run first setup to examine effect of antecedent moisture (see caveat in challenges!)
Description of the activity/assignment
Create hydrograph and explore changes in physical parameters on form of hydrograph. Set up is easy: water is sprinkled into a model watershed (sand in pop bottle) and allowed to dribble onto cheap digital scale. Students record weight of water over time, convert to volume, and then create hydrograph. More complicated pop-bottle watersheds can model effect of urbanization, antecedent moisture, changes in precipitation, changes in "soil" porosity/permeability, etc. SEE TEACHING MATERIALS AND TIPS FOR DETAILS!
Determining whether students have met the goals
Ideas for determining what students have learned:
- Have students draw concept sketch (of sorts) that includes 2 hydrographs for different settings (urban vs. forest, upstream vs. downstream floods) with labels (lag time, rising limb, falling limb, peak discharge) and short descriptions that explain why the hydrographs are shaped as they drew them. Would be quick to grade but synthesizes lots of info.
- Would be good to develop questions that test misconceptions.
More information about assessment tools and techniques.- Have students draw concept sketch (of sorts) that includes 2 hydrographs for different settings (urban vs. forest, upstream vs. downstream floods) with labels (lag time, rising limb, falling limb, peak discharge) and short descriptions that explain why the hydrographs are shaped as they drew them. Would be quick to grade but synthesizes lots of info.
- Would be good to develop questions that test misconceptions.
Teaching materials and tips
- Activity Description/Assignment (Microsoft Word 97kB Jul16 08)
Other Materials
- Form for data collection and graph (Excel 31kB Apr30 08)
Supporting references/URLs
I adapted this from similar in-class rainfall event used by Josh Roering at the University of Oregon. His set up and handouts can be accessed at: http://www.uoregon.edu/%7Ejroering/hydrologicresponse.html