9. Lake Quality

Close-up of lake.

Summary

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.

Pressures

· 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.

State

· 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.

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Published: 03 Apr 2008