Model (UKCEH)
INCA-P (Integrated Catchments Model - Phosphorus dynamics)

INCA-P operates at a daily time step, tracking the stores and fluxes of water, sediment, dissolved and particulate P 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 P inputs, plant P 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, sediment, total dissolved P (TDP) and particulate P (PP) 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.
Version 1.4.11
Andrew Wade, University of Reading
Release Date
06 May 2016
INCA-P is freely available for non-commercial use and can be obtained under license for commercial applications. The executable can be requested from the Norwegian Institute for Water Research (NIVA) at
Operating Requirements
INCA-P is a 32-bit Microsoft Windows application written in C++. It is available as a command-line version (1.27 MB) or with a graphical user interface (3.75 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 phosphorus loss at different timescales in response to environmental change and catchment management
Key Output Variables
Stream flow, sediment and phosphorus concentrations and loads, phosphorus process loads, soil, soil water and groundwater P concentrations
Key Input Variables
DEM, climate data, land use, fertilizer application rates, sewage effluent concentrations
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

  • Jackson-Blake LA et al. 2016. The Integrated Catchment model of phosphorus dynamics (INCA-P): Description and demonstration of new model structure and equations. Env. Modelling and Software 83: 356-386.
  • INCA-P model description and example application

Input Data

  • CHESS 1 km2 gridded dataset.
  • British Survey of Fertilizer Practice
  • Land Cover Map of Scotland (2008)
  • 50m Digital Elevation Model
  • Agricultural Census Data
  • EU FP6 ENSEMBLE climate predictions
  • Sewage effluent data
  • Observed river flows and stream water phosphorus concentrations

Output Data

  • Daily time series of Flow, Stream water suspended sediment concentration, Stream water total phosphorus concentration, Stream water total dissolved phosphorus concentration, Stream water particulate phosphorus concentration

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