ROTAN is a GIS-based catchment hydrology and water quality model that models the effects of land-use change and nitrogen mitigation measures such as riparian margins and plant uptake on nitrogen export to waterways. This model is based on the Scandanavian HBV and HBV-N models in which soils and aquifers are modelled as a series of fully-mixed reservoirs (buckets) connected in series and parallel. ROTAN has been developed by NIWA and has been used in policy formulation related to the Lake Rotorua catchment.


ROTAN is used for the prediction of nitrate inputs to lakes for various land use, rainfall, and mitigation scenarios.

State of Development Closed Beta
Current Development Activity Nil

Development Contact

Kit Rutherford
+64 7 856 7026
National Institute of Water and Atmospheric Research
c/- NIWA Hamilton Gate 10 Silverdale Road Hillcrest, Hamilton 3216 PO Box 11115, Hamilton, New Zealand

Main Developers

  • National Institute of Water and Atmospheric Research (NIWA)


Outcome Areas Environmental
Management Domains Freshwater
Intended End Users
  • Researcher
  • Regional council and Waikato University
Spatial Resolutions 500-1000m
Spatial Extents Local (i.e. Catchment or District)
Spatial Dimensions 3D
Temporal Resolutions Days, Months
Temporal Extents Days, Months
Steady State or Dynamic Dynamic
Level of Integration Environmental

Input & Output Data

Key Input Data Land Use, Rainfall, Land Cover, Potential Evaporation
Input Data Formats GIS compatible files
Key Output Data Runoff, Drainage water flows and nitrogen concentrations
Output Data Formats GIS Compatible Files


Open/Closed Source Closed Source
Licence Type Unknown
Licence Cost
(Non Commercial)
Not available for non-commercial use
Licence Cost
Not available for commercial use

User Information

Operating Systems MS Windows ArcGIS
Software Needed ArcGIS
User Interface Graphical desktop
Ease of Use Difficult Not intended for use outside the NIWA research group that developed it. Little work done on user manuals, help screens, or internal checking.
Use in Policy Process Plan (Policy Formulation)

Rucinski, D., S. Wadhwa, J. C. Rutherford. (2006). ROTAN - ROtorua and TAupo Nitrate Model. User's Guide. Hamilton, NIWA.

Support None outside NIWA
Users Forum None outside NIWA

Technical Considerations

Programming Language ESRI Visual Basic
Methods included for calibration and validation Calibrated by fitting to measured flows and nitrogen concentrations in streams, and to published annual nitrogen loads entering the lake.
Methods included for managing uncertainty Goodness of fit quantified (RMS error)
Analytical Techniques GIS
Model Structure


Based on the Scandanavian HBV and HBV-N models. Soils and aquifers are modelled as a series of fully-mixed reservoirs (buckets) connected in series and parallel.

Keywords Nitrogen, Land use, Lake, eutrophication
Linkages to other Models
Key References

Nitrogen exports from Lake Rotorua catchment - Calibration of the ROTAN Model.

Associated Case Studies

  • ROTAN - Nitrogen Loads to Lake Rotorua

    This report details a third piece of work in a series prepared for Bay of Plenty Regional Council.  It outlines recent refinements made to the ROTAN model and describes several scenarios of land use change and mitigation.  Findings are intended to help managers develop policy by estimating the extent of export reduction required to meet the lake target of 435 tN/yr and how quickly the load to the lake is likely to respond to such reductions.  The results will be used by the University of Waikato to predict likely changes in lake water quality.

    Read more
  • Other Key Case Studies

    Rutherford, J. C., C. C. Palliser, et al. (2009). Nitrogen exports from the Rotorua catchment - calibration of the ROTAN model. NIWA Client Report, NIWA, Hamilton: 62.

    Rutherford, J. C., C. C. Palliser, et al. (2011). Prediction of nitrogen loads to Lake Rotorua using the ROTAN model. Hamilton, NIWA: 178.

    Rutherford, J. C., A. B. Tait, et al. (2008). Water balance modelling in the Lake Rotorua catchment. NIWA Client Report, NIWA, Hamilton: 47.