Water Allocation Impacts on River Attributes (WAIORA)


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.


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. Results are presented graphically and in tables recording the predictions, input data, and guidelines. These can be printed, or cut and pasted into other applications, as required.

All evaluations can be saved in a Microsoft Access database, providing a record of parameters that were evaluated, details of the location, the proposed flow change, the model parameters that were used, and the predicted environmental changes.

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.

Latest Version Waiora 2.0.29
State of Development Released and updated

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
Intended End Users
  • Regional Council Scientist
  • Researcher
Spatial Resolutions Unknown
Spatial Extents Unknown
Spatial Dimensions Unknown
Temporal Resolutions Unknown
Temporal Extents Unknown
Steady State or Dynamic Unknown
Level of Integration Environmental

Input & Output Data

Key Input Data Flow data
Input Data Formats XLS(X)


Open/Closed Source Closed Source
Licence Type No Licence

User Information

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

WAIORA User guide (http://www.niwa.co.nz/sites/default/files/import/attachments/userguide2.0.pdf)

Frequently asked questions about WAIORA (https://www.niwa.co.nz/our-science/freshwater/tools/waiora/faq)


Technical Considerations

Analytical Techniques Input/output
Keywords Mitigation, streams, habitat


Associated Case Studies

WAIORA - Instream Flow Assessment

This case study addresses options available to Horizons Regional Council for setting defensible minimum flows for rivers in its jurisdiction.