Survey focus: closing the water loop
Ākonga work out what rainwater and greywater systems can actually supply, and where health or consent constraints bind.
- Applied Survey move: Supply calculation against a real demand
- Evidence it produces: A feasibility judgement with the binding constraint named
Lesson at a Glance | He Tirohanga Whakamua
Ngā Whāinga Ako | Learning Intentions
Students will know
- How rainwater harvesting works as a technology: collection surface, first-flush diverter, storage tank, filtration, and use-appropriate distribution.
- How greywater recycling differs from rainwater harvesting: greywater is used water from baths, showers, and sinks — it must be treated before reuse and cannot be used on food crops without additional treatment.
- That in Māori worldview, wai (water) is not simply a resource — it is a living being with mauri, connected to the health of the people who drink from it and the land it flows through.
- That NZ has significant freshwater quality and allocation challenges, and that these are contested politically, culturally, and economically in ways that water technology alone cannot resolve.
Students will demonstrate
- By comparing three water system approaches across four criteria — including kaitiakitanga obligation — and identifying the appropriate system for at least two different contexts.
- By designing a water system for a specific context (rural home, school, urban apartment block) that addresses the primary constraint of that context.
- By writing Design Journal Entry 17: a 3–4 sentence response on what it means to be a kaitiaki of wai — and what that obligation would require of a water system designer today.
Do Now | Tīmatanga Whakaaro (7 min)
Display on the board — 2 minutes individual, 5 minutes class discussion:
"When you turn on your kitchen tap, where does the water come from? When it goes down the drain, where does it go? How much energy is used in each direction?"
Most students know water comes from "the council" or "a reservoir" but not the specifics. Prompt: "If you live in Auckland, most of your water comes from dams in the Hunua and Waitākere Ranges, topped up by water taken from the Waikato River — treated, pumped through thousands of kilometres of pipes, and pressurised into your home. When you flush the toilet, it travels to a wastewater treatment plant, is partially treated, and is discharged to the sea or river. Both journeys use electricity — treating and pumping water is one of the largest electricity consumers in most NZ cities." Water infrastructure is invisible until it fails. This lesson makes it visible.
Teacher note: Watercare (Auckland's water utility) supplies around 350 million litres of water a day, and operates more than 16,000 km of water and wastewater network (Watercare, 2025). Energy use is approximately 70–80 GWh/year — comparable to running 30,000 average homes. For a city already committed to 85% renewable electricity, water infrastructure is one of the less-noticed large electricity consumers. The energy-water nexus is relevant for students who've studied energy in Lesson 13.
Three Water Systems | Ngā Pūnaha Wai (15 min)
Each water system represents a different relationship between humans and the water cycle — a different degree of dependence on centralised infrastructure and different implications for resilience, equity, and ecological impact.
🏙️ Mains (Reticulated) Supply
Water is sourced from rivers, lakes, or aquifers, treated to drinking standard, and distributed through a network of pressurised pipes to every property. The default system for all NZ urban areas.
LCA: Very high energy use (pumping and treatment), large infrastructure embodied carbon (9,000 km pipes in Auckland alone), significant water loss through pipe leaks (up to 20% in older systems), centralised treatment that handles pathogen risk well.
Advantage: Reliable, consistent, requires no on-site infrastructure from the user. Water treated to the same standard for everyone on the network.
Gap: Removes the user's relationship to water source and quality. When the source is polluted (as with Havelock North 2016), the system transmits the problem at scale.
🌧️ Rainwater Harvesting
Rainfall is collected from roof catchment surfaces, diverted past a first-flush diverter (which discards the first dirty flow), stored in a tank (500L–100,000L), and distributed by gravity or small pump for drinking or non-potable uses.
LCA: Very low energy use (gravity-fed systems use near zero); manufacturing carbon for tank and pipe is recovered quickly; reduces pressure on catchment systems during drought. Requires regular maintenance (tank cleaning, filter checks).
Best contexts: Rural properties (where mains supply doesn't reach), schools for toilet flushing and irrigation, urban homes for garden water during restrictions.
Kaitiakitanga alignment: Keeps the user in relationship with rainfall patterns, seasonal availability, and local water cycles. A full tank after rain is immediately visible; a near-empty tank demands conscious water conservation.
