Project Grade 12 Science
Aquifer Storage and Recovery for the Lattimore Basin
A grade 12 science capstone in which students test whether winter surplus water can be stored underground, then defend a recommendation to a fictional agency board.
Objectives
- Students will build a seasonal water budget that compares injection capacity with the surplus available.
- Students will evaluate recovery efficiency and water quality risk against stated project constraints.
- Students will defend a recommendation in writing and orally to a stated non-classroom audience.
Vocabulary
- 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: aquifer storage and recovery, injection well, recovery efficiency, native groundwater, feasibility study
Teacher overview
The fictional Lattimore Basin receives more water in February than it can use, while its August demand runs well ahead of supply. Aquifer storage and recovery addresses that mismatch by injecting treated surplus water into an aquifer during the wet season and pumping it back out in the dry season. Over six sessions, student teams test whether the approach is workable for this basin and deliver a feasibility memo and a ten-minute presentation to a fictional groundwater sustainability agency board.
The driving question is whether the basin can store enough winter water underground, at an acceptable cost and an acceptable water quality risk, to cover its summer deficit. A team that computes only injection capacity will find the project easy to approve, while the constraints on recovery efficiency and on arsenic mobilization are what make the recommendation a genuine judgment.
Project Brief
Driving question. Can the fictional Lattimore Water District store winter surplus water underground and recover enough of it in summer to close its dry-season deficit, within the budget and the water quality conditions the agency has set?
Client and audience. Your team is a consulting group reporting to the board of the fictional Lattimore Groundwater Sustainability Agency. The board is not made up of engineers, so the memo and presentation must be understandable to a general audience while carrying the numbers that support the recommendation.
Basin conditions and constraints. All figures below describe the fictional basin and are the only data you may treat as given.
- Winter surplus available for injection, December through March: 1,800 acre-feet
- Summer supply deficit that must be covered: 1,200 acre-feet
- Maximum injection season: 120 days
- Injection wells available: no more than 4, each rated at 900 gpm
- Assumed recovery efficiency for this aquifer: 75 percent of what is injected can be pumped back with acceptable quality
- Capital budget cap: $2.4 million for wells, piping, and instrumentation
- The aquifer's sediments contain naturally occurring arsenic that can dissolve when oxygen-rich injected water enters an oxygen-poor aquifer, so the board requires a monitoring plan
- Conversions you will need: 1 acre-foot = 325,851 gallons; 1 MGD = 694 gpm; there are 1,440 minutes in a day
Required deliverables. Each team turns in two products.
- A feasibility memo of no more than six pages, containing the seasonal water budget, the injection capacity calculation, the recoverable volume, a cost figure expressed per acre-foot of recovered water, a monitoring plan, and a one-paragraph recommendation.
- A ten-minute presentation to the board, with a question period, including at least one chart the team built from its own calculations.
What a strong recommendation does. It states a position, shows the numbers that support it, names the largest uncertainty in the analysis, and describes what the district would monitor to find out whether the assumption held.
Milestones
Session 1, basin briefing and constraints. Read the basin data sheet, restate the driving question in your own words, and produce a one-page constraints table listing every stated limit and what it rules out. Output: the constraints table, checked by the teacher before session 2.
Session 2, injection capacity and water budget. Calculate the daily injection capacity of the well field in gallons per day and in million gallons per day, then the total volume injectable in the 120-day season in acre-feet. Compare that figure with the 1,800 acre-feet of surplus and identify which of the two limits the project. Output: a worked water budget with units shown at every step.
Session 3, recoverable volume and the deficit test. Apply the 75 percent recovery efficiency to your injectable volume, compare the result with the 1,200 acre-foot summer deficit, and calculate the recovery efficiency at which the project would exactly break even against that deficit. Output: a short written finding with both numbers and one sentence on what the break-even value means for risk.
Session 4, water quality and monitoring plan. Research how oxygen-rich injected water can mobilize arsenic from aquifer sediments, then design a monitoring plan naming what will be sampled, where, how often, and what result would trigger a pause in injection. Output: a one-page monitoring plan with a sampling table.
