Sources
| Source | What it provides | Terms |
|---|---|---|
| LAWA and Waikato Regional Council | Every water-quality measurement: thirteen sites on the river, sampled monthly, January 2004 to December 2024. River water quality monitoring data, North Island 3 of 3, published 9 February 2026. | CC BY 4.0 |
| NIWA / Earth Sciences New Zealand — REC2 | The river network that every distance downstream is measured along, and its elevations. | CC BY-NC 4.0 |
| Stats NZ | Estimated resident population of every settlement on the river, June 2025. | CC BY 4.0 |
| OpenStreetMap contributors | The map; the river the journey follows — the Waikato (relation 2751038), the Tongariro (relation 18122690) and the streams off Ruapehu; and where each settlement is. | ODbL |
| OpenMapTiles and OpenFreeMap | The vector tiles the map is drawn from, restyled here. Served live from OpenFreeMap. | OpenMapTiles schema; OSM data under ODbL |
| Waikato Regional Council | Mean and extreme flows at four gauges on the lower river, read 2026-09-18. | No terms published |
| Bill Vant, Waikato Regional Council, quoted by RNZ | Where the river’s nitrogen comes from: 61% from land use, mainly pastoral farming; 6% from town and industrial wastewater; 33% background. | Quoted and attributed |
| Bill Vant, Waikato Regional Council — Technical Report 2015/13 | What takes the river’s clarity: algae about half the loss between the Taupō gates and Ngāruawāhia; below it, suspended silt about twice as important as algae. Visual clarity of the Waikato and Waipā Rivers, March 2015. | Quoted and attributed |
| Waikato Regional Council — Technical Report 2018/44 | That the river’s algae are limited by its nutrients — the link between the nitrogen and phosphorus and the clarity. Nutrient limitation of algal biomass in the Waikato River. | Quoted and attributed |
| Watercare | Up to 225 million litres a day drawn from the river near Tuakau for Auckland (14 July 2021). | Quoted and attributed |
| Parliamentary Counsel Office | The Waikato-Tainui Raupatu Claims (Waikato River) Settlement Act 2010 and Te Ture Whaimana, quoted on the journey. | CC BY 4.0 |
Each stop on the journey names its own sources under its passage: NZHistory, Te Ara, the Department of Conservation, NIWA, Waikato Regional Council, the Parliamentary Commissioner for the Environment, Mercury, Ngā Taonga, Living Heritage and Love Taupō among them.
REC2 is offered for non-commercial use only, so this site is non-commercial and has to stay that way while it is built on it. Data sourced from LAWA (Land, Air, Water Aotearoa) and Waikato Regional Council, available under the Creative Commons Attribution 4.0 International Licence.
How the comparison is made
Distance
Every measurement, settlement and dam is placed on one axis: kilometres downstream along REC2’s mainstem, 444 km from Ruapehu to the sea. The journey starts at REC2’s head, on the ice 2600 m up, and follows OpenStreetMap’s streams and river, which the map is drawn from, wherever they are mapped; across Lake Taupō it takes a curve clear of the island, and for the last 14 km, where OpenStreetMap maps the estuary only as water, it follows REC2’s line, smoothed. Every point is filed under the same kilometres, and the two surveys agree on the river’s length to within 1%.
People
A settlement counts as on the river if its centre is within 3 km of the channel. 14 of them are within 1.2 km and not in question. Tuakau is in at 2.95 km, and Te Kōwhai (5.79 km), Te Kauwhata (3.65 km), Pōkeno (3.20 km) are out — so the line does matter at its edge. Counting Pōkeno, 7,380 people, would move the lower Waikato from 10% of the river’s people to 12%. That gives 269,700 people. Living near the river stands in for using it; nothing here counts visits.
Nutrients and clarity
Medians of every sample at each of the 13 sites, 2004 to 2024: total nitrogen and total phosphorus as multiples of the Taupō control gates, and clarity as the distance a black disc stays visible through the water. The gates have no clarity record, so clarity starts at Reids Farm, 900 m on. These are concentrations, not loads: the river grows downstream, and the lower reach carries more nutrient by weight than its concentration rise alone suggests. That clarity falls as the nutrients rise is what the sites show together; why is Waikato Regional Council’s finding, and it is part algae and part silt.
Colour
Nobody measures the river’s colour. The colour of the line on the map and of the water in the chart is keyed to the clarity reading — blue where it is clear, green, then brown as it closes in — following what WRC finds takes the clarity: algae above Ngāruawāhia, silt below. The chart’s lines and the map’s colour are drawn as smooth curves between sites, because the water changes along the river rather than at the stations; the curves never go beyond the readings either side, and every number in the panel is one site’s reading. Below Tuakau, where nobody measures, the line keeps Tuakau’s colour: there is no reading, and no reason to draw the water any clearer.
Dedication
This is for the people who look after the Waikato.
For the field staff who go out to the river every month so there is a record going back decades. For the people in the labs who run the samples, the scientists who make sense of them, and everyone at LAWA, Waikato Regional Council, NIWA and Stats NZ who publishes what they find so that anyone can use it. For the river iwi, who are its kaitiaki and share in its care. And for the people who write the region’s environmental policy, trying to do right by everyone who depends on the river, in work that is slow, contested and rarely thanked. Every number on this site is theirs.
And for my wife, who has spent more than twenty years in environmental monitoring and policy. It isn’t always easy, and you do it to make a difference. It does. I see it, and I hope you feel seen.