INCA Methods

INCA logoThe INCA model has been designed to investigate the fate and distribution of chemicals in the aquatic and terrestrial environment. The model simulates flow and water quality and tracks the flow paths operating in both the land phase and riverine phase. The model is dynamic in that the day-to-day variations in flow and water quality can be investigated following a change in input conditions form point or diffuse sources such as atmospheric deposition, sewage discharges or fertiliser addition. The model can also be used to investigate a change in land use (e.g. moorland to forest or pasture to arable) or a change in climatic conditions. Dilution, natural decay and biochemical transformation processes are included in the model as well as the interactions with plant biomass such as nutrient uptake by vegetation on the land surface or macrophytes in streams.

INCA catchment map 3DINCA has been designed to be easy to use and fast, with excellent output graphics. The menu system allows the user to specify the semi-distributed nature of a river basin or catchment, to alter reach lengths, rate coefficients, land use, velocity-flow relationships and to vary input loads.

INCA provides the following outputs:

  • daily time series of flows, water quality concentrations at selected sites along the river;
  • profiles of flow or water quality along the river at selected times;
  • cumulative frequency distributions of flow and water quality at selected sites;
  • tables of statistics for all sites;
  • daily and annual pollution loads for all land uses and all processes.

The software is available as a windows package and can be obtained from the University of Reading. Contact Professor Andrew Wade ( or Professor Paul Whitehead (

Original References for Overall Model Philosophy

  • 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.

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Professor Andrew Wade

Postal address:

Department of Geography and Environmental Science,
University of Reading,
RG6 6AB,


 +44 (0)118 931 7315

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