Example of a bore.Example of a bore.

Groundwater is water that exists beneath the earth's surface. The quantity and quality of groundwater largely depends on the underground rock formation within which it is contained, e.g. sand, gravel, fractured volcanic rock.

In Northland, the main aquifer systems are contained in basalt rock, like Whāngārei and Kaikohe, or in the Aupōuri sands. Rainfall is the main groundwater recharge source for these aquifers.

The council monitors groundwater in Northland using three main methods:

· State of the Environment (SOE) monitoring to record the general state of groundwater quality and quantity, and change over time (trends);

· Monitoring of activities that may affect groundwater to prevent or minimise any adverse effects caused by these activities; and

· Investigating individual aquifers where specific problems have been identified.