Classroom activity Grade 8 Science
Mapping a Contaminant Plume in the Meadowbrook Aquifer
A grade 8 science activity where groups build a sand aquifer model, release a dye contaminant, and map how the plume spreads toward a well.
Objectives
- Students will model how a contaminant spreads through an aquifer toward a pumping well.
- Students will map a contaminant plume and describe its direction and spread over time.
- Students will explain how a monitoring well helps detect and reduce groundwater pollution.
Vocabulary
- Aquifer
- An aquifer is an underground layer of rock, sand, or gravel that holds water in the tiny spaces between its grains. Wells reach down into aquifers to bring water up to the surface.
- Monitoring well
- A monitoring well is a well drilled specifically to check on groundwater, not to supply drinking water. Scientists use monitoring wells to measure how high the water table is and to test for pollution before it can spread.
- Contaminant
- A contaminant is anything in water that should not be there, whether it is a germ, a chemical, or too much of a natural mineral, that could make the water unsafe or unpleasant to use. Treatment plants are built specifically to find and remove contaminants before water reaches the tap.
Also: plume, groundwater flow
Teacher overview
Groundwater does not sit still; it moves slowly through the spaces between grains of sand and gravel, and it can carry pollution with it. This activity, set in the fictional Meadowbrook wellfield, has groups of 4 build a small aquifer in a clear tub, release a few drops of dye as a pretend contaminant, and watch it form a plume that drifts toward a pumping well. The model maps directly onto the real system: the sand is the aquifer, the dye is dissolved contamination, and the perforated cup is a drinking-water well. Students map the plume over time to see why utilities place monitoring wells between a possible pollution source and the wells that supply homes.
Activity Directions
Build the aquifer model (10 min). Give each group of 4 a clear tub. Have them add a 1-inch layer of fine gravel, then a 3-inch layer of clean sand on top, sloping the sand gently so one end is slightly higher. The higher end is "uphill," where groundwater will flow from; the lower end is where the well sits.
Add the water table (5 min). Groups slowly pour water into the low end until the sand is saturated and a shallow pool of water sits at the surface near the low end. This water surface is the water table. Press the perforated cup or slotted straw down into the sand near the low end to act as the drinking-water well.
Release the contaminant (5 min). At the high end, students place three drops of dark food coloring on the sand surface at a single spot, the pretend spill site. They record the starting location of the spill on their grid sheet and do not stir the sand.
Simulate rain and pumping (10 min). One student lightly sprays water over the high end to act as rain soaking in, while another gently scoops small amounts of water out of the well cup to act as pumping. Groups watch the colored plume stretch from the spill site toward the well. Remind students this is a model only, and no water in the activity should be tasted.
Map the plume (10 min). Every 2 minutes, students trace the outline of the colored plume onto their grid sheet and label the time. After three tracings, they should have a record of how far and in which direction the plume moved.
Debrief (5 min). Gather groups and work through the debrief questions together, connecting each observation back to real groundwater and monitoring wells. End the activity once every group has answered the debrief questions.
From Water for Schools (waterforschools.org). This material is in the public domain (CC0) and may be copied, edited, and shared freely.
Answer Key
- Debrief question: "In which direction did the colored plume move across your model, and what pulled it that way?" Answer: The plume moved from the high end toward the well.
Groundwater flowed downhill through the sand toward the low end, and the pumping at the well pulled water and the dissolved dye toward it, so the plume stretched from the spill site to the well. - Debrief question: "How did the dye reach the well even though the spill started some distance away?" Answer: The contaminant traveled through connected pore spaces.
Even though the spill started some distance away, groundwater moves through the connected gaps between sand grains, carrying dissolved contamination along with it until it reaches the well. - Debrief question: "Where could a utility place a monitoring well to get early warning of a contaminant, and why there?" Answer: A monitoring well between the spill and the supply well gives early warning.
A monitoring well placed between a possible pollution source and the drinking-water well would show color first, letting the utility detect the problem and act before the contamination reached the water people drink. - Debrief question: "If a real contaminant reached the Meadowbrook aquifer, what could the town do to reduce the harm?" Answer: Stop the source or treat the water.
Meadowbrook could reduce the impact by stopping the spill at its source, pumping and treating the contaminated water, or temporarily switching the town to another water source while the aquifer is cleaned. - Debrief question: "Why is cleaning up polluted groundwater harder than cleaning a spill you can see on the surface?" Answer: Groundwater cleanup is slow and hidden.
Groundwater moves slowly and out of sight through the whole thickness of an aquifer, so a plume spreads through the pores and can take years to clean, which is much harder than cleaning a visible surface spill.
Differentiation
Support (below grade level)
Run one model as a whole-class demonstration first, narrating each step, before groups build their own. Give students a pre-drawn grid with the spill site and the well already marked so they only trace the plume.
Extension (above grade level)
Have students add a second well as a monitoring well between the spill and the drinking-water well, predict which well will show color first, and test their prediction, then explain how spacing between wells affects warning time.
ELL supports
Pair the spoken terms "aquifer," "plume," and "well" with the physical parts of the model as you name them, and provide picture labels to place on the tub. Allow students to answer debrief questions by pointing to their maps and using short phrases.
Extensions
Have students research whether their community's drinking water comes from groundwater or surface water, and if it is groundwater, discuss what kinds of surface activities near a wellfield a town might limit to protect the aquifer from a plume like the one they modeled.