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New Zealand

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These are a few of the basic questions we can ask about our streams and rivers.

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New Zealand

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The ecology of the river refers to the relationships that living organisms have with each other and with their environment - the ecosystem. An ecosystem is the sum of interactions between plants, animals and microorganisms and between them and non-living physical and chemical components in a particular natural environment.

River ecosystems have:

flowing water that is mostly unidirectional

a state of continuous physical change

many different (and changing) microhabitats

variability in the flow rates of water

plants and animals that have adapted to live within water flow conditions.

Water flow

Water flow is the main factor that makes river ecology different from other water ecosystems. This is known as a lotic (flowing water) system. The strength of water flow varies from torrential rapids to slow backwaters. The speed of water also varies and is subject to chaotic turbulence. Flow can be affected by sudden water input from snowmelt, rain and groundwater. Water flow can alter the shape of riverbeds through erosion and sedimentation, creating a variety of changing habitats.

Substrate

The substrate is the surface on which the river organisms live. It may be inorganic, consisting of geological material from the catchment area such as boulders, pebbles, gravel, sand or silt, or it may be organic, including fine particles, leaves, wood, moss and plants. Substrate is generally not permanent and is subject to large changes during flooding events.

Light

Light provides energy for photosynthesis, which produces the primary food source for the river. It also provides refuges for prey species in the shadows it casts. The amount of light received in a flowing waterway is variable, for example, depending on whether it's a stream within a forest shaded by overhanging trees or a wide exposed river where the Sun has open access to its surface. Deep rivers tend to be more turbulent, and particles in the water increasingly weaken light penetration as depth increases.

Temperature

Water temperature in rivers varies with the environment. Water can be heated or cooled through radiation at the surface and conduction to or from the air and surrounding substrate. Temperature differences can be significant between the surface and the bottom of deep, slow-moving rivers. Climate, shading and elevation all affect water temperature. Species living in these environments are called poikilotherms - their internal temperature varies to suit their environmental conditions.

Water chemistry

The chemistry of the water varies from one river ecosystem to another. It is often determined by inputs from the surrounding environment or catchment area but can also be influenced by rain and the addition of pollution from human sources.

Oxygen is the most important chemical constituent of river systems - most organisms need it for survival. It enters the water mostly at the surface, but its solubility decreases as the water temperature increases. Fast, turbulent waters expose a wider water surface to the air and tend to have lower temperatures - achieving more oxygen input than slow backwaters. Oxygen is limited if water circulation is poor, animal activity is high or if there is a large amount of organic decay in the waterway.

Bacteria

Bacteria are present in large numbers in river waters. They play a significant role in energy recycling. Bacteria decompose organic material into inorganic compounds that can be used by plants and by other microbes.

Plants

Plants photosynthesise - converting light energy from the Sun into chemical energy that can be used to fuel organisms' activities.

Algae are the most significant source of primary food in most rivers or streams. Most float freely and are therefore unable to maintain large populations in fast-flowing water. They build up large numbers in slow-moving rivers or backwaters. Some algae species attach themselves to objects to avoid being washed away.

Plants are most successful in slower currents. Some plants such as mosses attach themselves to solid objects. Some plants are free-floating such as duckweed or water hyacinth. Others are rooted in areas of reduced current where sediment is found. Water currents provide oxygen and nutrients for plants. Plants protect animals from the current and predators and provide a food source.

Invertebrates

Invertebrates have no backbone or spinal column and include crayfish, snails, limpets, clams and mussels found in rivers. A large number of the invertebrates in river systems are insects. They can be found in almost every available habitat - on the water surface, on and under stones, in or below the substrate or adrift in the current. Some avoid high currents by living in the substrate area, while others have adapted by living on the sheltered downstream side of rocks. Invertebrates rely on the current to bring them food and oxygen. They are both consumers and prey in river systems.

