9. Lake Quality

Close-up of lake.


RPS objectives

Maintenance and enhancement of lake water quality in Northland to be suitable, in the long term, for aquatic ecosystems, contact recreation, water supplies, aesthetic and cultural purposes.

Reduction in the quantity of contaminants that impact on water quality entering lakes.

Maintenance of the biodiversity of the Northland region.

Protection of the life-supporting capacity of ecosystems through avoiding, remedying or mitigating the adverse effects of activities, substances and introduced species on the functioning of natural ecosystems.

Protection of areas of significant indigenous vegetation and fauna.


· Aquatic weeds are a major threat to Northland's lakes. Some aquatic weeds have already significantly degraded some Northland lakes, such as Lake Omapere and Swan Lake, by growing over the entire area of the lake and preventing the growth of native species.

· There is a strong link between land use type and lake status. Lakes are much more at risk of eutrophication if situated in a pastoral-dominated catchment than in a native catchment.


· The water quality of the Kai Iwi lakes shows little change over time, with Lake Taharoa and Waikere having excellent water clarity and low nutrient concentrations to remain as two of the most pristine lakes in Northland.

· Water quality varies widely over the rest of Northland with signs of eutrophication becoming apparent in some lakes on Aupouri and Pouto Peninsulas.

· Half of Northland lakes that are monitored regularly are eutrophic or worse. The majority of these lakes are situated in highly modified catchments such as pastoral land.

· The ecological condition of 21% of Northland lakes surveyed is outstanding.

Doing well

· The Council has successfully established a Lake Water Quality Monitoring Network, weed surveillance programme and Lake submerged plant indicators (LakeSPI) monitoring programme.

· The Council and Lake Omapere Trustees have developed a Restoration and Management Strategy for Lake Omapere and with huge support from many key stakeholders and the community carried out large amounts of restoration work in the lake catchment.

Areas for improvement

· Protection of lakes from stock having direct access to the lake shores, including fencing and planting of lake margins.

· Protection of lakes from the spread of invasive aquatic weeds.

The Northland region has a large number of small and generally shallow lakes. They were formed either by dune activity, volcanic activity or are artificially made. The dune lakes...
Weeds and pest fish Aquatic weeds are a major threat to Northland's lakes. Native aquatic plant species are generally low growing, and present no management problems. However,...
Water quality The state of a lake can be determined by using the Trophic Level Index (TLI). The TLI uses four key variables, chlorophyll α (indicator of algal biomass), water...
Policy documents The Regional Policy Statement for Northland (NRC 2002) provides an overview of resource management issues in Northland, including those with regard to lake water...
Monitoring The Northland Regional Council will continue to monitor the water quality and vegetation of lakes in the network. Once there is three to four years of data for each lake...
You can help protect Northland's lakes by: · Preventing the spread of aquatic weeds. Make sure your boat, trailer and anchor, drainage machinery, eel nets, diving or fishing gear...
Introduction Lake Swan is 17.4 hectares with a maximum depth of 5.5m, situated near the bottom of the Pouto Peninsula. There is no public access to the lake. The lake has been...
Burns, N., Bryers, G. and Bowman, E. 2000. Protocols for monitoring trophic levels of New Zealand lakes and reservoirs. Report prepared for Ministry for the Environment....
Table 2: Water quality and ecological data for the 31 lakes in the Lake Water Quality Monitoring Network and Lake Omapere including upper NRC sampling site, site location (New...
Published: 03 Apr 2008