The latest official stocktake of the state of New Zealand’s freshwater carries many of the headline messages we have come to expect.

Pressures such as intensive land use and climate change are continuing to degrade our lakes, streams and rivers, with pathogen contamination making many monitored sites unsafe for swimming.

The country’s vulnerable freshwater habitats are struggling with stresses that range from nutrients and invasive species to warming water temperatures.

And once again, the Ministry for the Environment and Stats NZ’s new report, Our Freshwater 2026: Tō Tātou Wai Māori, underscores just how central freshwater systems are to our wellbeing. They support our health, help produce our food and energy, and sustain ecosystems.

What sets this latest report apart from others before it, however, is its focus on a part of the water cycle that is largely out of sight – but nonetheless crucial.

A hidden system with a long memory

Groundwater is what fills the pores and fractures of sediments and rocks beneath our feet, sometimes just a few metres down, and in other places hundreds of metres below ground.

It is core source of water for agriculture and provides drinking water to nearly half the population. During dry periods, it maintains the flow of rivers by slowly releasing water stored in aquifers.

Groundwater can also act as both a sink and a pathway for contamination. Once nutrients and other pollutants enter groundwater systems, they can linger within........

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