Fish

The ability of fish to live in a river system depends on their speed and duration of that speed - it takes enormous energy to swim against a current. This ability varies and is related to the area of habitat the fish may occupy in the river. Most fish tend to remain close to the bottom, the banks or behind obstacles, swimming in the current only to feed or change location. Some species never go into the current. Most river systems are typically connected to other lotic systems (springs, wetlands, waterways, streams, oceans), and many fish have life cycles that require stages in other systems. Eels, for example, move between freshwater and saltwater. Fish are important consumers and prey species.

Birds

A large number of birds also inhabit river ecosystems, but they are not tied to the water as fish are and spend some of their time in terrestrial habitats. Fish and water invertebrates are an important food source for water birds.

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The ecology of the river refers to the relationships that living organisms have with each other and with their environment - the ecosystem. An ecosystem is the sum of interactions between plants, animals and microorganisms and between them and non-living physical and chemical components in a particular natural environment.

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:::: What's It Like Where You Live? ::::

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Streams

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Life in fresh water - Te Ara Encyclopedia of New Zealand

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At the lake's edge, fish find cover among the rocks, while further out tiny zooplankton float and graze. In the river, mayfly nymphs drift downstream, only to be snapped up by a torrentfish. Freshwater habitats seethe with life, from tiny algae to 2-metre eels, and each species is vital to the ecosystem.

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Many Answers entries are not intended to give you the answer but rather guide you to websites and other resources that will help you find the information for yourself.

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Many Answers entries are not intended to give you the answer but rather guide you to websites and other resources that will help you find the information for yourself.

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Where does the water from your home and section go. Within which water catchment does your storm water flow downstream into the harbour.

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Porirua Harbour and catchment programme | Greater Wellington Regional Council

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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.

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Rivers and Streams | Greater Wellington Regional Council

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River and rainfall levels are also available on Hydroline, which are voice mail boxes updated hourly (calls cost 12 cents per minute) - Hutt Valley 08 322 0170, Kapiti Coast 08 322 0150, Wellington/Porirua 08 322 0190, Wainuiomata/Orongorongo 08 322 0650, Wairarapa rivers 08 322 0669 or Wairarapa rainfall and lakes 08 322 9069.

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Harbour Catchment " Porirua Harbour Trust

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Where does the water from your home and section go. Within which water catchment does your storm water flow downstream into the harbour.

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Porirua Harbour Trust " Porirua Harbour Trust

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News View more

November 2021
Storage tank ugly but necessary
A giant wastewater storage tank on Porirua City's front door step will be ugly for the five to seven years it takes to get vegetation established. The Harbour Trust is advocating for a green roof with weeping vines on the structure to aid camouflage as fast as possible. The tank will provide a mechanism to avoid many of the current spills of raw sewage into the harbour so the Trust supports construction of the tank and has said so in a formal planning submission.

October 2021
Planting progress
October 5 was a great post-rain day to get 3000 more plants into the ground by the Kenepuru Darts club. Thanks to Ngāti Toa Rangatira, Porirua City Council and their sponsors plus the volunteers from the community who helped do the mahi.

September 2021
We're looking for a new secretary!
The Te Awarua-o-Porirua Harbour and Catchments Community Trust is looking for a voluntary secretary to help keep the Trust organised. This is an opportunity to join our work advocating for the health of the harbour and its streams. You would be present and involved in many interesting discussions on all manner of issues that impact our mission, preparing agendas and recording minutes for our monthly meetings. The time commitment is self-paced but up to 10 hours a month. A full position description can be found through the PHT secretary link. If you are looking for a way to contribute to the community by using skills and experience please register your interest by emailing phacctsec@gmail.com
AGM and a new chairperson
The Trust held its annual general meeting this month and reflected on a busy year. Two items stood out: The decision in June to formally cease the old trust and transfer its assets to the new Te Awarua-o-Porirua Harbour and Catchments Community Trust. In the same month, the Trust's Education Coordinator, Rebecca McCormack advised that she was leaving Wellington and consequently relinquishing her role after seven highly productive years. The Trust was truly appreciative of the magnificent contribution Rebecca had made in enabling teachers and students alike to participate in the vital goal of improving the health of the harbour and catchments. The Chair of the Trust for the last three years, Mark Neeson, also stood down at the AGM. Mark was thanked for his significant contribution including overseeing and presenting submissions to Council plans relating to the harbour and its catchments, as well as facilitating the transfer of the original trust to a truly independent community trust. Mark's talents will not be lost to the Trust, however, as he will continue serving as a trustee. The new Chair elected at the AGM, is Michael Player. Michael, a former public relations and communications specialist and resident of Papakowhai, has served on the old and current trust for the last two years. In the third change of personnel signalled at the AGM, the Trust's secretary, Lauren James will conclude her service this month. Trust members acknowledged her contribution over several years in helping maintain the efficient conduct of Trust administration. Efforts to recruit a volunteer to fill the secretary role will commence immediately.

