Classroom activity Grade 7 Engineering & Design
Verdant Vale Water Board: A Supply-Options Decision Matrix
Student teams role-play a fictional water board, scoring three competing supply designs on a shared decision matrix and defending one recommendation.
Objectives
- Students will score three competing water-supply designs against shared criteria using a decision matrix.
- Students will recommend one design and justify the choice using their matrix scores.
Vocabulary
Key words: decision matrix, criteria, trade-off, water reuse
Teacher overview
This is a role-play and scoring activity for teams of four. Each team acts as the water board of the fictional town of Verdant Vale, which faces a water shortage and must choose one new supply design. Three options compete: drilling a new groundwater well, building a water reuse system that cleans and reuses wastewater, and launching a strong conservation program. Teams score each option against shared criteria on a decision matrix, add up the scores, and defend a recommendation. A decision matrix is a systematic tool engineers use to compare designs fairly, so scoring every option against the same criteria is the point of the exercise.
Activity Directions
Setup (5 min): Group students into teams of four. Give each team one set of three option cards and one decision-matrix handout. Explain that the fictional town of Verdant Vale must pick one new water supply, and their team is the board that decides.
Assign roles (3 min): Within each team, assign four roles: a budget officer (watches cost), an engineer (watches how well it works and how long it takes), an environmental scientist (watches impact on rivers and the aquifer), and a resident (watches reliability and fairness). Each role reads the option cards with their concern in mind.
Read the options (7 min): Teams read all three option cards: New Well, Water Reuse, and Conservation Program. Each card lists rough cost, how much water the option gains, environmental impact, time to build, and reliability during drought.
Score the matrix (15 min): Teams score each option from 1 (poor) to 5 (excellent) on all five criteria, filling in the decision matrix. Every team member argues from their role before the team agrees on each score. Teams then add each option's five scores for a total.
Recommend (7 min): Each team circles the option with the strongest case and writes two sentences saying why, pointing to specific matrix scores. A high total is not the only reason a team may choose an option; a team may weight one criterion more heavily if it explains the choice.
Debrief (8 min): Ask two or three teams to share their recommendation and one score they argued about the most. Then ask the whole class: "Two teams used the same matrix and the same cards but chose different options. How did that happen?" Guide students to see that teams weighted the criteria differently, which is a normal part of real engineering decisions.
The activity ends when every team has a completed matrix and a written recommendation, and at least two teams have shared during the debrief.
Student Handout
Your team is the water board of the fictional town of Verdant Vale. All figures on the cards below are made up for this activity. Score each option from 1 (poor) to 5 (excellent) on the five criteria, then add each option's scores.
Option A: New Well. Drills into the aquifer. Cost: medium. Water gained: about 2 million gallons per year. Environmental impact: draws down the aquifer, which is already stressed. Time to build: about one year. Reliability in drought: drops if the aquifer keeps falling.
Option B: Water Reuse. Cleans wastewater to reuse it. Cost: high. Water gained: about 3 million gallons per year. Environmental impact: low, since it reuses water the town already has. Time to build: about two years. Reliability in drought: strong, because it does not depend on rain.
Option C: Conservation Program. Pays for low-flow fixtures and leak repairs. Cost: low. Water saved: about 1 million gallons per year. Environmental impact: very low. Time to build: a few months. Reliability in drought: steady, but limited in how much it can save.
Decision matrix (score each cell 1 to 5):
| Criteria | Option A | Option B | Option C |
|---|---|---|---|
| Cost (5 = cheap) | |||
| Water gained | |||
| Environmental impact (5 = low impact) | |||
| Time to build (5 = fast) | |||
| Reliability in drought | |||
| Total |
Which option earned your team's highest total? Write two sentences that point to specific scores.
Which criterion caused the most disagreement on your team, and how did you settle it?
Name one trade-off your recommended option requires the town to accept.
From Water for Schools (waterforschools.org). This material is in the public domain (CC0) and may be copied, edited, and shared freely.
Answer Key
Answer: Accept any option a team can defend with its own matrix scores. There is no single correct choice; a strong answer names specific criteria (for example, "Option B scored highest on reliability and impact") rather than a vague preference.
Answer: Accept any criterion, with an explanation of how the team reached agreement. Common answers involve cost versus reliability, since the cheapest option (Conservation) saves the least water while the most reliable option (Reuse) costs the most.
Answer: Accept a real trade-off tied to the chosen option: a new well strains the aquifer, water reuse costs more and takes longer to build, and conservation alone may not save enough during a severe drought. The trade-off must match the option the team recommended.
Differentiation
Support
Give these teams a matrix with two rows already scored and explained as models, so they focus on the remaining criteria. Provide a simple 1-to-5 scale with words ("1 = poor, 3 = okay, 5 = excellent") printed beside the matrix.
Extension
Have teams add a sixth criterion of their own choosing, decide how to weight it, and rescore the options. Ask them to explain whether the new criterion changed their recommendation and why.
ELL supports
Provide the option cards with a small icon for each criterion (a coin for cost, a droplet for water, a leaf for impact, a clock for time, a shield for reliability). Allow students to argue their role's view with short phrases and to record scores as numbers rather than sentences.