Groundwater and aquifers
Groundwater is freshwater beneath the surface of the Earth. When it rains or when snow or ice melts, some of the water seeps into the soil and moves downwards into the ground. Groundwater is held in soil pores, in sediments like sand and gravel and in fractured or porous rocks like basalt or limestone. It is a key part of the water cycle and is a valuable natural resource.
Building an aquifer model
In this video, educator Angela Schipper demonstrates how to build a model of an aquifer.
Select here to view the video transcript and copyright information.
Groundwater is used by plants, invertebrates and microorganisms in the soil. For human needs, we usually depend on groundwater that is stored in aquifers.
Aquifers – dynamic freshwater storage systems
An aquifer is an underground layer of water-bearing, permeable rock, gravel, sand or silt that stores and transmits groundwater. Aquifers act as natural freshwater storage systems. These systems are dynamic – they are in slow but constant states of change. Aquifers are fed (recharged) by precipitation and freshwater from streams, rivers and lakes. Groundwater within an aquifer usually moves slowly – at rates of 70–600 mm per day, depending on the type of material (substrate) that makes up the aquifer. Some New Zealand aquifers have faster flow rates, from tens to hundreds of metres per day, but this is still much slower than surface water flows. Groundwater discharges – it naturally makes its way back above the ground – via springs or seeps in rivers or lakes.
Features of an aquifer
There are over 200 mapped aquifer systems in Aotearoa. Every aquifer is unique due to its position in the landscape, the catchment that supplies the water and the substrate that houses it. However, aquifers have some common features.
The ground above an aquifer is called the unsaturated zone. It contains soil water that is used by plants and other living organisms. Freshwater percolates through this zone and into the saturated zone, which is filled by groundwater. The water table is where the unsaturated and saturated zones meet. The water table fluctuates due to water use, groundwater recharge and discharge.
Aquifers can be confined or unconfined. The aquifer pictured in this image is an unconfined aquifer – it is recharged by water percolating directly from above. The water table is the top of the aquifer.
Groundwater storage
Large amounts of water are stored in the ground in pores, cracks and spaces between rock particles. Most of this groundwater storage comes from precipitation that infiltrates into the land surface.
Acknowledgement: Diagram by USGS
A confined aquifer has a layer of impermeable material that traps groundwater underneath it. The impermeable/confining layer prevents the direct recharge of water from the zones above. The top of a confined aquifer is the impermeable substrate that confines it.
Groundwater connections with surface water
Groundwater and surface water – streams, rivers and lakes – are closely connected. When the water table is higher than the surface of a local freshwater body, groundwater seeps/moves in to become surface water. Earth Sciences New Zealand notes that more than 80% of our surface water is supplied by groundwater. When the water table is lower, surface water filters through the unsaturated zone adjacent to the water body and recharges the aquifer.
Te Waikoropupū Springs
Te Waikoropupū Springs are the largest cold-water springs in the southern hemisphere. Eight main vents discharge water from an aquifer beneath the Tākaka Valley. Waikoropupū is the home of Huriawa, one of the three main taniwha of Aotearoa. Te Waikoropupū Springs have been registered as wāhi tapu and are taonga.
Groundwater also becomes surface water via seeps, springs, hot pools and geysers.
Groundwater ecosystems
Aquifers hold more than just groundwater – they also function as ecosystems. Stygofauna are fauna that live in groundwater systems or aquifers. We don’t often see stygofauna because wells and bores are designed to exclude everything but water. Bacteria, fungi, protozoa and metazoa (for example, nematodes and tardigrades) are part of groundwater ecosystems in Aotearoa. There is a lot that we don’t know about our groundwater ecosystems. Earth Sciences New Zealand notes that New Zealand’s stygofauna appear to be “remarkably rich and diverse”. Around 100 species have been named with hundreds more awaiting analysis. Many of the species are endemic to Aotearoa, and several are likely restricted to single aquifers or discrete aquifer systems.
Human interactions with groundwater and aquifers
Groundwater is an important natural resource. It is taonga and vital for our social wellbeing and economic productivity. Around 40% of our drinking water comes from groundwater, from municipal wells in urban areas and bores on private land. Water is also extracted for irrigation purposes – irrigation is the primary reason for freshwater consumption in Aotearoa. Although 80% of the irrigated water used by the dairy industry comes from rivers and lakes, this still has implications for aquifers due to their underground connections.
The ways in which we use the land can impact water quality in our aquifers. Contaminants – toxins from urban activities, septic effluent, landfills and nutrients and pathogens from primary production – can leach into groundwater. Contaminants create both short-term and long-term issues for groundwater and surface water.
Our freshwater – infographic
This infographic is a visualisation of freshwater storage and movement above and below the ground. Changes to one part of this large interconnected system will affect the others as the water flows between them.
Download as a PDF.
The Ministry for the Environment and Stats NZ report Our Freshwater 2026 Tō Tātou Wai Māori notes that, while the median lag time (the time it takes for water from the surface to reach the groundwater) is 4.5 years, some deeper groundwater can take over 100 years to complete a recharge cycle.
Nitrate from fertilisers and animal effluent is of particular concern. It can leach into shallow groundwater, which is then carried into lakes and rivers. Nitrate can also persist in aquifers for decades, leading to water quality issues even after nitrate sources on the land have been reduced.
Related content
Groundwater is a hidden part of the water cycle.
The nitrogen cycle and dairy farming interactive has information about primary production, nitrogen interactions and ground and surface water quality.
Restoring Rotorua’s natural geothermal taonga shows the connection between the geothermal aquifer and Whakarewarewa’s Pōhutu geyser.
Tō tātou wai māori 2026 looks at ao Māori connections with groundwater and the mauri of freshwater as it flows from ki uta ki tai.
Activity ideas
The activity Constructing an aquifer model is a simple visual introduction to groundwater and aquifer systems.
Use similar materials to show how contaminants enter groundwater and surface water through non-point sources and point sources.
Useful links
Groundwater is a key focus of the Ministry for the Environment and Stats NZ report Our Freshwater 2026 Tō Tātou Wai Māori.
Groundwater – not ice sheets – is the largest source of water on land and most of it is ancient, from The Conversation.
Check out the NIWA (Earth Sciences New Zealand) reports on groundwater ecosystems and stygofauna:
