An explorer's map of Western Australia with river systems glowing blue and mineral deposits marked
Year 7 · Unit 01 · Lesson 03

Water: The Resource Behind the Resources

One idea must land: it's not just where the water is — it's when it arrives. Average is a liar.

Their Lesson 2 map has a missing layer, and today they find it. Students become water security advisors — wagering rainfall estimates before the data lands, opening four real WA case files, and discovering why the driest resource region in the state runs on a pipe built in 1903.

Spark

The rainfall wager

Anchor them: Perth gets about 730 mm a year. Then estimates locked, with a confidence rating, for Broome, Marble Bar and Kalgoorlie — before any teaching. The reveal (BoM long-term averages): Broome ≈ 615, Marble Bar ≈ 360, Kalgoorlie ≈ 265.

Tropical Broome is nearly as “wet” as Perth — then the catch: almost all of it lands December–March. Nine dry months on a good average. Say the line and make them finish it all year: average is a… liar.
Core

Location · distribution · variability

Three ideas on one map: where water sits (the tropical north, the east coast, the south-west corner — and the dry heart), who it’s shared between (not where the mines are — hold last lesson’s map beside a rainfall map and let the mismatch do the teaching), and when it arrives (rivers that are dust in September, dangerous in February).

The industry hook gets one line only: every operation on their map drinks. Where a mine actually finds water is tomorrow’s lesson — don’t spend it today.
Workshop

The Water Files

Four evidence cards, face down: the shrinking South West dams, the giant-in-the-wrong-place Lake Argyle, the 1903 Goldfields pipeline, and the Pilbara’s hidden groundwater. For each: predict first in the handout, then open the file, then confirm or revise. Close with the Advisor’s Verdict — rank all four for the next fifty years.

There is no single right ranking — there are only defended rankings. Revising a verdict on evidence gets praised out loud; that’s what professionals do.
Land it

Exit ticket + calibration

Prove “average is a liar” using Broome; one source-and-region from memory; a prediction for next lesson (where does a Pilbara mine get millions of litres a day?); and the calibration check — how many “sure” estimates were actually close? Instinct versus data is an advisor’s first lesson.

Teacher intel

Where does the water in YOUR tap come from, right now? (Most won’t know — the perfect humility hook.)
Is a river that floods once a year reliable? For whom?
Why would you build a 560 km pipe in 1903 — what did the Goldfields have that made it worth it?
What does an average hide?
Watch for“North = dry” (Broome breaks it) · “rain = supply” (no catchment, no storage, no supply) · “the pipeline must be modern” (1903 — older than the ute).
Running shortDrop File 4 (Pilbara groundwater — Lesson 4 covers it properly). Protect the wager, the verdict ranking and the exit ticket.
SupportEvidence cards carry a pre-boxed key fact; pairs read one file each and teach the team.
ExtendFile 5: desalination. Perth drinks the ocean through two plants — is desalinated water “renewable”? Energy is the thread worth pulling.