WAIORA is a decision support system, developed by NIWA, with particular utility in cases where changes to a flow regime are considered likely to impact on water quality.  It uses information on stream morphology, either from simple measurements at two flows or from a RHYHABSIM dataset, to predict how instream habitat, dissolved oxygen, total ammonia, and water temperature change with flow.  WAIORA calculates the effects of flow on instream habitat, dissolved oxygen, total ammonia, and water temperature, and links the output to environmental guidelines (that can be specified by the user) to determine if an adverse effect is likely to occur. 

Development of WAIORA version 2.0 was funded mainly by MfE and Auckland Regional Council, with contributions from Wellington Regional Council, Hawkes Bay Regional Council, Environment Waikato, Environment Southland and Nelson City Council.


This model provides guidance on whether a water abstraction or discharge to a river could have adverse impacts on dissolved oxygen, total ammonia, water temperature and aquatic habitat.

Latest Version Waiora 2.0.29
State of Development Please Select

Development Contact

National Institute of Water and Atmospheric Research (NIWA)
+64 7 856 7026
Gate 10 Silverdale Road Hillcrest, Hamilton 3216 PO Box 11115, Hamilton, New Zealand

Main Developers

  • National Institute of Water and Atmospheric Research (NIWA)


Management Domains Freshwater
Spatial Resolutions Unknown
Spatial Extents Unknown
Spatial Dimensions Unknown
Temporal Resolutions Unknown
Temporal Extents Unknown
Steady State or Dynamic Unknown

Input & Output Data

Input Data Formats XLS(X)


Open/Closed Source Unknown
Licence Type

User Information

Operating Systems MS Windows
Software Needed Unknown
User Interface Please Select
Ease of Use Unknown

WAIORA User guide (

Technical Considerations

Analytical Techniques Input/output
Keywords Mitigation, streams, habitat

Associated Case Studies

  • WAIORA - Instream Flow Assessment, Horizons RC

    This report addresses options available to Horizons Regional Council for setting defensible minimum flows for rivers in its jurisdiction.  Horizons is currently considering water allocationoptions for the various water management zones within its region, and an appropriate minimum flow is recognised as a key part of the water allocation framework.  However, minimum flow setting is often subject to much debate in policy and resource consent decision making.  At present Horizons have minimum flows set in regional plans for some of its rivers, but aims to incorporate specified minimum flows in the new regional plan (“The One Plan”) to enable debate around minimum flows to occur at the policy level, as opposed to a consent-by-consent basis.

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