On 1 July 2025, NIWA merged with GNS Science to become Earth Sciences New Zealand.

Freshwater

We provide public information on river, lake, and groundwater conditions across New Zealand including freshwater quantity and quality.

Rachel Crawford and Paul Franklin inspecting a fish passage on the Waikato River.

Freshwater and Estuaries Update

A seasonal review and outlook for New Zealand's water resources, and an update on NIWA's freshwater research

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    Common hydrological terms

    Education Resource
    Descriptions of the common terms that explain the processes that occur in hydrology.
    River flow forecasting

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    Tuna - tuna heke (downstream migrants)

    Once eels become migrants (also known as tuna heke or tuna whakaheke) they stop feeding, and progressively develop the external features that clearly distinguish them from 'feeders'.
    Freshwater

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    Horticultural activities

    Land is tilled, sowed, and harvested for horticultural crops to grow.

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    Nutrients and wastewater

    How do nutrients from wastewater treatment enter waterways?
    Freshwater quality

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    Coralline Algae

    This identification guide covers the common crustose coralline algae found in central New Zealand.
    Algae
    Coral

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    New Zealand rushes (Juncus): factsheets and key

    New Zealand rushes (Juncus): species-level factsheets.

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    Proud of your plants? 1 June 2017

    News article
    01 June 2017
    NIWA is doing a nationwide study to discover what makes the best riparian projects. Help us give you the knowledge to make the best riparian management decisions possible by taking our 5 minute survey.
    Rivers
    Freshwater quality

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    Mangroves: to clear or not to clear?

    Media release
    19 May 2017
    NIWA scientists have written a guide for managing mangroves, prompted by a desire for people to learn more about mangrove ecosystems, and what happens when they are removed.
    Estuaries
    Mangroves

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    NIWA Technical Background report for MfE “Clean Water” Swimmability Proposals for Rivers

    News article
    11 May 2017
    NIWA provides technical background information on "Clean Water" swimmability proposals.
    Freshwater quality

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    Paradise for eels? Getting to know the secrets of NZ's new icon

    Feature story
    09 May 2017
    As New Zealand's "Mr Eel", Niwa's Dr Don Jellyman has heard every tall tale. And some of them may be true.
    Estuaries
    Fisheries

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    Wetlands

    Wetland species and wetland management in New Zealand.
    Wetlands

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    Ten years of willow control at Whangamarino Wetland 1999 - 2008

    NIWA review of the ten year Whangamarino willow control programme and evaluation of willow distribution and other wetland vegetation types.
    Wetlands