Affdef is a spatially-distributed, DEM based, continuosly (in time) simulating rainfall-runoff model, written in Fortran programming language. Affdef is raster-based. It takes as input the digital elevation model (dem) of the basin in raster form, as a rectangular matrix covering the all basin. The cells of the dem can be of any size. It needs also in input rainfall and temperature data collected in a arbitrary number of termometers and raingauges. The model computes the local contribution at the surface runoff by applying a modified CN method. In order to compute the soil storativity, the users needs to provide a matrix of CN numbers for any given dem cell. The local contribution to the surface runoff and the groundwater flows are transferred to the basin outlet by using a Muskingum-Cunge model with variable parameters.
Affdef is not deemed to be a sophisticated model, since priority was given to provide a model which is able to perform very long river flow simulations in a limited computing time. Therefore a number of conceptual schemes were used in modelling the rainfall-runoff transformation and the model cannot be considered physically-based in the strict sense. Although it can be used for any kind of basin, it should be noted that Affdef models in a simplified solution the contribution of groundwater flows. Therefore it is best suited for basins where the runoff production is mainly due to infiltration excess.
Here you can find a paper describing the model in detail. A user guide is provided here. The affdef source code can be downloaded here (zip file). A set of test data, referred to a river basin located in Italy, can be downloaded here. An executable is provided also in win32 bynary format. Please note that it can be used only for the test application. If you wish to apply the model on your own case-study, you will need to re-compile the code.
Please note that an automatic calibration procedure is available which makes use of a genethic algorithm to optimise the parameters.
The code should be user friendly. However, the program is certainly affected by bugs, since extended tests are on-going. Please contact myself should you experience any problem.
Please drop us an e-mail if you download the code. We would like to keep track of potential users, so that we can advise them about any bug we find or any improvement apported to the code.

PLEASE NOTE: a modified version of the code was prepared to allow compilation with the Unix/Linux compiler f95. Please download the modified source code here (zip file) and the set of test data here. Compilation can be done with the command line f95 *.for and will produce a linux executable file named a.out which can be run with the command line ./a.out. The new source code should work under windows as well and therefore could replace the code given above. However, I prefer to maintain both version as an extensive check of the linux version was not done yet. Please let me know if you experience any problem.