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Auckland Council

Freshwater report card, Great Barrier reporting area 2016

Area grade: A

What makes up this grade?

The overall grade is made up of five indicators:

Water quality: Water samples are tested for temperature, oxygen concentration, turbidity and the levels of pH, ammonia and nutrients (nitrogen and phosphorus). The results of this testing are compared against guidelines for Auckland to produce a water quality index.

Flow patterns: This involves monitoring the hydrologic connectivity of the river to upstream and downstream reaches and the floodplain using the Stream Ecological Valuation (SEV), which is a method of assessing the ecological health of our rivers.

Nutrient cycling: This involves monitoring the inputs and processing of minerals, particulates and contaminants using the SEV biogeochemical functions.

Habitat quality: This involves monitoring the diversity and quality of habitats using the
SEV habitat provision functions.

Biodiversity: Field assessments and samples are collected to assess the type and amount of native plants and animals using the SEV biodiversity functions.

Quick facts

The reporting area consists of Great Barrier Island and Little Barrier Island which cover 320KM2 OF LAND representing 6.5% of the region
the reporting area has the largest native vegetation (92%) of any of the reporting areas
The extent of impervious surface (hard surfaces) is likely to be lower than the regional average of 9%

Monitoring background and interpretation

Auckland Council’s State of the Environment (SoE) monitoring programme has been building a record of Auckland’s environment for more than 25 years. This information is critical to the effective management of Auckland’s natural environment, after all, you can’t manage what you don’t monitor.

The monitoring programme shows there is a strong relationship between the health of rivers and the type of land cover in the surrounding catchment. Rivers that drain through forested catchments (particularly native forests) typically have excellent water quality and ecology, while rivers that drain from urban catchments typically have poor water quality and ecology.

The Great Barrier reporting area is predominantly forested and as a result the health of the area’s rivers is likely to be excellent.

Rivers in this reporting area tend to have riparian margins with lots of trees and bush, which provide shade, leaf litter and woody debris to the stream and anchor the stream banks. The absence of urban development means there is very little channel modification or pollution from discharges or stormwater.

The data used to produce this report card is from:

​River name​Site location​Measurements​Date range
​Native forest average*​Water quality​2014-16
​Kaiaraara Stream​DOC hut​SEV​2014
​Kaitoke Creek​Hot Springs Track​SEV​​2014
​Karaka Bay Stream​Karaka Bay Road​SEV​​2014
​Mabey Stream​Mabey Road​SEV​​2014
​Rarohara Bay Stream​DOC reserve​SEV​​2014
​Tryphena Stream​Medland Road​SEV​​2014

* It is impossible to monitor every characteristic of every freshwater environment, hence for some areas, such as Great Barrier, we monitor ecological health but have used results from similar catchments to infer water quality.