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Porirua Harbour and catchment programme

http://www.gw.govt.nz/porirua-harbour-and-catchment-programme

Porirua Harbour and catchment programme

Updated 19 May 2016 5:42pm


Greater Wellington Regional Council is working in partnership with Porirua City Council, Wellington City Council, Ngati Toa Rangatira, and eight other agencies to address the issues of sedimentation, pollution, habitat loss and restore the environmental health of Porirua Harbour.



Porirua Harbour

Porirua Harbour is the largest estuary system in the lower North Island. It has a nationally significant wildlife area and has cultural, recreational, economic, and ecological value. The Porirua catchment covers an area of 18470 ha and is a mix of rural farmland, lifestyle blocks, urban settlement, parkland, railway line and roads.

The Porirua Harbour is the no.1 coastal area in the GWRC biodiversity ranking system. It is a significant nursery for fish, hosts a range of coastal and wetland birds and has one of the largest cockle concentrations in New Zealand. Seagrass and saltmarsh habitats of regional importance are also found in the Pauatahanui Arm of Porirua Harbour.

Issues

Urban and rural development in the Porirua catchment over the past 150 years has had a big impact on the health of the two estuaries that constitute Porirua Harbour. Urban expansion, stormwater/sewer infrastructure, forestry, rural intensification and roading continue to negatively affect the harbour ecology.

The Porirua Harbour and Catchment Strategy and Action Plan identifies three key issues facing this valuable environment:

  • excessive sedimentation rates
  • pollution
  • ecological degradation

Research

Currently, we monitor estuary sediment quality and health every year to understand the natural variation within the environment and the impacts of human activities. Our priority research areas are measuring sedimentation rates, identifying the main sources of sediment and modelling where that sediment settles in the harbour.  This information will tell us which land-based activities contribute the most sediment and help to develop targeted solutions.

To assist with this we have installed 18 sedimentation plates throughout the harbour, turbidity sensors at the bottom of the three largest catchments for information on how much sediment is entering the harbour, and we sample water quality at times of heavy rain to track sources of sediment and other pollution.  

For more information on the environmental research happening in Porirua Harbour please contact us at environmentalscience@gw.govt.nz

 

Monitoring sediment health in Porirua Harbour

 

Restoration and community involvement

We are involved in various restoration activities in the Porirua Harbour.  We support Whitireia Park Restoration Group and the good work they are doing.  We help school groups in the park to carry out planting and do other activities like building nest boxes to help provide a safe nesting habitat for little blue penguins.  We are currently developing a restoration project for Te Onepoto Bay and wetland where the community will be involved in the restoration of this significant area.

Pauatahanui Wildlife Reserve has fantastic biodiversity values and we are working with Forest and Bird to assist with their restoration efforts.  This site has had thousands of plants put in the ground during years of planting by members of the local community, school students and corporate groups. We are also committing additional resources for weed and predator control in the Pauatahanui Inlet to support the work that has already been undertaken.

A plan to address sediment entering the harbour from steep erosion-prone land and stream bed erosion is currently underway. This will help prioritise where and how we should work to reduce sediment flows into the harbour. 

For more information on biodiversity work in the Porirua Harbour and catchment please contact us at biodiversity@gw.govt.nz 

 You may be interested in articles on Porirua Harbour in the Kapi-Mana News.

 

ANZ staff help out with planting at Onehunga Bay