Porirua Harbour Trust

Discover the Harbour

Overview and maps

 Geography of the Porirua Harbour and Catchment.

Location

Porirua Harbour is located on the southwest coast of New Zealand’s North Island, approximately 21 kilometres north of Wellington City. This large estuary is surrounded by the city of Porirua and many of its suburbs, including Titahi Bay, Elsdon, Aotea, Papakōwhai, Paremata, Plimmerton, Whitby and Pāuatahanui Village.

The harbour lies where State Highway 59 meets the sea, forming a key part of the Wellington Region. It consists of two main arms — the Pāuatahanui Inlet and the Parumoana (or Onepoto) arm — both of which were once thriving ecosystems rich in marine and bird life.

Harbour Geology

Porirua Harbour was formed between 15,000–10,000 years ago, when sea levels rose by 120 meters, flooding the land and river valleys flowing westward to the coast. The area sits on the active boundary between the Australian and Pacific tectonic plates, and three major fault lines — the Ohariu, Pukerua, and Moonshine faults — run through the region in a northeast-to-southwest direction. More information on the geology is found here.

The Porirua Harbour Catchments

The Porirua Harbour catchments encompass the entire area that drains into the harbour — stretching from Pukerua Bay in the north to the Wellington City suburbs of Johnsonville, Churton Park, Paparangi and Newlands in the south.

To explore where your local stormwater flows, view the Porirua Harbour Catchments Map, which shows the network of streams and feeding into the harbour.

Harbour Entrance

The harbour entrance receives water via the Tāupo Stream catchment, originating in Pukerua Bay. Water from Pukerua Bay, Plimmerton, and surrounding farmland flows through Tāupo Swamp before reaching the sea at the southern end of Plimmerton.

The Pāuatahanui Inlet is the larger of the harbour’s two arms and is fed by four main streams:

  1. Kakaho Stream – flows through farmland north of the inlet, crossing Grays Road.
  2. Horokiri Stream – runs beside Paekākāriki Hill Road, through Battle Hill Farm Forest Park, and into the wetlands at the head of the inlet.
  3. Pāuatahanui Stream – drains the Haywards Hill, Judgeford, and Belmont areas.
  4. Duck Creek – flows from Belmont, through Whitby, and into the inlet.

The Parumoana (Onepoto) Arm receives water from numerous smaller streams and lagoons around Titahi Bay, Aotea, and Papakōwhai. Key water sources include:

  1. Kenepuru Stream – drains the areas of Waitangirua, Porirua East, and Cannons Creek.
  2. Takapūwāhia Stream – flows from Elsdon.
  3. Porirua Stream – collects water from Johnsonville, Newlands, Churton Park, Grenada, and Tawa via tributaries such as Mitchell Stream (Colonial Knob), Stebbings Stream (Churton Park), and Takapu Stream.

Several lagoons and freshwater lakes lie within the Porirua Harbour catchment:

  • Tidal lagoons — including Aotea Lagoon, Papakowhai Lagoons, and Okowai Lagoons — were formed during motorway construction in the 1960s and later urban development. These collect stormwater from the Aotea, Papakōwhai, and Paremata areas.
  • Freshwater lakes — include Whitby Lakes, the Police College lake, and Okowai Lake

Urban Development and Environmental Impact

Urbanisation brought further changes. Roads, railways, and land reclamation altered the shoreline and reduced the harbour’s tidal prism — the volume of water flowing in and out with the tide.

The catchment areas surrounding Porirua Harbour have experienced rapid population growth since the 1940s, rising from fewer than 1,000 residents to 20,000 in 1965 and 61,500 in 2025