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.

  • (no image provided)

    Conceptual models

    We've developed conceptual models for each of our study species. These models describe our current understanding of the factors influencing their distribution and abundance in the Te Arawa lakes, as well as the relationships between the various factors.
  • Sustainable management framework for Te Arawa Lakes customary fisheries

    Research Project
    NIWA and the Te Arawa Lakes Trust have developed a sustainable management framework for customary fisheries in Te Arawa lakes, as part of a joint 3 year research programme.
  • Freshwater

    Freshwater Update

    Publication series
    A regular newsletter with updates on New Zealand's water resources and NIWA's latest freshwater research.
  • Estuary monitoring by communities

    These guidelines outline a recommended minimum set of methods for a community group interested in following habitat changes in an estuary.
  • (no image provided)

    Estuaries publications

    Where an online version is not available, a PDF is provided. Use your browser’s Back button to return to this page.
    Bell, R.; Green, M.; Hume, T.; Gorman, R. (2000). What regulates sedimentation in estuaries? Water & Atmosphere 8(4): 13–16.
    Davies-Colley, R.; Nagels, J.; Donnison, A.; Muirhead, R. (2004). Flood flushing of bugs in agricultural streams. Water & Atmosphere 12(2): 18–20.
    Green, M. (2003.) The dance of the turbid fringe. Water & Atmosphere 11(2): 20–21.
    Green, M.; Ellis, J.; Schwarz, A.-M.; Lind, D.; Bluck, B. (2003).
  • (no image provided)

    Resource Management Act

    The Resource Management Act 1991 (RMA) dictates how we are to manage our physical environment, including the coast and estuaries.
  • (no image provided)

    Models

    A model is a representation of a “real thing”. Usually, the model is simpler in some or many ways than the real thing; the model simulates the behaviour of the real thing; and the model can be used to predict the future behaviour of the real thing.
  • (no image provided)

    Monitoring

    Monitoring is often an expensive exercise, but it does not have to be.
  • (no image provided)

    What now?

    Estuaries are more than just the mudflats that we cross on the way to the beach. Of course they have intrinsic value – what natural environment doesn’t? – but they also provide us humans with a range of ecological services that help to sustain the quality of our environment, and with amenities that we all enjoy, and sometimes profit from.
  • NZ estuaries

    Over the past decade, NIWA has published many popular articles that deal with estuaries - this overview is intended to bring together and make whole sense of the information published to date in the various popular articles.
  • (no image provided)

    The life of an estuary

    An estuary is a semi-enclosed embayment, with a free connection to the sea at one end and a freshwater supply at the other.
  • (no image provided)

    Salmonidae

    Salmon, Trout and Char (Salmonidae) The Salmonidae family is native to the Northern Hemisphere, but several species have been introduced to New Zealand. Some of these species, particularly brown and rainbow trout, have established very successfully here and support New Zealand’s reputation as an angling Eldorado.