For more information on the Trusts' activities over the last financial year check out the annual report.

August 2021
Christine Jacobson joins Harbour Trust
Christine Jacobson of Titahi Bay has joined the Harbour Trust as a trustee this month. Christine, who has impeccable credentials for the role had a career in conservation including previous roles in the Department of Conservation and Porirua City Council. A keen photographer of nature, Christine is also an active member of the Friends of Mana Island.

July 2021

Very "on point" opinion piece by Glen McConnell about science versus the wisdom of mana whenua. He uses the sewage overflows into our harbour and the subsequent rāhui put in place by Ngāti Toa Rangatira as a prime example. https://www.stuff.co.nz/science/300367713/western-science-isnt-keeping-you-safe-from-the-poo-in-porirua

Great news this week when Minister Megan Woods announced significant funding for the redevelopment of Porirua East. This will overhaul the three waters systems in the area, especially replacement of the sewerage pipe in Bothamley Park that regularly overflows into the stream and contributes to ongoing degradation of the harbour. Link to the funding announcement

The Environment Court has delivered a withering criticism of the Gateway Partnership, builders of Transmission Gully, for damage done to the harbour. While the penalties seem modest in the scheme of things, the Judge's commentary confirms what locals who love and use the Inlet know - sediment has built up as a consequence of the TG build...... Environment Court slaps TG road builder with $70k fine

KPMG Review of Strategy

In February 2020 the Porirua City Council received a report from the consultancy firm KPMG entitled Te Awarua-o-Porirua Harbour and Catchment Strategy Review. The following month the Council also received a report from Ngāti Toa entitled: Te Awarua-o-Porirua Harbour and Catchment Strategy and Action Plan. These reports can be found here and here.

Subsequent to receipt of the reports the CE of PCC, Wendy Walker, was made responsible for discussing with all the governance bodies (PCC, GWRC, WCC and Ngāti Toa) a way forward from both reports.

The Porirua Harbour catchment includes all of that area of Wellington and Porirua City where water flows via streams, lagoons and lakes into the Porirua Harbour. This includes the Johnsonville, Churton Park and Tawa catchments that flow down Porirua Stream and its many tributaries; the Whitby, Judgeford, Pauatahanui and Paekaeriki Hill catchments that flow into the Pauatahanui Inlet; the streams in Kenepuru, Elsdon, Porirua East, Takapuwahia and Titahi Bay that flow into the Onepoto Arm; Pukerua Bay and Plimmerton that flow into the Harbour Entrance and Aotea, Papakowhai that flow through the lagoons into the harbour.

Photo Gallery

Stormwater Plaques

Tawa School and Tawa Rotary place "Drain to the Sea" plaques to stormwater drains.

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Cannons Creek School harbour clean up

Cannons Creek senior class cleaning up Onepoto Arm of the Porirua Harbour as part of Love Your Coast month, November 2013.

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Porirua Harbour Trust " Porirua Harbour Trust

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News View more Storage tank ugly but necessary A giant wastewater storage tank on Porirua City's front door step will be ugly for the five to seven years it takes to get vegetation established. The Harbour Trust is advocating for a green roof with weeping vines on the structure to aid camouflage as fast as possible.