Also known as
Model type Modular
Model part of larger framework
Note on status model
Date note status model
Incorporated models or components:
Spatial dimensions 2D
Spatial extent Landscape-Scale, Watershed-Scale
Model domain Terrestrial, Hydrology
One-line model description Physically based, distributed watershed model that simulates hydrologic fluxes of water through a watershed
Extended model description TOPMODEL is a physically based, distributed watershed model that simulates hydrologic fluxes of water (infiltration-excess overland flow, saturation overland flow, infiltration, exfiltration, subsurface flow, evapotranspiration, and channel routing) through a watershed. The model simulates explicit groundwater/surface water interactions by predicting the movement of the water table, which determines where saturated land-surface areas develop and have the potential to produce saturation overland flow.

basin, hydrological,

Name Keith Beven
Type of contact Model developer
Institute / Organization Lancaster University, Department of Environmental Science, Institute of Environmental and Natural Sciences
Postal address 1
Postal address 2
Town / City Lancaster
Postal code LA1 4YQ
Country United Kingdom
Email address
Phone +44 (0)1524 593892

Supported platforms
Other platform
Programming language


Other program language Visual Basic
Code optimized Single Processor
Multiple processors implemented
Nr of distributed processors
Nr of shared processors
Start year development 1974
Does model development still take place? Yes
If above answer is no, provide end year model development
Code development status Active
When did you indicate the 'code development status'? 2020
Model availability As code
Source code availability
(Or provide future intension)
Through web repository
Source web address
Source csdms web address
Program license type Other
Program license type other NOT SURE
Memory requirements --
Typical run time Minutes

Describe input parameters Model Inputs:
  • Project file: Text description of application and input file names and paths.
  • Catchment (watershed) data file: Watershed and subwatershed topographic index—ln(a/tan B) distributions and the following parameters:
    • The mean soil surface transmissivity
    • A transmissivity profile decay coefficient
    • A root zone storage capacity
    • An unsaturated zone time delay
    • A main channel routing velocity and internal subwatershed routing velocity

To use the infiltration excess mechanism, a hydraulic conductivity (or distribution), a wetting front suction and the initial near surface water content should be added.

The initialization of each run requires an initial stream discharge and the root zone deficit.

  • Hydrological input data file: rainfall, potential evapotranspiration, and observed discharge time series in m/h
  • Topographic index map data file: the topographic index map may be prepared from a raster digital elevation file using the DTM-ANALYSIS program. This file includes number of pixels in X direction, number of pixels in Y direction, grid size, and topographic index values for each pair of X and Y.
Input format ASCII, Binary
Other input format
Describe output parameters Model Interface Capabilities:

There are three options available in the program interface:

  • The Hydrograph Prediction Option: This option allows the model to be run and hydrographs displayed. If a Topographic Index Map File is available, then a map button is displayed that allows the display of predicted simulation, either as a summary over all timesteps or animated.
  • The Sensitivity Analysis Option: This screen allows the sensitivity of the objective functions to changes of one or more of the parameters to be explored.
  • The Monte Carlo Analysis Option: In this option a large number of runs of the model can be made using uniform random samples of the parameters chosen for inclusion in the analysis. Check boxes can be used to choose the variables and objective functions to be saved for each run. The results file produced will be compatible with the GLUE analysis software package.
Output format ASCII, Binary
Other output format
Pre-processing software needed? No
Describe pre-processing software
Post-processing software needed? Yes
Describe post-processing software TOPMODEL is integrated in GRASS GIS version 5. TOPSIMPL, another Windows version of the model written by Georges-Marie Saulnier can be downloaded directly from the main TOPMODEL site
Visualization software needed? No
If above answer is yes
Other visualization software

Describe processes represented by the model TOPMODEL is defined as a variable contributing area conceptual model in which the dynamics of surface and subsurface saturated areas is estimated on the basis of storage discharge relationships established from a simplified steady state theory for downslope saturated zone flows. The theory assumes that the local hydraulic gradient is equal to the local surface slope and implies that all points with the same value of the topographic index, a/tan B will respond in a hydrologically similar way. This index is derived from the basin topography, where a is the drained area per unit contour length and tan B is the slope of the ground surface at the location. Thus the model need make calculations only for representative values of the index. The results may then be mapped back into space by knowledge of the pattern of the index derived from a topographic analysis.
Describe key physical parameters and equations
Describe length scale and resolution constraints see the discussion of limitations in Beven et al., 1995 and Beven, 1997.

Grid or subwatersheds

Describe time scale and resolution constraints see the discussion of limitations in Beven et al., 1995 and Beven, 1997.

Variable, from 1 to 24 hours

Describe any numerical limitations and issues Model Limitations
  • TOPMODEL only simulates watershed hydrology, although studies have been conducted to modify it to

simulate water quality dynamics.

  • TOPMODEL can be applied most accurately to watersheds that do not suffer from excessively long dry

periods and have shallow homogeneous soils and moderate topography.

  • Model results are sensitive to grid size, and grid size <=50 m is recommended.

Describe available calibration data sets TOPMODEL calibration procedures are relatively simple because it uses very few parameters in the model formulas. The model is very sensitive to changes of the soil hydraulic conductivity decay parameter, the soil transmissivity at saturation, the root zone storage capacity, and the channel routing velocity in larger watersheds. The calibrated values of parameters are also related to the grid size used in the digital terrain analysis. The timestep and the grid size also have been shown to influence TOPMODEL simulations.
Upload calibration data sets if available:
Describe available test data sets Example of TOPMODEL simulation
Upload test data sets if available: Media:TOPMODEL
Describe ideal data for testing

Do you have current or future plans for collaborating with other researchers? --
Is there a manual available? No
Upload manual if available:
Model website if any
Model forum / discussion board
Comments Linkages Supported: Links to GLUE (Generalized Likelihood Uncertainty Estimation) program for sensitivity/uncertainty/calibration analyses.

This part will be filled out by CSDMS staff

OpenMI compliant No but possible
BMI compliant No but possible
WMT component No but possible
PyMT component
Is this a data component
Can be coupled with:
Model info
Keith Beven
Nr. of publications: 565
Total citations: 31999
h-index: 89
m-quotient: 2.23
Qrcode TOPMODEL.png
Link to this page




Nr. of publications: 565
Total citations: 31999
h-index: 89
m-quotient: 2.23

Featured publication(s)YearModel describedType of ReferenceCitations
Beven, Keith; 1997. TOPMODEL: A critique. Hydrological Processes, 11, 1069–1085. 10.1002/(SICI)1099-1085(199707)11:93.0.CO;2-O
(View/edit entry)
Model overview 584
Ambroise, Bruno; Beven, Keith; Freer, Jim; 1996. Toward a Generalization of the TOPMODEL Concepts: Topographic Indices of Hydrological Similarity. Water Resources Research, 32, 2135–2145. 10.1029/95WR03716
(View/edit entry)
Model overview 316
Beven, Keith; Freer, Jim; 2001. A dynamic TOPMODEL. Hydrological Processes, 15, 1993–2011. 10.1002/hyp.252
(View/edit entry)
Model overview 333
See more publications of TOPMODEL



Input Files

Output Files