Groundwater

What is groundwater?

Groundwater is water that has travelled through the soil to underground aquifers - areas of fractured rock or porous sediments such as sand or gravel.

Groundwater in Northland

Northland's groundwater is generally in good condition and is an important source of water for communities, agriculture, and ecosystems. Groundwater supplies drinking water, supports farming and horticulture, feeds springs and streams, and helps rivers keep flowing during dry periods. The biggest future risks are climate change, drought, increasing demand, and saltwater intrusion into coastal aquifers. 

Where does groundwater come from?

Groundwater in Northland generally comes from rainfall soaking into the ground. Winter rainfall is especially important because it helps refill aquifers.

Groundwater then slowly moves through soils and rocks before emerging in springs, streams, wetlands, lakes and the coast.

What is the current state of groundwater?

Overall, groundwater quality in Northland is generally good and most monitoring sites meet New Zealand drinking water standards.

What are the main groundwater issues?

Localised nitrate contamination

Nitrate is the main human-caused contaminant of concern in Northland. It can come from farming, wastewater systems, and other land uses. Elevated nitrate levels are localised rather than widespread.

Saltwater intrusion

Many of Northland's aquifers are close to the coast. During droughts, heavy water use, or sea-level rise, saltwater can move inland and affect groundwater quality. Some coastal aquifers are already showing signs of risk.

Bacteria

Occasional detections of E. coli are usually linked to individual bore construction or maintenance issues rather than contamination of entire aquifers.

Are groundwater levels stable?

Long-term monitoring shows most groundwater sites are stable or increasing over 20 to 30 years, but droughts such as the 2018-20 drought can cause significant short-term declines. Shallow coastal aquifers are vulnerable to climate change and sea-level rise.

How much groundwater is being used?

Northland has many important aquifers, including:

• Aupōuri
• Glenbervie
• Kaikohe
• Mangawhai
• Ruawai
• Russell
• Numerous small coastal aquifers  

Some aquifers are already fully allocated, meaning there is little or no capacity for additional groundwater takes.

What do we know about our aquifers?

Council has completed several studies on Northland's aquifers and published the findings in technical reports.

One of the latest projects is the 3D mapping of the Te Hiku Peninsula (Aupōuri Aquifer). 

What is the outlook for groundwater in Taitokerau?

Northland's groundwater remains a valuable and generally healthy resources, however, future challenges include:

• Longer and more severe droughts
• Increasing water demand
• Sea-level rise
• Saltwater intrusion risks
• Pressure on highly allocated aquifers  

Continued monitoring, efficient water use and careful management will be important to protect groundwater for future generations.