Marine water quality annual report 2017

Melanie Vaughan
Auckland Council Research and Evaluation Unit, RIMU
Publication date:

Auckland Council operates a long-term, region-wide marine water quality monitoring programme. The main objective of this programme is to gather data to inform the state of the environment trends and reporting as required under section 35 of the Resource Management Act 1991 (RMA). The data are collected to look at long-term trends to identify and monitor water quality changes and to assess the efficiency of council initiatives, policies and strategies. This report documents changes to the monitoring programme and provides a summary of the data collected during 2017.

Marine water quality samples are collected monthly by helicopter, boat and from beaches, and use a combination of field and laboratory analysis to investigate 16 parameters across 32 sites around the Auckland region. Grouped into six geographically distinct sampling runs, the results collected are presented in box plots, displaying the variation in the measured parameters at each site, and in statistical summary tables for each site and parameter.

The data collected under this programme are summarised by a Water Quality Index (WQI), a metric which integrates multiple types of data to assign a water quality class of excellent, good, fair, marginal or poor. This analysis combines water quality measures and compares them against selected “reference” sites to provide a readily understood description of the water quality for the site. For the 2017 reporting year, the method of calculating WQI has changed to account for the variation between open coast and estuarine environments, and to standardise the objectives that the water quality data is compared to. A further change for 2017 data is that the WQI is now grouped into five classes (excellent, good, fair, marginal, poor), rather than the previous four (excellent, good, fair, poor).

In 2017, WQI decreased at seven sites compared to 2016 results. The sites with change included Goat Island, Orewa, Hoteo River Mouth, Kaipara Heads, Dawsons Creek, Mahurangi Heads and Chelsea.

Auckland Council technical report, TR2019/003

Last updated: 2019-04-15