Project Grade 10 Engineering & Design
Merritt Hollow's Water Supply Gap: A Drought Portfolio Project
A grade 10 engineering project where teams size well, reuse, conservation, and desalination options to close a fictional town's water-supply gap on a budget.
Objectives
- Students will convert a water-supply gap among gallons, million gallons per day, and acre-feet per year.
- Students will size a portfolio of supply options that together close a stated supply gap within a budget.
- Students will justify a recommendation using cost, reliability, energy, and environmental trade-offs.
Vocabulary
- Desalination
- Turning salty water, like ocean water, into fresh water people can use. It works, but it takes a lot of energy and leaves behind very salty water that must be handled carefully.
- Acre-foot
- The amount of water it takes to cover one acre of land, about the size of a football field, one foot deep. Western states use acre-feet to measure large amounts of water.
Also: supply gap, water reuse, reliability
Teacher overview
The fictional town of Merritt Hollow expects its water demand to outgrow its current supply within the next fifteen years, and a recent drought showed how thin its margin already is. Over four sessions, teams act as consulting engineers who must close that projected supply gap by combining several options, each with its own yield, cost, energy use, and reliability. The driving question forces real trade-offs, because no single option is cheap, drought-proof, and low-energy all at once. Teams deliver a written recommendation and a short presentation to the fictional Merritt Hollow Water District Board.
Project Brief
Driving question: Which mix of supply options will close Merritt Hollow's water-supply gap most reliably, and still fit the budget?
Scenario: The fictional Merritt Hollow Water District has a problem. It projects that demand will outstrip supply by 1.5 MGD within fifteen years. The board wants engineering teams to recommend new supply options. Each team must defend its plan at a public board meeting.
Given data (a fictional scenario built for this project). Teams receive this on the supply-option data sheet:
- The gap to close is 1.5 MGD.
- The capital budget is 18 million dollars.
- Option A is a new groundwater well field. It yields 0.6 MGD and costs 4 million dollars. It uses low energy. Its risk is drawing the aquifer down faster than it refills.
- Option B is expanded water reuse for irrigation. It yields 0.8 MGD and costs 9 million dollars. It uses moderate energy. It stays reliable during drought.
- Option C is a conservation and leak-repair program. It saves 0.5 MGD and costs 2 million dollars. It uses very low energy. Its savings depend on public participation.
- Option D is a small brackish desalination unit. It yields 0.7 MGD and costs 11 million dollars. It uses high energy, because reverse osmosis needs more power than normal treatment. It also makes a salty concentrate that must be disposed of.
Constraints:
- The mix must close the full 1.5 MGD gap, or explain how close it comes.
- The total cost must stay within the 18-million-dollar budget.
- The plan must weigh reliability, energy use, and the environment, not just cost.
Final deliverable: A written recommendation of two to three pages to the fictional Merritt Hollow Water District Board. It must state the gap in more than one unit. It must include a comparison matrix. It must name the chosen mix, its total yield, and its total cost. A short paragraph must defend the trade-offs. Teams also give a brief presentation.
Milestones
Session 1 (60 min) — Quantify the gap and each option's yield: Teams restate the 1.5 MGD gap in two ways. First they find gallons per day. Then they find acre-feet per year, using 1 acre-foot equals 325,851 gallons and 365 days per year. This lets the board compare the gap to yearly water-rights figures. Teams then list each option's yield from the data sheet. Output: a completed conversion sheet and an option-yield list.
Session 2 (60 min) — Build the comparison matrix: Teams score every option in a matrix. The columns are yield, capital cost, cost per unit of yield, energy use, drought reliability, and environmental impact. Each score is short and clear. Output: a completed matrix with a note on each option's biggest strength and biggest drawback.
Session 3 (60 min) — Choose and check a portfolio: Teams pick a mix of options that closes the 1.5 MGD gap. They confirm the total cost stays within the 18-million-dollar budget. Then they write a short justification of the trade-offs behind their mix. Output: a chosen portfolio with its total yield, total cost, and a written justification.
Final session (60 min) — Write and present the recommendation: Teams finish the written recommendation. It includes the gap in more than one unit, the comparison matrix, the chosen mix, and the trade-off paragraph. Teams then present to the class, which role-plays the water district board. Output: a completed recommendation and a short presentation.
From Water for Schools (waterforschools.org). This material is in the public domain (CC0) and may be copied, edited, and shared freely.
Rubric
| Criterion | Emerging | Developing | Proficient | Advanced |
|---|---|---|---|---|
| Gap-closing yield | The portfolio's combined yield is not calculated or does not address the gap | The combined yield is calculated but falls short of the gap with no explanation | The portfolio's combined yield closes the full supply gap, shown with the numbers added up | The portfolio closes the gap with a small reliability margin, and the team explains why that margin matters during drought |
| Budget and cost-effectiveness | Total capital cost is missing or exceeds the budget with no adjustment | Total cost is near the budget but is not itemized or is slightly over | Total capital cost is at or under the budget with an itemized list | Total cost is within budget, itemized, and the team compares cost per unit of yield across options to defend the mix |
| Trade-off analysis and presentation | The recommendation names options but does not weigh reliability, energy, or environment | The recommendation weighs one factor beyond cost but not the others | The recommendation weighs cost, reliability, energy, and environmental impact together | The recommendation weighs all four factors and anticipates a likely question from the board about a weakness in the plan |
Differentiation
Support (below grade level)
Provide the unit conversions in Milestone 1 already set up with labeled blanks, and give teams a partly filled comparison matrix so they focus on comparing and choosing options rather than building the table format from scratch.
Extension (above grade level)
Ask teams to recommend a second, backup portfolio that would close the gap if the conservation program only reached half of its projected savings, and to explain which other option they would expand to make up the difference and at what added cost.
ELL supports
Provide the supply-option data sheet as a labeled table with simple icons for each option (a well, a recycled-water pipe, a dripping faucet with a wrench, a membrane unit), and provide sentence frames for the trade-off paragraph, such as "We chose ___ and ___ because together they yield enough to close the gap while staying under the budget, and they stay reliable during drought because ___."
Extensions
Invite a planner or engineer from a regional water agency to hear two or three teams present and to describe how a real utility weighs the same options, including how agencies plan for a reliability margin above the minimum gap so a single source failing does not leave the town short.