INCA-N (Integrated Catchments Model - Nitrogen dynamics)

INCA-N operates at a daily time step, tracking the stores and fluxes of water, nitrate and ammonium in both the land and in-stream phases of a river catchment. The model is spatially ‘semi-distributed’: the water course is split into reaches with associated sub-catchments. Two spatial set-ups are possible – the traditional set-up, in which there is a single main stem, or a ‘branched’ set-up. The latter allows in-stream processes, effluent inputs and residence times in tributaries to be simulated, and can be particularly useful in larger catchments or complex river networks. Each sub-catchment is split into landscape classes – there can be as many of these as desired or warranted by the data resolution or needs of the study. Landscape classes are “functional units” and within each unit N inputs, plant N uptake, soils and flow pathways should be similar, though for convenience classes are often based on land use and/or soil type. All land-based processes are calculated for a generic 1 km2 cell for each landscape class within each sub-catchment. Water, nitrate and ammonium outputs from the 1 km2 cell for each land class are multiplied by the land class area, and summed to provide total inputs from the sub-catchment to the reach. These inputs are assumed to enter the stream reach directly, rather than being routed spatially from one land class to another. Reach inputs are therefore from the land phase and from any upstream reaches.

Andrew Wade, University of Reading
Release Date
07 October2015
INCA-N is freely available for non-commercial use and can be obtained under license for commercial applications
Operating Requirements
INCA-N is a 32-bit Microsoft Windows application written in C++. It is available as a command-line version (1.09 MB) or with a graphical user interface (3.47 MB), and will run on Windows XP onwards. The RAM required during simulation depends on the application set-up (number of reaches and landscape units) and application period (number of time steps). A simple one year, single reach set-up requires 6.6 MB of RAM.
Application Type
User Interface
Microsoft Windows, Graphical User Interface, control files
Support Available
Limited support from model developers
Application Scale
Geographical Restrictions
Temporal Resolution
Spatial Resolution
River reach and sub-catchment with structure designed by user
Primary Purpose
Estimate inorganic nitrogen loss at different timescales in response to environmental change and catchment management
Key Output Variables
Stream flow, nitrate and ammonium concentrations and loads, nitrogen process loads, soil water and groundwater nitrate and ammonium concentrations
Key Input Variables
DEM, climate data, land use, fertilizer application rates, sewage effluent concentrations, atmospheric N deposition
Calibration Required
Needs target data (flow , sediment and phosphorus concentrations) for optimization and relies on literature values and expert judgement to set parameter values
Model Structure
Dynamic, conceptual, time-series, deterministic
Model Parameterisation
Derived from observation, literature values and expert judgement
Input Data Available on CaMMP Catalogue

Key References

  • INCA-N model description and example application Wade, A.J., Durand, P., Beaujouan, V., Wessel, W.W., Raat, K.J., Whitehead, P.G., Butterfield, D., Rankinen, K. and Lepisto, A. (2002) A nitrogen model for European catchments: INCA, new model structure and equations, Hydrology and Earth System Sciences, 6, 559-582.
  • Whitehead, P.G., Wilson, E.J. and Butterfield, D. (1998) A semi-distributed Integrated Nitrogen Model for Multiple source assessment in Catchments (INCA): Part I - Model Structure and Process Equations. Science of the Total Environment, 210/211: 547-558.
  • Whitehead, P.G., Wilson, E.J., Butterfield, D. and Seed, K. (1998) A Semi-distributed Integrated Nitrogen Model for Multiple source assessment in Catchments (INCA): Part II Application to large River Basins in South Wales and Eastern England. Science of the Total Environment, 210/211: 559-583.

Input Data

  • CHESS – 1 km2 grid of UK precipitation and air temperature
  • British Survey of Fertilizer Practice
  • CEH Land Cover 2007
  • 50m Digital Elevation Model
  • Agricultural Census Data
  • EU FP6 ENSEMBLE climate predictions
  • Sewage effluent data
  • Observed river flows and stream water nitrate an

Output Data

  • Daily time series of Flow Stream water nitrate concentration Stream water ammonium concentration
  • nitrate and ammonium

Quality Assurance

Developer Testing
Internal Peer Review
External Peer Review
Use of Version Control
Internal Model Audit
External Model Audit
Quality Assurance Guidelines and Checklists
Periodic Review