Session 5, cost and trade-offs. Divide the capital budget cap by your recoverable volume to express cost per acre-foot of recovered water, then compare the project against one alternative your team names, such as buying water from a neighboring district or funding a conservation program. Output: a trade-off table scoring both options against cost, reliability, and environmental risk.
Session 6, memo and board presentation. Finish the memo, rehearse once against a timer, and present to the board panel. Output: the submitted memo and the delivered presentation with responses to at least two questions from the panel.
From Water for Schools (waterforschools.org). This material is in the public domain (CC0) and may be copied, edited, and shared freely.
Rubric
Score each criterion from 4 down to 1. A team's total is out of 16 points.
Water budget and capacity analysis
- 4: The water budget carries units correctly from gpm through MGD to acre-feet, identifies whether injection capacity or available surplus is the binding limit, and states the assumption behind every conversion.
- 3: The budget reaches a correct total with units shown, and names the binding limit, but leaves one conversion or assumption unstated.
- 2: The arithmetic is mostly correct yet the units are inconsistent, or the binding limit is asserted without support.
- 1: The budget is incomplete, or capacity is reported without converting to a seasonal volume.
Water quality and monitoring plan
- 4: The plan explains the chemical reason injected water can mobilize arsenic, names sampling locations, frequency, and a specific trigger value or condition that would pause injection.
- 3: The plan names locations and frequency and gives a general trigger, with a partial explanation of the chemistry.
- 2: The plan lists sampling activities without connecting them to the arsenic risk or to any decision the district would make.
- 1: Monitoring is mentioned but not designed.
Cost and trade-off evaluation against constraints
- 4: Cost per acre-foot of recovered water is calculated correctly, the alternative is described fairly, and the comparison weighs cost, reliability, and environmental risk against the stated constraints.
- 3: The cost figure is correct and an alternative is compared, but on fewer than three dimensions or without reference to the constraints.
- 2: A cost figure is given without connecting it to recovered volume, or the alternative is dismissed rather than evaluated.
- 1: Cost is restated from the brief with no analysis.
Memo and board presentation
- 4: The memo is within length, states a clear recommendation, names the largest uncertainty, and the presentation is understandable to non-engineers, keeps to time, and answers panel questions with evidence.
- 3: The recommendation is clear and supported, and the presentation keeps to time, but the uncertainty is named only in passing or one answer lacks evidence.
- 2: The recommendation is present but weakly supported, or the presentation runs over time or relies on technical language the audience would not follow.
- 1: No clear recommendation, or the deliverable is substantially incomplete.
Differentiation
Support
Give these teams a partially completed water budget for the fictional Lattimore Basin with the per-well daily volume already calculated, so the team's work begins at the four-well total and the seasonal conversion. Provide a monitoring plan template with the four column headings filled in, and allow the memo to be four pages rather than six. Check the session 2 output before the team proceeds, since an error there propagates through every later milestone.
Extension
Ask these teams to model recovery efficiency as a variable rather than a fixed value, building a small table or graph of recoverable volume against efficiencies from 55 to 95 percent, and to identify the efficiency below which the fictional project fails the deficit test. Have them add a second constraint of their own choosing, such as a limit on how far the injected water may travel from the well, and explain how it changes the recommendation.
ELL supports
Provide a bilingual glossary card for the six vocabulary terms, each with a simple cross-section sketch showing injection and recovery. Give the memo a section-by-section outline with one guiding question per section, and allow the board presentation to be delivered from a written script. Assign roles within teams so that a student still building spoken fluency can take the chart-building and data-checking role in early sessions and a speaking role in the final one.
Extensions
Teams can compare the fictional Lattimore proposal against a surface reservoir sized to hold the same 1,200 acre-feet, listing the evaporation, land, and permitting differences between storing water above ground and below it. A second option is to research whether the state where the school sits regulates underground injection for storage, and to summarize in one page what a district there would have to demonstrate before receiving a permit.