♻️ Greywater Recycling
Water from baths, showers, and bathroom sinks (not toilets, not kitchen sinks with food waste) is collected, treated to an appropriate level, and reused — typically for toilet flushing, garden irrigation, or laundry.
LCA: Reduces fresh water demand by 30–50% in a household. Treatment systems range from simple diversion with time limits (lower treatment, garden only) to biofilter or membrane systems (higher treatment, toilet flushing). Treatment energy varies significantly by system type.
NZ regulation: NZ permitted development rules for greywater reuse vary by council. Generally, simple gravity diversion to sub-surface garden irrigation is permitted; more complex indoor reuse requires resource consent.
Health risk: Greywater contains skin cells, soap, bacteria, and sometimes pathogens. It must never be used on edible-crop surfaces, sprayed in a way that creates aerosols, or stored for more than 24 hours without treatment.
Video: Water Quality Science and Wai in Aotearoa (8 min)
Meet the Water Quality Lab — Waikato Regional Council (5 min 41 sec)
Water quality monitoring uses science to measure what is in the water. What kinds of things are scientists looking for — and who do they report that information to?
What indicators does the lab measure? Who uses the data, and for what decisions? Is there any mention of Māori interests in water quality — and if not, what does that absence tell you?
Water quality measurement can tell you if water is safe to drink. Can it tell you if water is healthy in the kaitiakitanga sense — if its mauri is intact? What would that measurement look like?
Teacher note: The Waikato Regional Council's water quality monitoring is genuine science and genuine public service. The bridge question from the video is: scientific water quality measurement tells us about chemical and biological parameters — E. coli, nitrogen, turbidity. Māori understanding of wai extends to the mauri of the water — its life force and the health of its relationship to the people who depend on it. These are not competing frameworks — they are complementary. The Waikato-Tainui settlement included the Waikato River Authority, which has both scientific and cultural oversight of river health. This is a real example of both frameworks being used together in NZ law.
NZ Water Context | Te Wai o Aotearoa (10 min)
Waikato River and Waikato-Tainui
The Waikato River is the ancestor of Waikato-Tainui. It is also the primary water source for much of the greater Auckland region and is subject to intensive dairy farming and hydro dam impacts. The 1995 Waikato Raupatu Claims Settlement included acknowledgement of Crown responsibility for river health damage. The Waikato River Authority (established 2010) brings together Waikato-Tainui and seven other iwi with the Crown and local government to oversee river restoration. Annual budget: $15M for restoration. This is a genuine kaitiakitanga-in-practice example — but the river remains significantly degraded.
Three Waters Reform and Beyond
NZ's 2021–2023 Three Waters Reform (drinking water, wastewater, stormwater) attempted to consolidate 67 local water providers into larger regional entities for infrastructure investment. The reform was controversial — partly because it proposed to separate water infrastructure from local democratic control, and partly because Māori water rights and interests were not fully resolved. The reform was reversed by the new government in 2023. NZ's water infrastructure challenge remains: ageing pipes, billions in deferred maintenance, boil-water notices in multiple small towns, and the ongoing question of who is the kaitiaki of wai at the system level.
Rural water access: Many rural NZ households and marae rely on roof-collection rainwater as their primary supply — there is no mains alternative. This is simultaneously a heritage practice (traditional collection) and a resilience gap (no backup during dry periods, potential contamination from roof materials or bird droppings). Water technology design for rural Māori communities must respect existing practice while improving health outcomes.
Activity: Water System Design Challenge | He Pūnaha Wai (12 min)
Design a Water System for a Specific Context
Choose one context from the three below. Design a water system that addresses the primary constraint of that context. You may use mains supply, rainwater harvesting, greywater recycling, or a combination. Answer the five questions for your chosen context.
600 km² farm, no mains supply, 1,200 mm annual rainfall, house for 6 people, nearby awa (stream) used for kaimoana collection. Primary risk: summer drought, and roofing material that may contain lead paint.
400 students, Auckland, mains-connected, 1,200 mm annual rainfall, large roof area, toilets are 40% of water use, school garden irrigated by sprinklers on mains. Primary issue: rising water costs and a climate commitment.
