The rocky outcrops in the Venezuelan Andean páramo constitute a geomorphological unit with a considerable area. The hydrologic processes of this source area are not represented by the TOPMODEL. This study aimed to improve the hydrological simulation of  the TOPMODEL, specifically the description of overland flow, by incorporating flow of this type generated by the rocky source area. Based on the analysis of various researches a parameter a was introduced redirecting to overland flow a fraction of the precipitation falling on the rocky outcrops. This parameter was calibrated, what led to an improvement in Nash-Sutcliffe efficiency in the model calibration and validation phase. Assuming a runoff coefficient of 1 in the outcrops and according to the calibration, the rainfall that falls on 25% of the outcrop areas is redirected, possibly it is the set of outcrops located at most 44 m from the drainage network. However, other interpretations are possible, what requires further research.