Specific groundwater investigations

 

Aquifer systems

The Council undertakes a specific groundwater investigation where a potential issue has been identified, e.g. elevated nitrate or increased risk of saltwater intrusion in coastal areas. High salinity may be associated with saltwater intrusion in low-lying coastal aquifers (the movement of saltwater into fresh groundwater). There are currently five aquifers in Northland that are subject to further investigation – Ruawai, Taipā, Maungakaramea, Russell and Whatitiri.

Photo: Well constructed bore

Ruawai and Taipā

Important for: irrigation, stock and public drinking water supply.

Issues: water quality degrading and risk of saltwater intrusion.

Test results: Ruawai six bores are currently monitored for saline indicators, bacteria and iron on quarterly basis. The results of sampling during 2009-2010 indicate no significant changes in water quality but chloride, sodium and iron concentrations remain elevated. Taipā: four bores were sampled on quarterly basis for chloride and nitrate levels. During 2009-2010, there was no significant variation in chloride or nitrate concentrations. Nitrate concentrations are below the NZ Standard but elevated in two sites and the Council will continue to monitor.

Russell

Important for: domestic use.

Issues: risk of saltwater intrusion.

Test results: Four bores are currently monitored for saline intrusion on monthly and quarterly basis. The results of monitoring undertaken during 2009-2010 show no significant change in water quality and no increase in saltwater intrusion in Russell.

Maungakaramea

Important for: domestic use, stock drinking water and irrigation.

Issues: elevated nitrate concentration in groundwater.

Test results: Four bores are currently monitored in Maungakaramea on monthly basis.

The results from the 2009-2010 period indicate a reduction in nitrate concentrations in three bores and an increase in one. The concentrations are still elevated but remain under the New Zealand drinking water standards of 11.3 mg/L-N. The Council will continue to monitor.

Whatitiri

Important for: horticulture, stock drinking water.

Issues: elevated nitrate concentration in groundwater.

Test results: In collaboration with Waimarie Marae Based Nursery, six bores are currently being monitored for nitrate levels. The results of monitoring undertaken during 2009-2010 indicate elevated nitrate levels in two bores, potentially as a result of fertiliser application and land use changes. The results are still under the health-related drinking water guideline and the Council will continue to monitor and investigate.

Age Testing

During 2009-2010, eight bore sites were sampled to determine the average age of groundwater. Understanding the mean age of groundwater is important for interpreting the water quality results and the potential effects of land use on groundwater quality. Results not available at time of publication.