8-storey, 80 apartments, Wellington, mains-connected, limited roof area, building undergoing refurbishment, shared laundry, no garden. Primary issue: high per-unit water costs and new earthquake-strengthened building as opportunity to add infrastructure.
Name each component. What is the flow path from source to use to disposal?
What % of the context's water needs does your system supply? What remains on mains?
Name the primary contamination risk and how your system addresses it.
How does your system keep the user in relationship with the local water cycle? What would the kaitiaki of the nearest wai say about it?
Bonus question for Context A: The stream is used for kaimoana. Does any part of your water system discharge to that stream? If yes, what kaitiakitanga obligation does that create?
📓 Design Journal — Entry 17: Water as a Relationship
Write 3–4 sentences responding to this prompt:
"In Māori worldview, wai (water) is not a resource — it is a living being with mauri, and those who draw from it are in a relationship with it. What would it mean to be a kaitiaki of wai in the design of a water system? What would a designer be obligated to protect, restore, or refuse?"
Your entry should name one specific thing your water system design does that a kaitiaki of wai would approve of, and one thing that a kaitiaki might still question. It may be that your design is not yet answerable to kaitiakitanga in full — if so, say what is missing.
Exit Claim | Whakamutunga (4 min)
On a slip of paper (anonymous, collected at the door):
"One thing my water system design does well is ______. One thing it still can't solve is ______."
Teacher use: Look for genuine limitations — not "nothing" or "it solves everything." The best responses will name structural constraints (no mains backup, storage cost, contamination risk in greywater reuse) and show that students understand a design addresses some problems while leaving others unresolved. Water technology does not eliminate the need for infrastructure investment, regulation, or cultural governance — it complements them.
Kaiako Planning | Ngā Tūāhu Whakaaro
📋 Curriculum Alignment
This lesson addresses the NZ Curriculum Technology strand: Technological Practice — Brief Development and Planning. Students design a technological system for a specific context with identified constraints and criteria — the core brief-development competency. The Māori relationship with wai addresses Te Mātaiaho's emphasis on mātauranga Māori as an equal partner to Western science in understanding the natural world.
Science connections: Planet Earth and Beyond — the water cycle, freshwater systems, water quality parameters. Social Sciences: Aotearoa New Zealand Histories — Māori land and water rights, Treaty settlements, the Waikato-Tainui river settlement as contemporary governance example.
📦 Materials & Resources
- If available: a simple rain gauge — measuring local rainfall makes the rainwater harvesting calculation concrete
- Printed or projected context cards for the design challenge
- Paper slips for exit claims
- Optional: actual greywater diversion system diagram (available from Auckland Council or BRANZ building science resources — free online)
NZ-specific resources: The Waikato River Authority website (waikatoriverauthority.govt.nz) documents the cultural and governance framework for the river. BRANZ (branz.nz) has free technical guides to rainwater harvesting and greywater systems compliant with NZ Building Code — useful for teachers wanting technical accuracy in the design challenge.
🔄 Differentiation
For students who need more support: Provide a partially-completed design template for Context B (school) with the rainwater harvesting system already selected. Students complete the four questions rather than choosing the system. Provide the rainfall-to-tank-size formula: Roof area (m²) × Rainfall (mm) × 0.8 (loss factor) = litres collectible per mm of rain.
For students who move faster: Research the 2016 Havelock North water contamination event — campylobacter entered the reticulated supply and 5,500 people became ill, with four deaths. What design failures enabled this? What changes were made? What does this tell us about the trade-off between centralised system efficiency and resilience?
For students interested in engineering: First-flush diverters are a simple but elegant engineering solution to roof-collected water contamination. How do they work? What volume of first-flush should be diverted to remove most contamination from a typical 100m² roof? (Answer: approximately 1 mm of rainfall × roof area ÷ 1,000 = litres to divert — typically 10–15 litres.)
⏭️ Next Lesson Connection
Lesson 18 (Agritech: Vertical Farming and Sustainable Food Systems) moves from urban infrastructure water to agricultural water — the largest freshwater use in Aotearoa (approximately 80% of water allocation). Students will see how precision irrigation technology connects to the water kaitiakitanga obligations from this lesson: water technology in agriculture is not just about efficiency, but about the relationships between water, soil, kai, and the communities that depend on them.