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Groundwater is rainwater that has travelled through the soil to underground aquifers. It makes up about 90 percent of the region’s fresh water resource. Aquifers are areas of fractured rocks or porous sediments such as sand and gravel.

Wells pump groundwater from aquifers. We use it for drinking, in industry, agriculture and horticulture.

Around half of our region’s rural population rely on groundwater for drinking.

Groundwater flow

Rainfall naturally replaces water pumped from aquifers. The amount of water in our aquifers will sustain our needs as long as we don’t take too much. Recent years have seen large increases in the amount of surface and groundwater used in our region.

When too much groundwater is taken from aquifers:

  • The level of groundwater left in aquifers lowers (lowering of the water table).
  • There may not be enough water for everyone to use, resulting in competition for water.
  • Less groundwater flows into streams - during extended dry periods most of the water present in a stream may be from groundwater.
  • Land may subside.
  • In coastal areas salt water may come into freshwater as the water table drops.

Groundwater quality

Contamination of groundwater can occur when substances make their way down through the soil into the underlying aquifers. This generally happens slowly and may not be noticed for some time, but once groundwater is polluted it is very difficult to clean up. That’s why it’s so important to protect and monitor our valuable groundwater resource.

Contaminants in our groundwater come from either point (from specific locations) or non-point sources (from wider areas).

Point sources include: Non-point sources include:
Septic tanks, leaking effluent treatment ponds and landfills Pesticide and fertiliser applications
Leaking underground fuel tanks and pipelines Agricultural land use
Mines and waste tailings Application of wastes to land
Chemical storage areas and timber treatment sites Saltwater intrusion.
Waste disposal sites, such as offal holes.  

In many areas groundwater quality is declining due to:

  • an increase in the amount of waste water discharged onto land – to about 460,000 m3/day
  • increased use of nitrogen fertiliser
  • a doubling of stocking rates over the last forty years - animal waste from intensive farming contaminates groundwater with nitrate.

The nutrients present in groundwater affect the plants and animals that live in the rivers and streams it flows into.

Looking after our groundwater

The way we use our land can have major effects on groundwater quality. To make sure we look after our groundwater supplies, Waikato Regional Council:

  • regulates and monitors point source discharges to land
  • develops voluntary codes of practice to manage non-point sources
  • encourages appropriate land management to reduce negative impacts of land use on groundwater
  • usse environmental education to promote responsible land and groundwater use
  • works with district health boards, district and city councils, and water supply managers to promote appropriate land use near important groundwater supplies and vulnerable groundwater recharge areas.

We also support codes of practice and industry guidelines for:

  • agrichemicals (Growsafe)
  • fertiliser use
  • underground petrol storage systems.