Catchment Contaminant Annual Loads Model (C-CALM)


C-CALM is intended to aid in the planning of stormwater treatment systems and has been developed to be easy to use with minimal set-up and run times and modest data requirements.


The Catchment Contaminant Annual Loads Model (C-CALM) is a GIS-based contaminant load model which operates at the sub-catchment scale. Contaminants modelled are total suspended solids (TSS) and particulate and dissolved zinc and copper.

C-CALM consists of a modelling interface backed by a query library of performance rules for a range of stormwater treatment options commonly found in NZ. C-CALM is supplied as a tool-bar for ArcMap. Users are asked to supply the spatial data needed to run the model; the minimum data required are sub-catchment boundaries and a breakdown of land covers found in each sub-catchment. Users are then able to add treatment options to each sub-catchment; each treatment option is customised for catchment and device characteristics, and the contaminant sources, by filling in a treatment option window.

Treatment options are aggregated, that is, rather than simulating every element in the drainage system, similar treatment devices are modelled as a single device with the same removal efficiency as the individual devices. Rudimentary treatment trains can be simulated by C-CALM with the caveat that C-CALM does not simulate surface flows or device hydraulics, so that the effects of storage and attenuation on treatment are not taken into account. Running the model generates a set of display map layers and a summary table which gives the annual load for each contaminant listed by sub-catchment.

The model was developed by NIWA under sub-contract to Landcare Research as part of the FoRST funded Low Impact Urban Design and Development programme.

Latest Version V2.0 (2014)
State of Development Open Beta
Current Development Activity No current funding for support or development. Available for download on request from NIWA (

Development Contact

Annette Semadeni-Davies
+64 9 375 2050
National Institute of Water and Atmospheric Research
41 Market Place
Auckland Central 1010

Private Bag 99940
Auckland 1149,
New Zealand

Main Developers

  • Landcare Research
  • National Institute of Water and Atmospheric Research (NIWA)


Outcome Areas Environmental
Management Domains Land, Urban Systems
Subdomains Contaminant Losses, Storm Water
Intended End Users
  • Researcher
  • Regional Council Scientist
  • Policy Analyst
  • consultants, developers and decision-makers
Spatial Resolutions Unknown
Spatial Extents Local (i.e. Catchment or District)
Spatial Dimensions 2D
Temporal Resolutions Years
Temporal Extents Years
Steady State or Dynamic Steady State
Level of Integration Environmental

Input & Output Data

Key Input Data Land Use, Land Cover, Rainfall Stormwater treatment
Input Data Formats XLS(X), GIS compatible files
Key Output Data Annual loads of TSS, zinc and copper
Output Data Formats GIS Compatible Files Tables which can exported into Excel


Open/Closed Source Closed Source
Licence Cost
Licence Purchase Contact
Annette Semadeni-Davies

User Information

Operating Systems MS Windows
Software Needed ArcGIS, Excel
User Interface Graphical desktop
Ease of Use Easy Designed for simple set up and use.
Use in Policy Process Plan (Policy Formulation)

 Catchment Contaminant Annual Loads Model (C-CALM 2.0): User Manual. 2014

Support No current funding for support or development

Technical Considerations

Analytical Techniques GIS, Scenario Planning
Keywords stormwater, contaminants, sediment
Linkages to other Models
  • Based on Auckland Council CLM spreadsheet model


C-CALM 2.0 User Manual

Key References

Conference Papers:

Moores, J., and Semadeni-Davies, A. (2011) Integrating a stormwater contaminant load model into a spatial decision support system for urban planning. International Conference of the IWA Diffuse Pollution Specialist Group on: Diffuse Pollution and Eutrophication, 18-23 September 2011, Rotorua, New Zealand.

Semadeni-Davies, A., Moores, J. and Altenberger, A. (2010) C-CALM development and application of a planning tool for stormwater management in New Zealand. 17th Congress of the Asia and Pacific Division of the International Association of Hydraulic Engineering and Research incorporating the 7th International Urban Watershed Management Conference, 22-24 February, 2010, Auckland, New Zealand.

Semadeni-Davies, A., Altenberger, A. and Wadhwa, S. (2009) C CALM – Catchment Contaminant Annual Loads Model. NZWWA 6th South Pacific Stormwater Conference, May 2009, Auckland

Semadeni-Davies, A., Elliott, A.H., Reed, J. (2008) C-CALM: a Catchment Contaminant Annual Loads Model for New Zealand. Presented at 11th International Conference on Urban Drainage, Edinburgh, Scotland.

Associated Case Studies

Other Key Case Studies

Vesely E.-T., Semadeni-Davies, A. and Simcock, R. (2009) Waiarohia catchment stormwater treatment modelling with C_CALM and COSTnz. Landcare Research Contract Report prepared for: Waitakere City Council.

Semadeni-Davies, A. (2009) Simulation of annual contaminant loads from three stormwater catchments to Whangarei Harbour. Report prepared for Northland Regional Council. NIWA client report:AKL2009-064