NZ Herald: Manukau Harbour from bad to worse

Date: 30/01/2020

Manukau Harbour from bad to worse as Auckland's coastal areas put under the water quality spotlight
Manukau Harbour's ailing water quality has gone from bad to worse with the latest Auckland Council data showing some areas over 10 times desired nutrient levels.

Environmentalists and nearby residents say the latest report is another indication the harbour has "borne the brunt" of Auckland's wastewater too long, and more needs to be done to turn the situation around.

The annual monitoring report comes just after the Manukau Harbour Forum received a scathing review , finding the body set up in 2010 in response to the harbour's worsening conditions was ill-equipped for the job, mainly due to being underfunded and inadequate resourcing.

It also follows a council environmental scorecard that showed ecology and water quality in the harbour had gone from a D in 2016 to E in 2018.

The Coastal and Estuarine Water Quality: 2018 Annual Data Report analysed water quality at 31 sites across the region's three main harbours: Kaipara, Waitemata and Manukau.

Using the water quality index, measuring a range of key indicators, more than half of the sites assessed had water quality that was "fair" to "good", the best being open coastal east coast sites and the outer Waitemata and Kaipara harbours.

But in the Manukau Harbour five of the eight sites were classed as "poor", with the worst recorded at Mangere Bridge and Waiuku Town Basin. The best sites, Grahams Beach and Manukau Heads, where classed as fair.

Wastewater biologist Gemma Tolich Allen said it was an "ongoing source of disappointment" to see the latest results showing the Manukau Harbour as recording the worst water quality in the Auckland region.

Health grades within Manukau Harbour varied greatly, with sites in the wider harbour where there was more tidal flushing faring much better than others further in, such as Mangere Inlet and Pahurehure.

Parameters such as chlorophyll were seen to be over 10 times council guidelines in some of those inner areas, and phosphorus and nitrogen all showed a high level of exceedance in the northeastern part of the Manukau, closest to the Mangere Wastewater Treatment Plant.

Tolich Allen said under the treatment plant's consent partially-treated wastewater could be discharged during peak storm flows, which happened on average 18-22 times per year.

"These in turn fuel enrichment resulting in the poor water quality. With increasing population growth and increasing numbers of storm events per year as a result of changing weather patterns, this situation is unlikely to improve.

"The Manukau has borne the brunt of Auckland's waste disposal unfairly for too long, land development and stormwater overflows have been insufficiently managed to protect the harbour, and this has resulted in it having the poorest water quality in the region."

Michael Neilson,

General/Maori Affairs reporter, NZ Herald