PyTOPKAPI is a BSD licensed Python library implementing the TOPKAPI Hydrological model (Liu and Todini, 2002). The model is a physically-based and fully distributed hydrological model, which has already been successfully applied in several countries around the world (Liu and Todini, 2002; Bartholomes and Todini, 2005; Liu et al., 2005; Martina et al., 2006; Vischel et al., 2008, Sinclair and Pegram, 2010).

The main strengths of the TOPKAPI model are:

• The physical basis of the equations,
• the fine-scale representation of the spatial catchment features,
• the parsimonious parametrisation linked to field/catchment information,
• the good computation time performance,
• the modularity of the processes,
• the ease of use.

These and the good results obtained in modelling the river discharges of Liebenbergsvlei catchment, make the TOPKAPI model a promising tool for hydrological modelling of catchments in South Africa and around the world.